ALBERT

Description: A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816 Climate of the Past, 11, 1027-1047, 2015 Author(s): Y. Brugnara, R. Auchmann, S. Brönnimann, R. J. Allan, I. Auer, M. Barriendos, H. Bergström, J. Bhend, R. Brázdil, G. P. Compo, R. C. Cornes, F. Dominguez-Castro, A. F. V. van Engelen, J. Filipiak, J. Holopainen, S. Jourdain, M. Kunz, J. Luterbacher, M. Maugeri, L. Mercalli, A. Moberg, C. J. Mock, G. Pichard, L. Řezníčková, G. van der Schrier, V. Slonosky, Z. Ustrnul, M. A. Valente, A. Wypych, and X. Yin The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.

Description: Bottom water variability in the subtropical northwestern Pacific from 26 kyr BP to present based on Mg / Ca and stable carbon and oxygen isotopes of benthic foraminifera Climate of the Past, 11, 803-824, 2015 Author(s): Y. Kubota, K. Kimoto, T. Itaki, Y. Yokoyama, Y. Miyairi, and H. Matsuzaki To understand bottom water variability in the subtropical northwestern Pacific, bottom water temperatures (BWTs), carbon isotopes (δ 13 C), and oxygen isotopes of seawater (δ 18 O w ) at a water depth of 1166 m were reconstructed from 26 kyr BP to present. A new regional Mg / Ca calibration for the benthic foraminifera Cibicidoides wuellerstorfi (type B) was established to convert the benthic Mg / Ca value to BWT, based on 26 surface sediment samples and two core-top samples retrieved around Okinawa Island. During the Last Glacial Maximum (LGM), the δ 18 O w in the intermediate water in the northwestern South Pacific was ~0.4‰ lower than in the deep South Pacific, indicating a greater vertical salinity gradient than at present. This salinity (and probably density) structure would have led to stratification in the intermediate and deep Pacific, which would, in turn, have greatly influenced carbon storage during the glacial time. The benthic Mg / Ca and δ 18 O w records suggest changes that seem to follow Heinrich event 1 (H1) and the Bølling–Alleød (B/A) and Younger Dryas (YD) intervals, with BWT higher during H1 (~17 kyr BP) and YD (~12 kyr BP) and lower during B/A (~14 kyr BP). The warming in the bottom water during H1 suggests increased contribution of North Pacific Intermediate Water (NPIW) to the subtropical northwestern Pacific and decreased upwelling of cooler waters from the abyssal North Pacific. During the interval from 17 to 14.5 kyr BP, the BWT tended to decrease successively in association with a decrease in δ 13 C values, presumably as a result of increased upwelling of the abyssal waters to the intermediate depths of the North Pacific caused by shoaling and enhancement of the southward return flow of Pacific Deep Water (PDW). During the Holocene, the millennial- to sub-millennial-scale variations in the BWT generally correlate with the sea surface temperatures in the Okhotsk Sea, the source region of the NPIW, suggesting that changes in the BWT are linked to changes in the NPIW production rate.

Description: Coupled Northern Hemisphere permafrost–ice-sheet evolution over the last glacial cycle Climate of the Past, 11, 1165-1180, 2015 Author(s): M. Willeit and A. Ganopolski Permafrost influences a number of processes which are relevant for local and global climate. For example, it is well known that permafrost plays an important role in global carbon and methane cycles. Less is known about the interaction between permafrost and ice sheets. In this study a permafrost module is included in the Earth system model CLIMBER-2, and the coupled Northern Hemisphere (NH) permafrost–ice-sheet evolution over the last glacial cycle is explored. The model performs generally well at reproducing present-day permafrost extent and thickness. Modeled permafrost thickness is sensitive to the values of ground porosity, thermal conductivity and geothermal heat flux. Permafrost extent at the Last Glacial Maximum (LGM) agrees well with reconstructions and previous modeling estimates. Present-day permafrost thickness is far from equilibrium over deep permafrost regions. Over central Siberia and the Arctic Archipelago permafrost is presently up to 200–500 m thicker than it would be at equilibrium. In these areas, present-day permafrost depth strongly depends on the past climate history and simulations indicate that deep permafrost has a memory of surface temperature variations going back to at least 800 ka. Over the last glacial cycle permafrost has a relatively modest impact on simulated NH ice sheet volume except at LGM, when including permafrost increases ice volume by about 15 m sea level equivalent in our model. This is explained by a delayed melting of the ice base from below by the geothermal heat flux when the ice sheet sits on a porous sediment layer and permafrost has to be melted first. Permafrost affects ice sheet dynamics only when ice extends over areas covered by thick sediments, which is the case at LGM.

Description: Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes Climate of the Past, 11, 1197-1222, 2015 Author(s): P. J. Bartlein, M. E. Edwards, S. W. Hostetler, S. L. Shafer, P. M. Anderson, L. B. Brubaker, and A. V. Lozhkin Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-observations. The subcontinental region of Beringia (northeastern Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering–Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present-day simulations of regional climate – one with modern and one with 11 ka geography – plus another simulation for 6 ka. In addition, we performed five ~ 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka Control , which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present-day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal vegetation types distributed as suggested by the paleoecological record, (iv) thaw lakes, which used the present-day distribution of lakes and wetlands, and (v) post-11 ka All , incorporating all boundary conditions changed in experiments (ii)–(iv). We find that regional-scale controls strongly mediate the climate responses to changes in the large-scale controls, amplifying them in some cases, damping them in others, and, overall, generating considerable spatial heterogeneity in the simulated climate changes. The change from tundra to deciduous woodland produces additional widespread warming in spring and early summer over that induced by the 11 ka insolation regime alone, and lakes and wetlands produce modest and localized cooling in summer and warming in winter. The greatest effect is the flooding of the land bridge and shelves, which produces generally cooler conditions in summer but warmer conditions in winter and is most clearly manifest on the flooded shelves and in eastern Beringia. By 6 ka continued amplification of the seasonal cycle of insolation and loss of the Laurentide ice sheet produce temperatures similar to or higher than those at 11 ka, plus a longer growing season.

Description: Transitivity of the climate–vegetation system in a warm climate Climate of the Past, 11, 1563-1574, 2015 Author(s): U. Port and M. Claussen To date, the transitivity of the global system has been analysed for late Quaternary (glacial, interglacial, and present-day) climate. Here, we extend this analysis to a warm, almost ice-free climate with a different configuration of continents. We use the Earth system model of the Max Planck Institute for Meteorology to analyse the stability of the climate system under early Eocene and pre-industrial conditions. We initialize the simulations by prescribing either dense forests or bare deserts on all continents. Starting with desert continents, an extended desert remains in central Asia in the early Eocene climate. Starting with dense forest coverage, the Asian desert is much smaller, while coastal deserts develop in the Americas which appear to be larger than in the simulations with initially bare continents. These differences can be attributed to differences in the large-scale tropical circulation. With initially forested continents, a stronger dipole in the 200 hPa velocity potential develops than in the simulation with initially bare continents. This difference prevails when vegetation is allowed to adjust to and interact with climate. Further simulations with initial surface conditions that differ in the region of the Asian desert only indicate that local feedback processes are less important in the development of multiple states. In the interglacial, pre-industrial climate, multiple states develop only in the Sahel region. There, local climate–vegetation interaction seems to dominate.

Description: How might the North American ice sheet influence the northwestern Eurasian climate? Climate of the Past, 11, 1467-1490, 2015 Author(s): P. Beghin, S. Charbit, C. Dumas, M. Kageyama, and C. Ritz It is now widely acknowledged that past Northern Hemisphere ice sheets covering Canada and northern Europe at the Last Glacial Maximum (LGM) exerted a strong influence on climate by causing changes in atmospheric and oceanic circulations. In turn, these changes may have impacted the development of the ice sheets themselves through a combination of different feedback mechanisms. The present study is designed to investigate the potential impact of the North American ice sheet on the surface mass balance (SMB) of the Eurasian ice sheet driven by simulated changes in the past glacial atmospheric circulation. Using the LMDZ5 atmospheric circulation model, we carried out 12 experiments under constant LGM conditions for insolation, greenhouse gases and ocean. In these experiments, the Eurasian ice sheet is removed. The 12 experiments differ in the North American ice-sheet topography, ranging from a white and flat (present-day topography) ice sheet to a full-size LGM ice sheet. This experimental design allows the albedo and the topographic impacts of the North American ice sheet onto the climate to be disentangled. The results are compared to our baseline experiment where both the North American and the Eurasian ice sheets have been removed. In summer, the sole albedo effect of the American ice sheet modifies the pattern of planetary waves with respect to the no-ice-sheet case, resulting in a cooling of the northwestern Eurasian region. By contrast, the atmospheric circulation changes induced by the topography of the North American ice sheet lead to a strong decrease of this cooling. In winter, the Scandinavian and the Barents–Kara regions respond differently to the American ice-sheet albedo effect: in response to atmospheric circulation changes, Scandinavia becomes warmer and total precipitation is more abundant, whereas the Barents–Kara area becomes cooler with a decrease of convective processes, causing a decrease of total precipitation. The gradual increase of the altitude of the American ice sheet leads to less total precipitation and snowfall and to colder temperatures over both the Scandinavian and the Barents and Kara sea sectors. We then compute the resulting annual surface mass balance over the Fennoscandian region from the simulated temperature and precipitation fields used to force an ice-sheet model. It clearly appears that the SMB is dominated by the ablation signal. In response to the summer cooling induced by the American ice-sheet albedo, high positive SMB values are obtained over the Eurasian region, leading thus to the growth of an ice sheet. On the contrary, the gradual increase of the American ice-sheet altitude induces more ablation over the Eurasian sector, hence limiting the growth of Fennoscandia. To test the robustness of our results with respect to the Eurasian ice sheet state, we carried out two additional LMDZ experiments with new boundary conditions involving both the American (flat or full LGM) and high Eurasian ice sheets. The most striking result is that the Eurasian ice sheet is maintained under full-LGM North American ice-sheet conditions, but loses ~ 10 % of its mass compared to the case in which the North American ice sheet is flat. These new findings qualitatively confirm the conclusions from our first series of experiments and suggest that the development of the Eurasian ice sheet may have been slowed down by the growth of the American ice sheet, offering thereby a new understanding of the evolution of Northern Hemisphere ice sheets throughout glacial–interglacial cycles.

Description: A 500-year seasonally resolved δ 18 O and δ 13 C, layer thickness and calcite aspect record from a speleothem deposited in the Han-sur-Lesse cave, Belgium Climate of the Past, 11, 789-802, 2015 Author(s): M. Van Rampelbergh, S. Verheyden, M. Allan, Y. Quinif, H. Cheng, L. R. Edwards, E. Keppens, and P. Claeys Speleothem δ 18 O and δ 13 C signals enable climate reconstructions at high resolution. However, scarce decadal and seasonally resolved speleothem records are often difficult to interpret in terms of climate due to the multitude of factors that affect the proxy signals. In this paper, a fast-growing (up to 2 mm yr −1 ) seasonally laminated speleothem from the Han-sur-Lesse cave (Belgium) is analyzed for its δ 18 O and δ 13 C values, layer thickness and changes in calcite aspect. The studied record covers the period between AD 2001 and 1479 as indicated by layer counting and confirmed by 20 U / Th ages. The Proserpine proxies are seasonally biased and document drier (and colder) winters on multidecadal scales. Higher δ 13 C signals reflect increased prior calcite precipitation (PCP) and lower soil activity during drier (and colder) winters. Thinner layers and darker calcite relate to slower growth and exist during drier (and colder) winter periods. Exceptionally dry (and cold) winter periods occur from 1565 to 1610, at 1730, from 1770 to 1800, from 1810 to 1860, and from 1880 to 1895 and correspond to exceptionally cold periods in historical and instrumental records as well as European winter temperature reconstructions. More relative climate variations, during which the four measured proxies vary independently and display lower amplitude variations, occur between 1479 and 1565, between 1610 and 1730, and between 1730 and 1770. The winters during the first and last periods are interpreted as relatively wetter (and warmer) and correspond to warmer periods in historical data and in winter temperature reconstructions in Europe. The winters in the period between 1610 and 1730 are interpreted as relatively drier (and cooler) and correspond to generally colder conditions in Europe. Interpretation of the seasonal variations in δ 18 O and δ 13 C signals differs from that on a decadal and multidecadal scale. Seasonal δ 18 O variations reflect cave air temperature variations and suggest a 2.5 °C seasonality in cave air temperature during the two relatively wetter (and warmer) winter periods (1479–1565 and 1730–1770), which corresponds to the cave air temperature seasonality observed today. Between 1610 and 1730, the δ 18 O values suggest a 1.5 °C seasonality in cave air temperature, indicating colder summer temperatures during this drier (and cooler) interval. The δ 13 C seasonality is driven by PCP and suggests generally lower PCP seasonal effects between 1479 and 1810 compared to today. A short interval of increased PCP seasonality occurs between 1600 and 1660, and reflects increased PCP in summer due to decreased winter recharge.

Description: Controls on fire activity over the Holocene Climate of the Past, 11, 781-788, 2015 Author(s): S. Kloster, T. Brücher, V. Brovkin, and S. Wilkenskjeld Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed, which react differently to changes in climate. Disentangling these controlling factors helps in understanding the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP, with larger regional changes compensating nearly evening out on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental-scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia monsoon, Central America tropics/subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such, observed changes in fire activity cannot be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help in understanding the climate control on fire activity, which is essential to project future fire activity.

Description: Boreal fire records in Northern Hemisphere ice cores: A review Michel Legrand, Joseph McConnell, Hubertus Fischer, Eric W. Wolff, Susanne Preunkert, Nathan Chellman, Daiana Leuenberger, Olivia Maselli, Michael Sigl, Simon Schüpbach, and Mike Flannigan Clim. Past Discuss., doi:10.5194/cp-2016-70,2016 Manuscript under review for CP (discussion: open, 0 comments) Here we review previous attempts made to reconstruct past forest fire using chemical signals recorded in Greenland ice. We showed that the Greenland ice records of ammonium, found to be a good fire proxy, consistently indicate changing fire activity in Canada in response to past climatic conditions that occurred since the last 15 000 years including the little ice age and the last large climatic transition.

Description: Palynological evidence for late Miocene stepwise aridification on the northeastern Tibetan Plateau Jia Liu, Ji Jun Li, Chun Hui Song, Hao Yu, Ting Jiang Peng, Zheng Chuang Hui, and Xi Yan Ye Clim. Past, 12, 1473-1484, doi:10.5194/cp-12-1473-2016, 2016 The late Cenozoic basins in the northeastern Tibetan Plateau document both the tectonic uplift process and its associated environmental changes. Here, we investigated a late Miocene sporopollen record from the Tianshui Basin in the northeastern Tibetan Plateau. The results show that a persistent aridification trend parallels the global cooling of the late Miocene, and the stepwise vegetation succession is consistent with the major uplift events of the Tibetan Plateau.

Description: Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt Maria-Angela Bassetti, Serge Berné, Marie-Alexandrine Sicre, Bernard Dennielou, Yoann Alonso, Roselyne Buscail, Bassem Jalali, Bertil Hebert, and Christophe Menniti Clim. Past, 12, 1539-1553, doi:10.5194/cp-12-1539-2016, 2016 This work represents the first attempt to decipher the linkages between rapid climate changes and continental Holocene paleohydrology in the NW Mediterranean shallow marine setting. Between 11 and 4 ka cal BP, terrigenous input increased and reached a maximum at 7 ka cal BP, probably as a result of a humid phase. From ca. 4 ka cal BP to the present, enhanced variability in the land-derived material is possibly due to large-scale atmospheric circulation and rainfall patterns in western Europe.

Description: Regional climate signal vs. local noise: a two-dimensional view of water isotopes in Antarctic firn at Kohnen Station, Dronning Maud Land Thomas Münch, Sepp Kipfstuhl, Johannes Freitag, Hanno Meyer, and Thomas Laepple Clim. Past, 12, 1565-1581, doi:10.5194/cp-12-1565-2016, 2016 Ice-core oxygen isotope ratios are a key climate archive to infer past temperatures, an interpretation however complicated by non-climatic noise. Based on 50 m firn trenches, we present for the first time a two-dimensional view (vertical × horizontal) of how oxygen isotopes are stored in Antarctic firn. A statistical noise model allows inferences for the validity of ice coring efforts to reconstruct past temperatures, highlighting the need of replicate cores for Holocene climate reconstructions.

Description: An improved North-South synchronization of ice core records around the 41 K beryllium 10 peak G. M. Raisbeck, A. Cauquoin, J. Jouzel, A. Landais, J.-R. Petit, V. Y. Lipenkov, J. Beer, H.-A. Synal, H. Oerter, S. J. Johnsen, J. P. Steffensen, A. Svensson, and F. Yiou Clim. Past Discuss., doi:10.5194/cp-2016-79,2016 Manuscript under review for CP (discussion: open, 0 comments) Using records of a long lived radioactive nuclide ( 10 Be) that is formed globally in the atmosphere and deposited within a few years to the earth's surface, we have synchronized 3 Antarctic ice cores to one from Greenland. This permits the climate and other environmental parameters registered in these ice cores to be put on a common time scale with a precision of a few decades, thus allowing different models and mechanisms associated with these parameters to be tested with the same precision.

Description: Freshening of the Labrador Sea as a trigger for Little Ice Age development Montserrat Alonso-Garcia, Helga F. Kleiven, Jerry F. McManus, Paola Moffa-Sanchez, Wallace Broecker, and Benjamin P. Flower Clim. Past Discuss., doi:10.5194/cp-2016-80,2016 Manuscript under review for CP (discussion: open, 0 comments) This study focuses on understanding climatic and oceanographic variations that took place during the last 1000 years. We studied sediment samples from the Labrador Sea looking for evidence of events of freshwater and iceberg discharges to this region. The importance of this study is to evaluate when these events happened and its possible consequences. The freshening of the Labrador Sea region may have played a major role on the cooling underwent during the 15th to 19th centuries.

Description: The role of basal hydrology in the surging of the Laurentide Ice Sheet William H. G. Roberts, Antony J. Payne, and Paul J. Valdes Clim. Past, 12, 1601-1617, doi:10.5194/cp-12-1601-2016, 2016 There are observations from ocean sediment cores that during the last ice age the Laurentide Ice Sheet, which sat over North America, periodically surged. In this study we show the role that water at the base of an ice sheet plays in these surges. We show that with a more realistic representation of water drainage at the base of the ice sheet than usually used, these surges can still occur and that they are triggered by an internal ice sheet instability; no external trigger is needed.

Description: North American regional climate reconstruction from Ground Surface Temperature Histories Fernando Jaume-Santero, Carolyne Pickler, Hugo Beltrami, and Jean-Claude Mareschal Clim. Past Discuss., doi:10.5194/cp-2016-85,2016 Manuscript under review for CP (discussion: open, 0 comments) Within the framework of the PAGES NAm2k project, we estimated regional trends in the ground surface temperature change for the past 500 years in North America. The mean North American ground surface temperature history suggests a warming of 1.8 °C between preindustrial times and 2000. A regional analysis of mean temperature changes over the last 5 centuries shows that all regions experienced warming, but this warming displays large spatial variability, and is more marked in high latitude regions.

Description: The 1816 ‘year without a summer’ in an atmospheric reanalysis Philip Brohan, Gilbert P. Compo, Stefan Brönnimann, Robert J. Allan, Renate Auchmann, Yuri Brugnara, Prashant D. Sardeshmukh, and Jeffrey S. Whitaker Clim. Past Discuss., doi:10.5194/cp-2016-78,2016 Manuscript under review for CP (discussion: open, 0 comments) We have used modern weather forecasting tools to reconstruct the dreadful European weather of 200 years ago – 1816 was the ‘year without a summer’; harvests failed, and people starved. We can show that 1816’s extreme climate was caused by the eruption of the Tambora volcano the previous year. This means we have some chance of predicting such extreme summers if they occur in future, though this is still a challenge to today’s forecast models.

Description: North Atlantic Oscillation controls on oxygen and hydrogen isotope gradients in winter precipitation across Europe; implications for palaeoclimate studies Michael Deininger, Martin Werner, and Frank McDermott Clim. Past Discuss., doi:10.5194/cp-2016-77,2016 Manuscript under review for CP (discussion: open, 0 comments) This study investigates the NAO-related mechanisms that control winter-precipitation stable oxygen and hydrogen isotope gradients across Europe. The results show that past longitudinal stable oxygen and hydrogen isotope gradients in European rainfall stored in palaeoclimate archives (e.g. speleothems) can be used to infer the past winter NAO modes from its variations.

Description: Influence of proxy data uncertainty on data assimilation for the past climate Anastasios Matsikaris, Martin Widmann, and Johann Jungclaus Clim. Past, 12, 1555-1563, doi:10.5194/cp-12-1555-2016, 2016 We have assimilated proxy-based (PAGES 2K) and instrumental (HadCRUT3v) observations into a General Circulation Model (MPI-ESM-CR). Assimilating instrumental data improves the performance of Data Assimilation. No skill on small spatial scales is however found for either of the two schemes. Errors in the assimilated data are therefore not the main reason for this lack of skill; continental mean temperatures cannot provide skill on small spatial scales in palaeoclimate reconstructions.

Description: Quantification of southwest China rainfall during the 8.2 ka BP event with response to North Atlantic cooling Yuhui Liu and Chaoyong Hu Clim. Past, 12, 1583-1590, doi:10.5194/cp-12-1583-2016, 2016 The 8.2 ka BP event, a global climate anomaly that occurred 8200 years ago, could provide climate teleconnection information for the simulation of abrupt climate changes, but there are few quantitative reconstructions of this event. This paper provides a 10-year resolution rainfall record from the East Asian monsoon area during the event, showing the reduced rainfall in southwest China during the 8.2 ka BP period was coupled with Greenland cooling with a possible response rate of 110 ± 30 mm/℃.

Description: Could the Pliocene constrain the equilibrium climate sensitivity? J. C. Hargreaves and J. D. Annan Clim. Past, 12, 1591-1599, doi:10.5194/cp-12-1591-2016, 2016 The mid-Pliocene Warm Period, 3 million years ago, was the most recent interval with high greenhouse gases. By modelling the period with the same models used for future projections, we can link the past and future climates. Here we use data from the mid-Pliocene to produce a tentative result for equilibrium climate sensitivity. We show that there are considerable uncertainties that strongly influence the result, but we are optimistic that these may be reduced in the next few years.

Description: Multi-timescale data assimilation for atmosphere–ocean state estimates Nathan Steiger and Gregory Hakim Clim. Past, 12, 1375-1388, doi:10.5194/cp-12-1375-2016, 2016 We present a data assimilation algorithm that incorporates proxy data at arbitrary timescales. Within a synthetic-test framework, we find that atmosphere–ocean states are most skillfully reconstructed by incorporating proxies across multiple timescales compared to using them at short or long timescales alone. Additionally, reconstructions that incorporate long-timescale proxies improve the low-frequency components of the reconstructions relative to using only high-resolution proxies.

Description: Holocene biome changes in Asia – an analysis of different transient Earth system model simulations Anne Dallmeyer, Martin Claussen, Jian Ni, Xianyong Cao, Yongbo Wang, Nils Fischer, Madlen Pfeiffer, Liya Jin, Vyacheslav Khon, Sebastian Wagner, Kerstin Haberkorn, and Ulrike Herzschuh Clim. Past Discuss., doi:10.5194/cp-2016-67,2016 Manuscript under review for CP (discussion: open, 0 comments) The vegetation distribution in Eastern Asia is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate-vegetation relationship is lacking. To assess the Holocene vegetation change, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient climate simulations.

Description: Glacial δ 13 C decreases in the western South Atlantic forced by millennial changes in Southern Ocean ventilation Marília C. Campos, Cristiano M. Chiessi, Ines Voigt, Alberto R. Piola, Henning Kuhnert, and Stefan Mulitza Clim. Past Discuss., doi:10.5194/cp-2016-59,2016 Manuscript under review for CP (discussion: open, 0 comments) Abrupt climate change events of the last deglaciation were accompanied by increases in atmospheric CO 2 presumably originated by outgassing from the Southern Ocean. We present new planktonic foraminiferal stable carbon isotopic data from the western South Atlantic that suggest that the CO 2 added to the atmosphere during abrupt climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing from the Southern Ocean.

Description: Jens Esmark's Christiania (Oslo) meteorological observations 1816–1838: The first long term continuous temperature record from the Norwegian capital homogenized and analysed Geir Hestmark and Øyvind Nordli Clim. Past Discuss., doi:10.5194/cp-2016-60,2016 Manuscript under review for CP (discussion: open, 0 comments) The detailed and continuous meteorological observations of professor Jens Esmark from the capital of Norway in the period 1816 to 1838 are evaluated, homogenized and reanalyzed with modern methods to characterize the weather in Oslo in this period.

Description: Large-scale drivers of Caucasus climate variability in meteorological records and Mt Elbrus ice cores Anna Kozachek, Vladimir Mikhalenko, Valérie Masson-Delmotte, Alexey Ekaykin, Patrick Ginot, Stanislav Kutuzov, Michel Legrand, Vladimir Lipenkov, and Susanne Preunkert Clim. Past Discuss., doi:10.5194/cp-2016-62,2016 Manuscript under review for CP (discussion: open, 0 comments) A 181.2 m ice core was recovered from a borehole drilled into bedrock on the western plateau of Mt. Elbrus (43°20’53.9’’ N, 42°25’36.0’’ E; 5115 m a.s.l.) in the Caucasus, Russia, in 2009 (Mikhalenko et al., 2015). Here, we report on the results of the water stable isotope composition from this ice core in comparison with results from shallow ice cores. There is a distinct seasonal cycle of the isotopic composition which allowed dating by annual layer counting. Dating has been performed for the upper 126 m of the deep core combined with shallow cores data. The whole record covers one century from 2013 back to 1914. Due to the high accumulation rate (1380 mm w.e. per year) and limited melting we obtained the isotopic composition and accumulation rate records with seasonal resolution. These values were compared with available meteorological data from 13 weather stations in the region, and also with atmosphere circulation indices, back-trajectories calculations and GNIP data in order to decipher the drivers of accumulation and ice core isotopic composition in the Caucasus region. In the summer season the isotopic composition depends on the local temperature, while in winter, the atmospheric circulation is the predominant driver of the ice core isotopic composition. The snow accumulation rate correlates well with the precipitation rate in the region all year round, this made it possible to reconstruct and expand the precipitation record at the Caucasus highlands from 1914 till 1966 when the reliable meteorological observations of precipitation at high elevation began.

Description: Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals Quentin Dubois-Dauphin, Paolo Montagna, Giuseppe Siani, Eric Douville, Claudia Wienberg, Dierk Hebbeln, Zhifei Liu, Nejib Kallel, Arnaud Dapoigny, Marie Revel, Edwige Pons-Branchu, and Christophe Colin Clim. Past Discuss., doi:10.5194/cp-2016-64,2016 Manuscript under review for CP (discussion: open, 0 comments) The neodymium isotopic composition (εNd) of mixed planktonic foraminifera species and scleractinian cold-water corals (CWC; Madrepora oculata , Lophelia pertusa ) collected at 280–620 m water depth in the Balearic Sea, the Alboran Sea and the south Sardinian continental margin was investigated to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 ka. Planktonic ( Globigerina bulloides ) and benthic ( Cibicidoides pachyderma ) foraminifera were also analyzed for stable oxygen (δ 18 O) and carbon (δ 13 C) isotopes. The foraminiferal and coral εNd values from the Balearic Sea and the Alboran Sea are comparable over the past ~ 13 ka, with mean values of −8.94 ± 0.26 (1σ; n = 24) and −8.91 ± 0.18 (1σ; n = 25), respectively. Before 13 ka BP, the foraminiferal εNd values are slightly lower (−9.28 ± 0.15) and tend to reflect a higher mixing between intermediate and deep waters, characterized by more unradiogenic εNd values. The slight εNd increase after 13 ka BP is associated to a marked difference in the benthic foraminiferal δ 13 C composition of intermediate and deeper depths, which started at ~ 16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic εNd from deep waters. The CWC from the Sardinia Channel show a much larger scattering of εNd values, from −8.66 ± 0.30 to −5.99 ± 0.50, and a lower average (−7.31 ± 0.73; n = 19) compared to the CWC and foraminifera from the Alboran Sea and Balearic Sea, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the εNd values of the Sardinian CWC become more unradiogenic (−8.38 ± 0.47; n = 3 at ~ 8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin. Accordingly, we propose here that western Mediterranean intermediate waters replaced the Levantine Intermediate Water (LIW), which was strongly reduced during the mid-sapropel (~ 8.7 ka BP). This observation supports a notable change of Mediterranean circulation pattern centered on sapropel S1 that needs further investigations to be confirmed.

Description: Climatic effects and impacts of the 1815 eruption of Mount Tambora in the Czech Lands Rudolf Brázdil, Ladislava Řezníčková, Hubert Valášek, Lukáš Dolák, and Oldřich Kotyza Clim. Past, 12, 1361-1374, doi:10.5194/cp-12-1361-2016, 2016 The paper deals with climatic and human impacts of the strong Tambora (Indonesia) volcanic eruption in April 1815 over the Czech Lands territory based on analysis of documentary data and instrumental records. While climatic effects were related particularly to summers 1815 and 1816 (1816 is known as "a Year Without Summer"), quite important were societal impacts represented after bad harvest by steep increase in prices and shortages of food.

Description: Sensitivity of Pliocene climate simulations in MRI-CGCM2.3 to respective boundary conditions Youichi Kamae, Kohei Yoshida, and Hiroaki Ueda Clim. Past Discuss., doi:10.5194/cp-2016-50,2016 Manuscript under review for CP (discussion: open, 0 comments) Climate model simulations conducted in previous studies tended to underestimate higher-latitude warming during the late Pliocene suggested by proxy evidences. We explore how prescribed trace gases, ice sheet, vegetation, lakes and orography affect the Pliocene climate simulation based on a protocol of the PlioMIP Phase 2. The revised boundary forcing data lead to amplified higher-latitude warming that is qualitatively consistent with the paleoenvironment reconstructions.

Description: Effects of melting ice sheets and orbital forcing on the early Holocene warming in the extratropical Northern Hemisphere Yurui Zhang, Hans Renssen, and Heikki Seppä Clim. Past, 12, 1119-1135, doi:10.5194/cp-12-1119-2016, 2016 We explore how forcings contributed to climate change during the early Holocene that marked the final transition to the warm and stable stage. Our results indicate that 1) temperature at the Holocene onset was lower than in the preindustrial over the northern extratropics with the exception in Alaska, and the magnitude of this cooling varies regionally as a response to varying climate forcings and diverse mechanisms, and 2) the rate of the early Holocene warming was also spatially heterogeneous.

Description: Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine O. J. Maselli, N. J. Chellman, M. Grieman, L. Layman, J. R. McConnell, D. Pasteris, R. H. Rhodes, E. Saltzman, and M. Sigl Clim. Past Discuss., doi:10.5194/cp-2016-49,2016 Manuscript under review for CP (discussion: open, 0 comments) We analyzed two Greenland ice cores for methanesulfonate (MSA) and bromine (Br) and concluded that both species are suitable proxies for local sea ice conditions. Interpretation of the records reveals that there have been sharp declines in sea ice in these areas in the past 250 years. However, at both sites the Br record deviates from MSA during the industrial period, raising questions about the value of Br as a sea ice proxy during recent periods of high, industrial atmospheric acid pollution.

Description: Spatial climate dynamics in the Iberian Peninsula since 15 000 yr BP Pedro Tarroso, José Carrión, Miriam Dorado-Valiño, Paula Queiroz, Luisa Santos, Ana Valdeolmillos-Rodríguez, Paulo Célio Alves, José Carlos Brito, and Rachid Cheddadi Clim. Past, 12, 1137-1149, doi:10.5194/cp-12-1137-2016, 2016 The climate fluctuates between warm and cold stages, forcing biodiversity to shift patterns according to climatic tolerance. Here we provide an analysis of the shifting patterns of climate in the Iberian Peninsula for the last 15 000 years. By analysing climate in the spatial and temporal dimensions, we were able to divide the peninsula into areas that shared similar climate patterns and to derive a map of climate stability for this period.

Description: Sulphur-rich volcanic eruptions triggered extreme hydrological events in Europe since AD 1850 Cristina Di Salvo and Gianluca Sottili Clim. Past Discuss., doi:10.5194/cp-2016-53,2016 Manuscript under review for CP (discussion: open, 0 comments) In Europe, intensities of hydrological extreme events were influenced by volcanic SO 2 concentrations in the Northern Hemisphere. SO 2 -rich eruptions, similar to the Bárðarbunga 2014–15 eruption (Iceland), by affecting Ocean-atmosphere heat exchange, affected the intensity of the NAO with effects on rainfall and flood intensities. SO 2 effects, superimposed to climate change, could enhance frequencies and intensities of extreme events, thus increasing the natural risks in densely populated area.

Description: A universal error source in past climate estimates derived from tree rings Juhani Rinne, Mikko Alestalo, and Jörg Franke Clim. Past Discuss., doi:10.5194/cp-2016-27,2016 Manuscript under review for CP (discussion: open, 0 comments) The climate reconstructions derived from tree rings tend to show erroneous long-term oscillations. The aim of our paper is to describe the phenomenon and to uncover its reasons. In order to derive formulae describing the long-term error, the dependence of the tree rings on the age is not used in the reconstruction. The erroneous oscillations turn out to be due to data paucities over the years. Accordingly, such long-term errors can be present in any tree ring analysis with such paucities.

Description: Arctic sea ice simulation in the PlioMIP ensemble Fergus W. Howell, Alan M. Haywood, Bette L. Otto-Bliesner, Fran Bragg, Wing-Le Chan, Mark A. Chandler, Camille Contoux, Youichi Kamae, Ayako Abe-Ouchi, Nan A. Rosenbloom, Christian Stepanek, and Zhongshi Zhang Clim. Past, 12, 749-767, doi:10.5194/cp-12-749-2016, 2016 Simulations of pre-industrial and mid-Pliocene Arctic sea ice by eight GCMs are analysed. Ensemble variability in sea ice extent is greater in the mid-Pliocene summer, when half of the models simulate sea-ice-free conditions. Weaker correlations are seen between sea ice extent and temperatures in the pre-industrial era compared to the mid-Pliocene. The need for more comprehensive sea ice proxy data is highlighted, in order to better compare model performances.

Description: Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium François Klein, Hugues Goosse, Nicholas E. Graham, and Dirk Verschuren Clim. Past, 12, 1499-1518, doi:10.5194/cp-12-1499-2016, 2016 This paper analyses global climate model simulations of long-term East African hydroclimate changes relative to proxy-based reconstructions over the last millennium. No common signal is found between model results and reconstructions as well as among the model time series, which suggests that simulated hydroclimate is mostly driven by internal variability rather than by common external forcing.

Description: A 368-year maximum temperature reconstruction based on tree-ring data in the northwestern Sichuan Plateau (NWSP), China Liangjun Zhu, Yuandong Zhang, Zongshan Li, Binde Guo, and Xiaochun Wang Clim. Past, 12, 1485-1498, doi:10.5194/cp-12-1485-2016, 2016 We present a 368-year late summer maximum temperature reconstruction based on spruce tree rings. It touches on the critical topic of climate reconstruction in the eastern edge of Tibetan Plateau and represents an extension and enhancement of climate records for this area. The Little Ice Age was well represented and 20th century warming was not obvious in this reconstruction. This temperature variation may be affected by global land–sea atmospheric circulation as well as solar and volcanic forcing.

Description: The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction Harry Dowsett, Aisling Dolan, David Rowley, Robert Moucha, Alessandro M. Forte, Jerry X. Mitrovica, Matthew Pound, Ulrich Salzmann, Marci Robinson, Mark Chandler, Kevin Foley, and Alan Haywood Clim. Past, 12, 1519-1538, doi:10.5194/cp-12-1519-2016, 2016 Past intervals in Earth history provide unique windows into conditions much different than those observed today. We investigated the paleoenvironments of a past warm interval (~ 3 million years ago). Our reconstruction includes data sets for surface temperature, vegetation, soils, lakes, ice sheets, topography, and bathymetry. These data are being used along with global climate models to expand our understanding of the climate system and to help us prepare for future changes.

Description: Sea ice-related halogen enrichment at Law Dome, coastal East Antarctica Paul Vallelonga, Niccolo Maffezzoli, Andrew D. Moy, Mark A. J. Curran, Tessa R. Vance, Ross Edwards, Gwyn Hughes, Emily Barker, Gunnar Spreen, Alfonso Saiz-Lopez, J. Pablo Corella, Carlos A. Cuevas, and Andrea Spolaor Clim. Past Discuss., doi:10.5194/cp-2016-74,2016 Manuscript under review for CP (discussion: open, 0 comments) We present a study of bromine, iodine and sodium in an ice core from Law Dome, in coastal East Antarctica. We find that bromine and iodine variability at Law Dome is correlated to changes in the area of sea ice along the Law Dome coast as observed by satellite since the early 1970s. These findings are in agreement with a previous study based on MSA and confirm a long-trem trend of sea ice decrease for this sector of Antarctica over the 20th century.

Description: Atmospheric methane control mechanisms during the early Holocene Ji-Woong Yang, Jinho Ahn, Edward J. Brook, and Yeongjun Ryu Clim. Past Discuss., doi:10.5194/cp-2016-75,2016 Manuscript under review for CP (discussion: open, 0 comments) The early Holocene climate is chracterized as an interglacial boundary condition without substantial human influence. Here we present a high-resolution CH 4 time series during the early Holocene for investigating a natural control process. The results show that changes in the ITCZ position and Asian summer monsoon intensity were able to induce ~ 20 to 40 ppb CH 4 variability in millennial time scale by changing low latitude emission, while the contribution of boreal sources increased gradually.

Description: Deforestation decreases resistance of simulated Easter Island climate to drought Alexander Lemburg, Martin Claussen, and Felix Ament Clim. Past Discuss., doi:10.5194/cp-2016-68,2016 Manuscript under review for CP (discussion: open, 0 comments) The deforestation of Easter Island several hundred years ago might have influenced its local near-surface climate. With a series of numerical model experiments we investigate the impact of deforestation on precipitation and near-surface climate. We find that a deforested Easter Island appears to be significantly less resistant to drought than a forested island and thus, deforestation has probably exacerbated the effects of past climate drought spells on Easter Island's socio-ecological systems.

Description: Sea level trends in Southeast Asian seas Climate of the Past, 11, 743-750, 2015 Author(s): M. W. Strassburg, B. D. Hamlington, R. R. Leben, P. Manurung, J. Lumban Gaol, B. Nababan, S. Vignudelli, and K.-Y. Kim Southeast Asian seas span the largest archipelago in the global ocean and provide a complex oceanic pathway connecting the Pacific and Indian oceans. The Southeast Asian sea regional sea level trends are some of the highest observed in the modern satellite altimeter record that now spans almost 2 decades. Initial comparisons of global sea level reconstructions find that 17-year sea level trends over the past 60 years exhibit good agreement with decadal variability associated with the Pacific Decadal Oscillation and related fluctuations of trade winds in the region. The Southeast Asian sea region exhibits sea level trends that vary dramatically over the studied time period. This historical variation suggests that the strong regional sea level trends observed during the modern satellite altimeter record will abate as trade winds fluctuate on decadal and longer timescales. Furthermore, after removing the contribution of the Pacific Decadal Oscillation (PDO) to sea level trends in the past 20 years, the rate of sea level rise is greatly reduced in the Southeast Asian sea region. As a result of the influence of the PDO, the Southeast Asian sea regional sea level trends during the 2010s and 2020s are likely to be less than the global mean sea level (GMSL) trend if the observed oscillations in wind forcing and sea level persist. Nevertheless, long-term sea level trends in the Southeast Asian seas will continue to be affected by GMSL rise occurring now and in the future.

Description: Non-linear regime shifts in Holocene Asian monsoon variability: potential impacts on cultural change and migratory patterns Climate of the Past, 11, 709-741, 2015 Author(s): J. F. Donges, R. V. Donner, N. Marwan, S. F. M. Breitenbach, K. Rehfeld, and J. Kurths The Asian monsoon system is an important tipping element in Earth's climate with a large impact on human societies in the past and present. In light of the potentially severe impacts of present and future anthropogenic climate change on Asian hydrology, it is vital to understand the forcing mechanisms of past climatic regime shifts in the Asian monsoon domain. Here we use novel recurrence network analysis techniques for detecting episodes with pronounced non-linear changes in Holocene Asian monsoon dynamics recorded in speleothems from caves distributed throughout the major branches of the Asian monsoon system. A newly developed multi-proxy methodology explicitly considers dating uncertainties with the COPRA (COnstructing Proxy Records from Age models) approach and allows for detection of continental-scale regime shifts in the complexity of monsoon dynamics. Several epochs are characterised by non-linear regime shifts in Asian monsoon variability, including the periods around 8.5–7.9, 5.7–5.0, 4.1–3.7, and 3.0–2.4 ka BP. The timing of these regime shifts is consistent with known episodes of Holocene rapid climate change (RCC) and high-latitude Bond events. Additionally, we observe a previously rarely reported non-linear regime shift around 7.3 ka BP, a timing that matches the typical 1.0–1.5 ky return intervals of Bond events. A detailed review of previously suggested links between Holocene climatic changes in the Asian monsoon domain and the archaeological record indicates that, in addition to previously considered longer-term changes in mean monsoon intensity and other climatic parameters, regime shifts in monsoon complexity might have played an important role as drivers of migration, pronounced cultural changes, and the collapse of ancient human societies.

Description: Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania) Climate of the Past, 11, 751-764, 2015 Author(s): I. Bouimetarhan, L. Dupont, H. Kuhlmann, J. Pätzold, M. Prange, E. Schefuß, and K. Zonneveld In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ~ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

Description: A 2000-year annual record of snow accumulation rates for Law Dome, East Antarctica Climate of the Past, 11, 697-707, 2015 Author(s): J. Roberts, C. Plummer, T. Vance, T. van Ommen, A. Moy, S. Poynter, A. Treverrow, M. Curran, and S. George Accurate high-resolution records of snow accumulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snowfall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the mid-latitudes as well as regional Antarctic snowfall. Here, we extend the length of the Law Dome accumulation record from 750 years to 2035 years, using recent annual layer dating that extends to 22 BCE. Accumulation rates were calculated as the ratio of measured to modelled layer thicknesses, multiplied by the long-term mean accumulation rate. The modelled layer thicknesses were based on a power-law vertical strain rate profile fitted to observed annual layer thickness. The periods 380–442, 727–783 and 1970–2009 CE have above-average snow accumulation rates, while 663–704, 933–975 and 1429–1468 CE were below average, and decadal-scale snow accumulation anomalies were found to be relatively common (74 events in the 2035-year record). The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger-scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to El Niño–Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) frequencies.

Description: The WAIS Divide deep ice core WD2014 chronology – Part 1: Methane synchronization (68–31 ka BP) and the gas age–ice age difference Climate of the Past, 11, 153-173, 2015 Author(s): C. Buizert, K. M. Cuffey, J. P. Severinghaus, D. Baggenstos, T. J. Fudge, E. J. Steig, B. R. Markle, M. Winstrup, R. H. Rhodes, E. J. Brook, T. A. Sowers, G. D. Clow, H. Cheng, R. L. Edwards, M. Sigl, J. R. McConnell, and K. C. Taylor The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WD gas age–ice age difference (Δage) using a combination of firn densification modeling, ice-flow modeling, and a data set of δ 15 N-N 2 , a proxy for past firn column thickness. The largest Δage at WD occurs during the Last Glacial Maximum, and is 525 ± 120 years. Internally consistent solutions can be found only when assuming little to no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WD chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard–Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu Cave speleothem record. The small Δage at WD provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the "bipolar seesaw".

Description: Mode transitions in Northern Hemisphere Glaciation: Co-evolution of millennial and orbital variability in Quaternary climate David A. Hodell and James E.T. Channell Clim. Past Discuss., doi:10.5194/cp-2016-30,2016 Manuscript under review for CP (discussion: open, 0 comments) For the past 2.7 million years the Earth’s climate has switched more than 50 times between a cold glacial and warm interglacial state. We found the trend towards larger ice sheets over the past 2.7 million years was accompanied by changes in the style, frequency and intensity of shorter-term (millennial) variability. We suggest the interaction between millennial climate change and longer-term variations in the Earth's orbit may be important for explaining the patterns of Quaternary climate.

Description: The WAIS Divide deep ice core WD2014 chronology – Part 2: Annual-layer counting (0–31 ka BP) Michael Sigl, Tyler J. Fudge, Mai Winstrup, Jihong Cole-Dai, David Ferris, Joseph R. McConnell, Ken C. Taylor, Kees C. Welten, Thomas E. Woodruff, Florian Adolphi, Marion Bisiaux, Edward J. Brook, Christo Buizert, Marc W. Caffee, Nelia W. Dunbar, Ross Edwards, Lei Geng, Nels Iverson, Bess Koffman, Lawrence Layman, Olivia J. Maselli, Kenneth McGwire, Raimund Muscheler, Kunihiko Nishiizumi, Daniel R. Pasteris, Rachael H. Rhodes, and Todd A. Sowers Clim. Past, 12, 769-786, doi:10.5194/cp-12-769-2016, 2016 Here we present a chronology (WD2014) for the upper part (0–2850 m; 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide ice core, which is based on layer counting of distinctive annual cycles preserved in the elemental, chemical and electrical conductivity records. We validated the chronology by comparing it to independent high-accuracy, absolutely dated chronologies. Given its demonstrated high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere.

Description: Terrigenous material supply to the Peruvian central continental shelf (Pisco, 14° S) during the last 1000 years: paleoclimatic implications Francisco Javier Briceño-Zuluaga, Abdelfettah Sifeddine, Sandrine Caquineau, Jorge Cardich, Renato Salvatteci, Dimitri Gutierrez, Luc Ortlieb, Federico Velazco, Hugues Boucher, and Carine Machado Clim. Past, 12, 787-798, doi:10.5194/cp-12-787-2016, 2016 Comparison between records reveals a coherent match between the meridional displacement of the ITCZ-SPSH system and the regional fluvial and aeolian terrigenous input variability. The aeolian input intensity and the anoxic conditions recorded by marine sediments showed a close link that suggests a common mechanism associated with SPSH displacement. Changes in sediment discharge to the continental shelf are linked to the southward displacement of the ITCZ-SPSH and Walker circulation.

Description: Solar modulation of flood frequency in central Europe during spring and summer on interannual to multi-centennial timescales Markus Czymzik, Raimund Muscheler, and Achim Brauer Clim. Past, 12, 799-805, doi:10.5194/cp-12-799-2016, 2016 Integrating discharge data of the River Ammer back to 1926 and a 5500-year flood layer record from an annually laminated sediment core of the downstream Ammersee allowed investigating changes in the frequency of major floods in Central Europe on interannual to multi-centennial timescales. Significant correlations between flood frequency variations in both archives and changes in the activity of the Sun suggest a solar influence on the frequency of these hydrometeorological extremes.

Description: Constraints on ocean circulation at the Paleocene–Eocene Thermal Maximum from neodymium isotopes April N. Abbott, Brian A. Haley, Aradhna K. Tripati, and Martin Frank Clim. Past, 12, 837-847, doi:10.5194/cp-12-837-2016, 2016 The Paleocene-Eocene Thermal Maximum (PETM) was a brief period when the Earth was in an extreme greenhouse state. We use neodymium isotopes to suggest that during this time deep-ocean circulation was distinct in each basin (North and South Atlanic, Southern, Pacific) with little exchange between. Moreover, the Pacific data show the most variability, suggesting this was a critical region possibly involved in both PETM triggering and remediation.

Description: The climate reconstruction in Shandong Peninsula, northern China, during the last millennium based on stalagmite laminae together with a comparison to δ 18 O Qing Wang, Houyun Zhou, Ke Cheng, Hong Chi, Chuan-Chou Shen, Changshan Wang, and Qianqian Ma Clim. Past, 12, 871-881, doi:10.5194/cp-12-871-2016, 2016 The upper part of stalagmite ky1 (from top to 42.769 mm depth), consisting of 678 laminae, was collected from a cave in northern China, located in the East Asia monsoon area. The time of deposition ranges from AD 1217±20 to 1894±20. The analysis shows that both the variations in the thickness of the laminae themselves and the fluctuating degree of variation in the thickness of the laminae of stalagmite ky1 have obviously staged characteristics and synchronized with climate.

Description: Palaeo-sea-level and palaeo-ice-sheet databases: problems, strategies, and perspectives André Düsterhus, Alessio Rovere, Anders E. Carlson, Benjamin P. Horton, Volker Klemann, Lev Tarasov, Natasha L. M. Barlow, Tom Bradwell, Jorie Clark, Andrea Dutton, W. Roland Gehrels, Fiona D. Hibbert, Marc P. Hijma, Nicole Khan, Robert E. Kopp, Dorit Sivan, and Torbjörn E. Törnqvist Clim. Past, 12, 911-921, doi:10.5194/cp-12-911-2016, 2016 This review/position paper addresses problems in creating new interdisciplinary databases for palaeo-climatological sea-level and ice-sheet data and gives an overview on new advances to tackle them. The focus therein is to define and explain strategies and highlight their importance to allow further progress in these fields. It also offers important insights into the general problem of designing competitive databases which are also applicable to other communities within the palaeo-environment.

Description: Spring temperature variability over Turkey since 1800 CE reconstructed from a broad network of tree-ring data Nesibe Köse, H. Tuncay Güner, Grant L. Harley, and Joel Guiot Clim. Past Discuss., doi:10.5194/cp-2015-195,2016 Manuscript under review for CP (discussion: open, 0 comments) The 20 th century was marked by significant decreases in spring temperature ranges and increased nighttime temperatures throughout Turkey. The meteorological observational period in Turkey, which starts ca. 1929 CE, is too short for understanding long-term climatic variability. Hence, the historical context of this gradual warming trend in spring temperatures is unclear. Here we use a network of 23 tree-ring chronologies to provide a high-resolution spring (March–April) temperature reconstruction over Turkey during the period 1800–2002. The reconstruction model accounted for 67 % (Adj. R 2 = 0.64, p ≤ 0.0001) of the instrumental temperature variance over the full calibration period (1930–2002). During the pre-instrumental period (1800–1929) we captured more cold events ( n = 23) than warm ( n = 13), and extreme cold and warm events were typically of short duration (1–2 years). Compared to coeval reconstructions of precipitation in the region, our results are similar with durations of extreme wet and dry events. The reconstruction is punctuated by a temperature increase during the 20 th century; yet extreme cold and warm events during the 19 th century seem to eclipse conditions during the 20 th century. During the 19 th century, annual temperature ranges are more volatile and characterized by more short-term fluctuations compared to the 20 th century. During the period 1900–2002, our reconstruction shows a gradual warming trend, which includes the period during which diurnal temperature ranges decreased as a result of increased urbanization in Turkey.

Description: Optimal site selection for a high-resolution ice core record in East Antarctica Tessa R. Vance, Jason L. Roberts, Andrew D. Moy, Mark A. J. Curran, Carly R. Tozer, Ailie J. E. Gallant, Nerilie J. Abram, Tas D. van Ommen, Duncan A. Young, Cyril Grima, Don D. Blankenship, and Martin J. Siegert Clim. Past, 12, 595-610, doi:10.5194/cp-12-595-2016, 2016 This study details a systematic approach to finding a new high-resolution East Antarctic ice core site. The study initially outlines seven criteria that a new site must fulfil, encompassing specific accumulation, ice dynamics and atmospheric circulation aspects. We then use numerous techniques including Antarctic surface mass balance syntheses, ground-truthing of satellite data by airborne radar surveys and reanalysis products to pinpoint promising regions.

Description: Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores Lucie Bazin, Amaelle Landais, Emilie Capron, Valérie Masson-Delmotte, Catherine Ritz, Ghislain Picard, Jean Jouzel, Marie Dumont, Markus Leuenberger, and Frédéric Prié Clim. Past, 12, 729-748, doi:10.5194/cp-12-729-2016, 2016 We present new measurements of δ O 2 ⁄N 2 and δ 18 O atm performed on well-conserved ice from EDC covering MIS5 and between 380 and 800 ka. The combination of the observation of a 100 ka periodicity in the new δ O 2 ⁄N 2 record with a MIS5 multi-site multi-proxy study has revealed a potential influence of local climatic parameters on δ O 2 ⁄N 2 . Moreover, we propose that the varying delay between d18Oatm and precession for the last 800 ka is affected by the occurrence of ice sheet discharge events.

Description: Paleoclimate in continental northwestern Europe during the Eemian and Early-Weichselian (125–97 ka): insights from a Belgian speleothem Stef Vansteenberge, Sophie Verheyden, Hai Cheng, Lawrence R. Edwards, Eddy Keppens, and Philippe Claeys Clim. Past Discuss., doi:10.5194/cp-2016-15,2016 Manuscript under review for CP (discussion: open, 0 comments) The use of stalagmites for Last Interglacial continental climate reconstructions in Europe has been successful in the past, however to expand the geographical coverage additional data from Belgium is presented. It has been shown that stalagmite growth, morphology and stable isotope content reflect regional and local climate conditions, with Eemian optimum climate occurring between 125.3 and 117.3 ka. The start the Weichselian is expressed by a stop of growth caused by a drying climate.

Description: Extreme flood events reconstruction during the last century in the El Bibane lagoon (Southeast of Tunisia): A Multi-proxy Approach A. Affouri, L. Dezileau, and N. Kallel Clim. Past Discuss., doi:10.5194/cp-2016-40,2016 Manuscript under review for CP (discussion: open, 0 comments) The past flood activity was investigated using a sedimentological and geochemical analysis of surfaces sediments from the Southeast of Tunisia catchment in order to trace the origin of sediments deposit in the El Bibane lagoon. Aeolian, fluvial and marine source. This multi-proxy analysis on the BL12-10 core shows that finer material, high content of clay and silt, and high content of the elemental ratio Fe/Ca and Ti/Ca characterize the sedimentological signature of paleoflood levels.

Description: Model simulations of early westward flow across the Tasman Gateway during the early Eocene Willem P. Sijp, Anna S. von der Heydt, and Peter K. Bijl Clim. Past, 12, 807-817, doi:10.5194/cp-12-807-2016, 2016 The timing and role in ocean circulation and climate of the opening of Southern Ocean gateways is as yet elusive. Here, we present the first model results specific to the early-to-middle Eocene where, in agreement with the field evidence, a southerly shallow opening of the Tasman Gateway does indeed cause a westward flow across the Tasman Gateway, in agreement with recent micropalaeontological studies.

Description: Chemical composition of soluble and insoluble particles around the last termination preserved in the Dome C ice core, inland Antarctica Ikumi Oyabu, Yoshinori Iizuka, Eric Wolff, and Margareta Hansson Clim. Past Discuss., doi:10.5194/cp-2016-42,2016 Manuscript under review for CP (discussion: open, 0 comments) This study presented the chemical compositions of non-volatile particles around the last termination in the Dome C ice core by using the sublimation-EDS method. The major soluble salt particles are CaSO4, Na 2 SO 4 , and NaCl, and time-series changes in the composition of these salts are similar to those for the Dome Fuji ice core. However, some differences occurred. The sulfatization rate of NaCl at Dome C is higher than that at Dome Fuji.

Description: Revisiting carbonate chemistry controls on planktic foraminifera Mg /  Ca: implications for sea surface temperature and hydrology shifts over the Paleocene–Eocene Thermal Maximum and Eocene–Oligocene transition David Evans, Bridget S. Wade, Michael Henehan, Jonathan Erez, and Wolfgang Müller Clim. Past, 12, 819-835, doi:10.5194/cp-12-819-2016, 2016 We show that seawater pH exerts a substantial control on planktic foraminifera Mg / Ca, a widely applied palaeothermometer. As a result, temperature reconstructions based on this proxy are likely inaccurate over climatic events associated with a significant change in pH. We examine the implications of our findings for hydrological and temperature shifts over the Paleocene-Eocene Thermal Maximum and for the degree of surface ocean precursor cooling before the Eocene-Oligocene transition.

Description: Sea surface temperature variability in the central-western Mediterranean Sea during the last 2700 years: a multi-proxy and multi-record approach Mercè Cisneros, Isabel Cacho, Jaime Frigola, Miquel Canals, Pere Masqué, Belen Martrat, Marta Casado, Joan O. Grimalt, Leopoldo D. Pena, Giulia Margaritelli, and Fabrizio Lirer Clim. Past, 12, 849-869, doi:10.5194/cp-12-849-2016, 2016 We present a high-resolution multi-proxy study about the evolution of sea surface conditions along the last 2700 yr in the north-western Mediterranean Sea based on five sediment records from two different sites north of Minorca. The novelty of the results and the followed approach, constructing stack records from the studied proxies to preserve the most robust patterns, provides a special value to the study. This complex period appears to have significant regional changes in the climatic signal.

Description: 〈b〉Influence of radiative forcing factors on ground–air temperature coupling during the last millennium: implications for borehole climatology〈/b〉〈br〉 Camilo Melo-Aguilar, J. Fidel González-Rouco, Elena García-Bustamante, Jorge Navarro-Montesinos, and Norman Steinert〈br〉 Clim. Past, 14, 1583-1606, https://doi.org/10.5194/cp-14-1583-2018, 2018〈br〉 Air–ground temperature coupling is the central assumption of borehole temperature reconstructions. Here, this premise is assessed from a pseudo-reality perspective by considering last millennium ensembles of simulations from the Community Earth System Model. The results show that long-term variations in the energy fluxes at the surface during industrial times, due to the influence of external forcings, impact the long-term air–ground temperature coupling.

Description: 〈b〉Effect of high dust amount on surface temperature during the Last Glacial Maximum: a modelling study using MIROC-ESM〈/b〉〈br〉 Rumi Ohgaito, Ayako Abe-Ouchi, Ryouta O'ishi, Toshihiko Takemura, Akinori Ito, Tomohiro Hajima, Shingo Watanabe, and Michio Kawamiya〈br〉 Clim. Past, 14, 1565-1581, https://doi.org/10.5194/cp-14-1565-2018, 2018〈br〉 The behaviour of dust in terms of climate can be investigated using past climate. The Last Glacial Maximum (LGM; 21000 years before present) is known to be dustier. We investigated the impact of plausible dust distribution on the climate of the LGM using an Earth system model and found that the higher dust load results in less cooling over the polar regions. The main finding is that radiative perturbation by the high dust loading does not necessarily cool the surface surrounding Antarctica.

Description: 〈b〉The 4.2 ka BP Event in the Mediterranean Region: an overview〈/b〉〈br〉 Monica Bini, Giovanni Zanchetta, Aurel Persoiu, Rosine Cartier, Albert Català, Isabel Cacho, Jonathan R. Dean, Federico Di Rita, Russell N. Drysdale, Martin Finnè, Ilaria Isola, Bassem Jalali, Fabrizio Lirer, Donatella Magri, Alessia Masi, Leszek Marks, Anna Maria Mercuri, Odile Peyron, Laura Sadori, Marie-Alexandrine Sicre, Fabian Welc, Christoph Zielhofer, and Elodie Brisset〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-147,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 2 comments)〈br〉 The Mediterranean region has returned some of the clearest evidence of a climatically dry period occurring at ca. 4200 years ago. We reviewed selected proxies to infer regional climate patterns between 4.3 and 3.8 cal ka BP. Temperature data suggest a cooling anomaly, even if this is not uniform, whereas winter was drier along with dry summers. However, some exceptions to this prevail, where wetter condition seems to have persisted, suggesting regional heterogeneity.

Description: 〈b〉Varying regional δ〈sup〉18〈/sup〉O–temperature relationship in high resolution stable water isotopes from East Greenland〈/b〉〈br〉 Christian Holme, Vasileios Gkinis, Mika Lanzky, Valerie Morris, Martin Olesen, Abigail Thayer, Bruce H. Vaughn, and Bo M. Vinther〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-169,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 This study investigates the linear relationship between the water isotopes of three East Greenland ice cores and regional temperatures. By comparing the water isotopes with nearby instrumental temperature records and reanalysis data, this study demonstrates that it can be problematic to reconstruct temperatures through regression of water isotope data from coastal ice cores. We further show that the varying linear relationship could be connected with changes in sea ice near the drill site.

Description: 〈b〉Simulating the Climate Response to Atmospheric Oxygen Variability in the Phanerozoic〈/b〉〈br〉 David C. Wade, Nathan Luke Abraham, Alexander Farnsworth, Paul J. Valdes, Fran Bragg, and Alexander T. Archibald〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-149,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 The amount of O〈sub〉2〈/sub〉 in the atmosphere may have varied from as little as 10 % to as high as 35 % during the last 541 Ma. These changes are large enough to have lead to changes in atmospheric mass, which may alter the radiative budget of the atmosphere. Here we present the first fully 3D numerical model simulations to investigate the climate impacts of changes in O〈sub〉2〈/sub〉 during different climate states. We identify a complex new mechanism causing increases in surface temperature when O〈sub〉2〈/sub〉 levels were higher.

Description: 〈b〉Identifying teleconnections and multidecadal variability of East Asian surface temperature during the last millennium in CMIP5 simulations〈/b〉〈br〉 Satyaban B. Ratna, Timothy J. Osborn, Manoj Joshi, Bao Yang, and Jianglin Wang〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-164,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 We examine the relationships in models and reconstructions between multidecadal variability of East Asian temperature and two extratropical modes of variability. The relationship between East Asian temperature and Pacific multidecadal variability is largely driven by internal variability, whereas with Atlantic multidecadal variability it is more strongly influenced by the presence or absence of external forcing. We discuss the implications for diagnosing teleconnections from reconstructions.

Description: 〈b〉Hydro-climatic variability in the southwestern Indian Ocean between 6000 and 3000 years ago〈/b〉〈br〉 Hanying Li, Hai Cheng, Ashish Sinha, Gayatri Kathayat, Christoph Spötl, Aurèle Anquetil André, Arnaud Meunier, Jayant Biswas, Pengzhen Duan, Youfeng Ning, and Richard Lawrence Edwards〈br〉 Clim. Past, 14, 1881-1891, https://doi.org/10.5194/cp-14-1881-2018, 2018〈br〉 The 〈q〉4.2 ka event〈/q〉 between 4.2 and 3.9 ka has been widely discussed in the Northern Hemsiphere but less reported in the Southern Hemisphere. Here, we use speleothem records from Rodrigues in the southwestern Indian Ocean spanning from 6000 to 3000 years ago to investigate the regional hydro-climatic variability. Our records show no evidence for an unusual climate anomaly between 4.2 and 3.9 ka. Instead, it shows a multi-centennial drought between 3.9 and 3.5 ka.

Description: 〈b〉Late Miocene to Recent High Resolution Eastern Equatorial Pacific Carbonate Records: Stratigraphy linked by dissolution and paleoproductivity〈/b〉〈br〉 Mitchell Lyle, Anna Joy Drury, Jun Tian, Roy Wilkens, and Thomas Westerhold〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-157,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 Ocean sediment records document changes in Earth's carbon cycle and ocean productivity. We present 8 Myr CaCO〈sub〉3〈/sub〉 and bulk sediment records matched from 7 eastern Pacific scientific drill sites to identify intervals of excess CaCO〈sub〉3〈/sub〉 dissolution (high carbon storage in the oceans) and excess burial of plankton hard parts indicating high productivity. We define the regional extent of production intervals and explore the impact of the closure of the Atlantic-Pacific Panama connection on CaCO〈sub〉3〈/sub〉 burial.

Description: 〈b〉Equilibrium simulations of Marine Isotope Stage 3 climate〈/b〉〈br〉 Chuncheng Guo, Kerim H. Nisancioglu, Mats Bentsen, Ingo Bethke, and Zhongshi Zhang〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-165,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 We present an equilibrium simulation of the climate of Marine Isotope Stage 3, with an IPCC-class model with a relatively high model resolution and a long integration. The simulated climate resembles a warm interstadial state, as indicated by reconstructions of Greenland temperature, sea ice extent, and AMOC. Sensitivity experiments to changes in atmospheric CO〈sub〉2〈/sub〉 levels and ice sheet size show that the model is in a relatively stable climate state without multiple equilibria.

Description: 〈b〉Evaluating the timing and structure of the 4.2 ka event in the Indian summer monsoon domain from an annually resolved speleothem record from Northeast India〈/b〉〈br〉 Gayatri Kathayat, Hai Cheng, Ashish Sinha, Max Berkelhammer, Haiwei Zhang, Pengzhen Duan, Hanying Li, Xianglei Li, Youfeng Ning, and R. Lawrence Edwards〈br〉 Clim. Past, 14, 1869-1879, https://doi.org/10.5194/cp-14-1869-2018, 2018〈br〉 The 4.2 ka event is generally characterized as an approximately 300-year period of major global climate anomaly. However, the climatic manifestation of this event remains unclear in the Indian monsoon domain. Our high-resolution and precisely dated speleothem record from Meghalaya, India, characterizes the event as consisting of a series of multi-decadal droughts between 3.9 and 4.0 ka rather than a singular pulse of multi-centennial drought as previously thought.

Description: 〈b〉Sedproxy: a forward model for sediment-archived climate proxies〈/b〉〈br〉 Andrew M. Dolman and Thomas Laepple〈br〉 Clim. Past, 14, 1851-1868, https://doi.org/10.5194/cp-14-1851-2018, 2018〈br〉 Climate proxies from marine sediments provide an important record of past temperatures, but contain noise from many sources. These include mixing by burrowing organisms, seasonal and habitat biases, measurement error, and small sample size effects. We have created a forward model that simulates the creation of proxy records and provides it as a user-friendly R package. It allows multiple sources of uncertainty to be considered together when interpreting proxy climate records.

Description: 〈b〉Holocene hydrography evolution in the Alboran Sea: a multi-record and multiproxy comparison〈/b〉〈br〉 Albert Català, Isabel Cacho, Jaime Frigola, Leopoldo D. Pena, and Fabrizio Lirer〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-163,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 We present a new high-resolution sea surface temperature (SST) reconstruction for the Holocene (last 11 700 years) in the westernmost Mediterranean See. We identify that the Holocene describes three sub-periods. Early-Holocene with warmest SST, the Middle-Holocene with a cooling trend ending at 4200 years which is identified as a double peak cooling event that marks the transition between the Middle and Late Holocene with very different behaviour in both long and short term SST variability.

Description: 〈b〉Long-term deglacial permafrost carbon dynamics in MPI-ESM〈/b〉〈br〉 Thomas Schneider von Deimling, Thomas Kleinen, Gustaf Hugelius, Christian Knoblauch, Christian Beer, and Victor Brovkin〈br〉 Clim. Past, 14, 2011-2036, https://doi.org/10.5194/cp-14-2011-2018, 2018〈br〉 Past cold ice age temperatures and the subsequent warming towards the Holocene had large consequences for soil organic carbon (SOC) stored in perennially frozen grounds. Using an Earth system model we show how the spread in areas affected by permafrost have changed under deglacial warming, along with changes in SOC accumulation. Our model simulations suggest phases of circum-Arctic permafrost SOC gain and losses, with a net increase in SOC between the last glacial maximum and the pre-industrial.

Description: 〈b〉Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective from Kane Basin〈/b〉〈br〉 Eleanor Georgiadis, Jacques Giraudeau, Philippe Martinez, Patrick Lajeunesse, Guillaume St-Onge, Sabine Schmidt, and Guillaume Massé〈br〉 Clim. Past, 14, 1991-2010, https://doi.org/10.5194/cp-14-1991-2018, 2018〈br〉 We present our results from a radiocarbon-dated core collected in central Nares Strait, NW Greenland. Sedimentological and geochemical data reveal that marine sedimentation began ca. 9.0 cal ka BP with the complete opening of the strait occurring at 8.3 cal ka BP. The collapse of the glacial buttress in central Nares Strait led to accelerated glacial fluxes of the bordering ice sheets between 8.3 and 7.5 cal ka BP, while the Humboldt Glacier retreated in eastern Kane Basin ca. 8.1 cal ka BP.

Description: 〈b〉The relevance of mid-Holocene Arctic warming to the future〈/b〉〈br〉 Masakazu Yoshimori and Marina Suzuki〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-175,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 1 comment)〈br〉 A relation between the mid-Holocene (MH) and future Arctic warming mechanism is investigated with focus on the similarities of physical processes. The several key processes are identified which are linked to both multi-model mean response and multi-model variation of the response. This study indicates that the models are required to simulate the MH Arctic climate well to provide more confidence to the future Arctic climate projections.

Description: 〈b〉Decadal-scale progression of Dansgaard-Oeschger warming events〈/b〉〈br〉 Tobias Erhardt, Emilie Capron, Sune Olander Rasmussen, Simon Schüpbach, Matthias Bigler, Florian Adolphi, and Hubertus Fischer〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-176,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 The cause of the rapid warming events documented in proxy records across the Northern Hemisphere during the last glacial has been a long-standing puzzle in paleo-climate research. Here we use high resolution ice core data from to cores in Greenland to investigate the progression during the onset of these events on muti-annual time scales to test their plausible triggers. We show that atmospheric circulation changes preceded the warming in Greenland and the collapse of the sea ice by a decade.

Description: 〈b〉A large increase in the carbon inventory of the land biosphere since the Last Glacial Maximum: constraints from multi-proxy data〈/b〉〈br〉 Aurich Jeltsch-Thömmes, Gianna Battaglia, Olivier Cartapanis, Samuel L. Jaccard, and Fortunat Joos〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-167,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 A long standing question in climate science is concerned with which processes contributed to the increase in atmospheric CO〈sub〉2〈/sub〉 after the last ice age. From the range of possible processes we try to constrain the change in carbon storage in the land biosphere. By combining ice-core and marine sediment data in a modeling framework we show that the carbon storage in the land biosphere increased largely after the last ice age. This will help to further understand processes at work in the Earth system.

Description: 〈b〉Climate evolution across the Mid-Brunhes Transition〈/b〉〈br〉 Aaron M. Barth, Peter U. Clark, Nicholas S. Bill, Feng He, and Nicklas G. Pisias〈br〉 Clim. Past, 14, 2071-2087, https://doi.org/10.5194/cp-14-2071-2018, 2018〈br〉 Multiple components of the global climate system record a transition ~ 430 ka from lower- to higher-amplitude glacial cycles. Statistical analyses of globally distributed climate proxies show that a sequence of events including persistent Asian summer monsoons, weak glaciation, and reorganization of water masses preceded the transition to higher interglacial values for temperature, atmospheric greenhouse gases, and sea level.

Description: 〈b〉Understanding the Australian Monsoon change during the Last Glacial Maximum with a multi-model ensemble〈/b〉〈br〉 Mi Yan, Bin Wang, Jian Liu, Axing Zhu, Liang Ning, and Jian Cao〈br〉 Clim. Past, 14, 2037-2052, https://doi.org/10.5194/cp-14-2037-2018, 2018〈br〉 〈p〉The response of the Australian monsoon to external forcings and related mechanisms during the Last Glacial Maximum (LGM) are investigated by multi-model experiments in CMIP5–PMIP3. Although the annual mean precipitation over the Australian monsoon region decreases, the annual range, or the monsoonality, is enhanced. The precipitation increases in early austral summer and decreases in austral winter, resulting in the amplified annual range, but the main contribution comes from the decreased precipitation in austral winter. The decreased winter precipitation is primarily caused by weakened upward motion, although reduced water vapor also has a moderate contribution. The weakened upward motion is induced by the enhanced land–sea thermal contrast, which intensifies the divergence over northern Australia. The increased Australian monsoon rainfall in early summer, however, is an integrated result of the positive effect of local dynamic processes (enhanced moisture convergence) and the negative effect of thermodynamics (reduced moisture content). The enhanced moisture convergence is caused by two factors: the strengthened northwest–southeast thermal contrast between the cooler Indochina–western Indonesia and the warmer northeastern Australia, and the east–west sea surface temperature gradients between the warmer western Pacific and cooler eastern Indian Ocean, both due to the alteration of land–sea configuration arising from the sea level drop. The enhanced Australian monsoonality in the LGM is not associated with global-scale circulation change such as the shift of the Intertropical Convergence Zone; rather, it is mainly due to the change of regional circulations around Australia arising from the changes in land–sea contrast and the east–west SST gradients over the Indian and western Pacific oceans. This finding should be taken into account when investigating its future change under global warming. Our findings may also explain why proxy records indicate different changes in Australian monsoon precipitation during the LGM.〈/p〉

Description: 〈b〉What climate signal is contained in decadal- to centennial-scale isotope variations from Antarctic ice cores?〈/b〉〈br〉 Thomas Münch and Thomas Laepple〈br〉 Clim. Past, 14, 2053-2070, https://doi.org/10.5194/cp-14-2053-2018, 2018〈br〉 Proxy data on climate variations contain noise from many sources and, for reliable estimates, we need to determine those temporal scales at which the climate signal in the proxy record dominates the noise. We developed a method to derive timescale-dependent estimates of temperature proxy signal-to-noise ratios, which we apply and discuss in the context of Antarctic ice-core records but which in general are applicable to a large set of palaeoclimate records.

Description: 〈b〉Impact of different estimations of the background-error covariance matrix on climate reconstructions based on data assimilation〈/b〉〈br〉 Veronika Valler, Jörg Franke, and Stefan Brönnimann〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-168,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 In recent years, the data assimilation approach was adapted to the field of paleoclimatology to reconstruct past climate fields by combining model simulations and observations. To improve the performance of our paleo data assimilation system, we tested various techniques that are well established in weather forecasting, and evaluated their impact on assimilating instrumental data and proxy records (tree rings).

Description: 〈b〉The climate of Granada (southern Spain) during the first third of the 18th century (1706–1730) according to documentary sources〈/b〉〈br〉 Fernando S. Rodrigo〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-170,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 Climate of Granada (southern Spain) during the first third of the 18th century is reconstructed. Results suggest that climatic conditions were similar to those of the first decades of the 20th century, when the global warming signal was of less importance than today. In addition, the manuscript presents the instrumental data taken in Granada the year 1729, probably the first instrumental meteorological data recorded in Spain. Some extreme events, as the cold wave of the winter 1729, are studied.

Description: Multiscale monsoon variability during the last two climatic cycles revealed by spectral signals in Chinese loess and speleothem records Climate of the Past, 11, 1067-1075, 2015 Author(s): Y. Li, N. Su, L. Liang, L. Ma, Y. Yan, and Y. Sun The East Asian Monsoon (EAM) exhibits a significant variability on timescales ranging from tectonic to centennial as inferred from loess, speleothem and marine records. However, the relative contributions and plausible driving forces of the monsoon variability at different timescales remain controversial. Here, we spectrally explore time series of loess grain size and speleothem δ 18 O records and decompose the two proxies into intrinsic components using the empirical mode decomposition method. Spectral results of these two proxies display clear glacial and orbital periodicities corresponding to ice volume and solar cycles, and evident millennial signals which are in pace with Heinrich rhythm and Dansgaard–Oeschger (DO) cycles. Five intrinsic components are parsed out from loess grain size and six intrinsic components from speleothem δ 18 O records. Combined signals are correlated further with possible driving factors including the ice volume, insolation and North Atlantic cooling from a linear point of view. The relative contributions of components differ significantly between loess grain size and speleothem δ 18 O records. Coexistence of glacial and orbital components in the loess grain size implies that both ice volume and insolation have distinctive impacts on the winter monsoon variability, in contrast to the predominant precessional impact on the speleothem δ 18 O variability. Moreover, the millennial components are evident in loess grain size and speleothem δ 18 O records with variances of 13 and 17 %, respectively. A comparison of the millennial-scale signals of these two proxies reveals that abrupt changes in the winter and summer monsoons over the last 260 kyr share common features and similar driving forces linked to high-latitude Northern Hemisphere climate.

Description: Obliquity forcing of low-latitude climate Climate of the Past, 11, 1335-1346, 2015 Author(s): J. H. C. Bosmans, F. J. Hilgen, E. Tuenter, and L. J. Lourens The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

Description: Palaeo plant diversity in subtropical Africa – ecological assessment of a conceptual model of climate–vegetation interaction Climate of the Past, 11, 1361-1374, 2015 Author(s): V. P. Groner, M. Claussen, and C. Reick We critically reassess a conceptual model here, dealing with the potential effect of plant diversity on climate–vegetation feedback, and we provide an improved version adjusted to plant types that prevailed during the African Humid Period (AHP). Our work contributes to the understanding of the timing and abruptness of vegetation decline at the end of the AHP, investigated by various working groups during the past 2 decades using a wide range of model and palaeo-proxy reconstruction approaches. While some studies indicated an abrupt collapse of vegetation at the end of the AHP, others suggested a gradual decline. Claussen et al. (2013) introduced a new aspect in the discussion, proposing that plant diversity in terms of moisture requirements could affect the strength of climate–vegetation feedback. In a conceptual model study, the authors illustrated that high plant diversity could stabilize an ecosystem, whereas a reduction in plant diversity might allow for an abrupt regime shift under gradually changing environmental conditions. In the light of recently published pollen data and the current state of ecological literature, the conceptual model by Claussen et al. (2013) reproduces the main features of different plant types interacting together with climate, but it does not capture the reconstructed diversity of AHP vegetation. Especially tropical gallery forest taxa, indirectly linked to local precipitation, are not appropriately represented. With a new model version adjusted to AHP vegetation, we can simulate a diverse mosaic-like environment as reconstructed from pollen, and we observe a stabilizing effect of high functional diversity on vegetation cover and precipitation. Sensitivity studies with different combinations of plant types highlight the importance of plant composition on system stability, and the stabilizing or destabilizing potential a single plant type may inherit. The model's simplicity limits its application; however, it provides a useful tool to study the roles of real plant types in an ecosystem and their combined climate–vegetation feedback under changing precipitation regimes.

Description: Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr Climate of the Past, 11, 1395-1416, 2015 Author(s): S. Fujita, F. Parrenin, M. Severi, H. Motoyama, and E. W. Wolff Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O 2 / N 2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O 2 / N 2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δ D ice , at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

Description: Increased aridity in southwestern Africa during the warmest periods of the last interglacial Climate of the Past, 11, 1417-1431, 2015 Author(s): D. H. Urrego, M. F. Sánchez Goñi, A.-L. Daniau, S. Lechevrel, and V. Hanquiez Terrestrial and marine climatic tracers from marine core MD96-2098 were used to reconstruct glacial–interglacial climate variability in southwestern Africa between 194 and 24 thousand years before present. The pollen record documented three pronounced expansions of Nama-karoo and fine-leaved savanna during the last interglacial (Marine Isotopic Stage 5 – MIS 5). These Nama-karoo and fine-leaved savanna expansions were linked to increased aridity during the three warmest substadials of MIS 5. Enhanced aridity potentially resulted from a combination of reduced Benguela Upwelling, expanded subtropical high-pressure cells, and reduced austral-summer precipitation due to a northward shift of the Intertropical Convergence Zone. Decreased austral-winter precipitation was likely linked to a southern displacement of the westerlies. In contrast, during glacial isotopic stages MIS 6, 4 and 3, fynbos expanded at the expense of Nama-karoo and fine-leaved savanna indicating a relative increase in precipitation probably concentrated during the austral winter months. Our record also suggested that warm–cold or cold–warm transitions between isotopic stages and substages were punctuated by short increases in humidity. Increased aridity during MIS 5e, 5c and 5a warm substages coincided with minima in both precessional index and global ice volume. On the other hand, austral-winter precipitation increases were associated with precession maxima at the time of well-developed Northern Hemisphere ice caps.

Description: Late Weichselian and Holocene palaeoceanography of Storfjordrenna, southern Svalbard Climate of the Past, 11, 587-603, 2015 Author(s): M. Łącka, M. Zajączkowski, M. Forwick, and W. Szczuciński Multiproxy analyses (including benthic and planktonic foraminifera, δ 18 O and δ 13 C records, grain-size distribution, ice-rafted debris, XRF geochemistry and magnetic susceptibility) were performed on a 14 C-dated marine sediment core from Storfjordrenna, located off of southern Svalbard. The sediments in the core cover the termination of Bølling–Allerød, the Younger Dryas and the Holocene and reflect general changes in the oceanography/climate of the European Arctic after the last glaciation. Grounded ice of the last Svalbard–Barents Sea Ice Sheet retreated from the coring site ca. 13 950 cal yr BP. During the transition from the subglacial to glaciomarine setting, Arctic Waters dominated the hydrography in Storfjordrenna. However, the waters were not uniformly cold and experienced several warmer spells. A progressive warming and marked change in the nature of the hydrology occurred during the early Holocene. Relatively warm and saline Atlantic Water began to dominate the hydrography starting from approximately 9600 cal yr BP. Although the climate in eastern Svalbard was milder at that time than at present (smaller glaciers), two periods of slight cooling were observed in 9000–8000 and 6000–5500 cal yr BP. A change in the Storfjordrenna oceanography occurred at the beginning of the late Holocene (i.e. 3600 cal yr BP) synchronously with glacier growth on land and enhanced bottom current velocities. Although cooling was observed in the Surface Water, Atlantic Water remained present in the deeper portion of the water column of Storfjordrenna.

Description: Diminished greenhouse warming from Archean methane due to solar absorption lines Climate of the Past, 11, 559-570, 2015 Author(s): B. Byrne and C. Goldblatt Previous research has shown that methane may have been sustained at high concentrations in the Archean atmosphere, helping to offset lower insolation and solve the faint young sun problem. However, recent updates to the HITRAN (High-Resolution Transmission) line database have significantly increased the shortwave absorption by CH 4 in comparison to older versions of the database (e.g. HITRAN 2000). Here we investigate the climatological implications of strong shortwave CH 4 absorption in an Archean atmosphere rich in CH 4 . We show that the surface warming at CH 4 abundances 〉10 -3 is diminished relative to the HITRAN 2000 line data. Strong shortwave absorption also results in a~warm stratosphere and lower tropopause. We discuss these results in the context of contemporary research on the Archean climate and how these results could affect the formation of stratospheric clouds and an organic haze.

Description: Interannual climate variability seen in the Pliocene Model Intercomparison Project Climate of the Past, 11, 605-618, 2015 Author(s): C. M. Brierley Following reconstructions suggesting weakened temperature gradients along the Equator in the early Pliocene, there has been much speculation about Pliocene climate variability. A major advance for our knowledge about the later Pliocene has been the coordination of modelling efforts through the Pliocene Model Intercomparison Project (PlioMIP). Here the changes in interannual modes of sea surface temperature variability will be presented across PlioMIP. Previously, model ensembles have shown little consensus in the response of the El Niño–Southern Oscillation (ENSO) to imposed forcings – either for the past or future. The PlioMIP ensemble, however, shows surprising agreement, with eight models simulating reduced variability and only one model indicating no change. The Pliocene's robustly weaker ENSO also saw a shift to lower frequencies. Model ensembles focussed on a wide variety of forcing scenarios have not yet shown this level of coherency. Nonetheless, the PlioMIP ensemble does not show a robust response of either ENSO flavour or sea surface temperature variability in the tropical Indian and North Pacific oceans. Existing suggestions linking ENSO properties to to changes in zonal temperature gradient, seasonal cycle and the elevation of the Andes Mountains are investigated, yet prove insufficient to explain the consistent response. The reason for this surprisingly coherent signal warrants further investigation.

Description: The impact of Sahara desertification on Arctic cooling during the Holocene Climate of the Past, 11, 571-586, 2015 Author(s): F. J. Davies, H. Renssen, M. Blaschek, and F. Muschitiello Since the start of the Holocene, temperatures in the Arctic have steadily declined. This has been accredited to the orbitally forced decrease in summer insolation reconstructed over the same period. However, here we present climate modelling results from an Earth model of intermediate complexity (EMIC) that indicate that 17–40% of the cooling in the Arctic, over the period 9–0 ka, was a direct result of the desertification that occurred in the Sahara after the termination of the African Humid Period. We have performed a suite of sensitivity experiments to analyse the impact of different combinations of forcings, including various vegetation covers in the Sahara. Our simulations suggest that over the course of the Holocene, a strong increase in surface albedo in the Sahara as a result of desertification led to a regional increase in surface pressure, a weakening of the trade winds, the westerlies and the polar easterlies, which in turn reduced the meridional heat transported by the atmosphere to the Arctic. We conclude that during interglacials, the climate of the Northern Hemisphere is sensitive to changes in Sahara vegetation type.

Description: Inferring palaeo-accumulation records from ice-core data by an adjoint-based method: application to James Ross Island's ice core Climate of the Past, 11, 547-557, 2015 Author(s): C. Martín, R. Mulvaney, G. H. Gudmundsson, and H. Corr Ice cores contain a record of snow precipitation that includes information about past atmospheric circulation and mass imbalance in the polar regions. We present a novel approach to reconstruct a climatic record – by both optimally dating an ice core and deriving from it a detailed accumulation history – that uses an adjoint-based method. The motivation of our work is the recent application of phase-sensitive radar which measures the vertical velocity of an ice column. The velocity is dependent on the history of subsequent snow accumulation, compaction and compression; in our inverse formulation of this problem, measured vertical velocity profiles can be utilized directly, thereby reducing the uncertainty introduced by ice-flow modelling. We first apply our method to synthetic data in order to study its capability and the effect of noise and gaps in the age–depth observations. The method is then applied to the ice core retrieved from James Ross Island, Antarctica. We show that the method is robust and that the results depend on the quality of the age–depth observations and the derived flow regime around the core site. The method facilitates the incorporation of increasing detail provided by ice-core analysis together with observed full-depth velocity in order to construct a complete climatic record of the polar regions.

Description: Sedimentary archives of climate and sea-level changes during the Holocene in the Rhone prodelta (NW Mediterranean Sea) Anne-Sophie Fanget, Maria-Angela Bassetti, Christophe Fontanier, Alina Tudryn, and Serge Berné Clim. Past Discuss., doi:10.5194/cp-2016-57,2016 Manuscript under review for CP (discussion: open, 0 comments) A 7.38 m-long sediment core was collected from the eastern part of the Rhone prodelta (NW Mediterranean) at 67 m water depth. A multi-proxy study (sedimentary facies, benthic foraminifera and ostracods, clay mineralogy, and major elements from XRF) provides a multi-decadal to century-scale record of climate and sea-level changes during the Holocene. The early Holocene is marked by alternative silt and clay layers interpreted as distal tempestites deposited in a context of rising sea level. This interval contains shallow infra-littoral benthic meiofauna (e.g. Pontocythere elongata, Elphidium spp., Quinqueloculina lata) and formed between ca. 20 and 50 m water depth. The middle Holocene (ca. 8.3 to 4.5 ka cal. BP), is characterized, at the core site, by a period of sediment starvation (accumulation rate of ca. 0.01 cm yr −1 ) resulting from the maximum landward shift of the shoreline and the Rhone outlet(s). From a sequence stratigraphic point of view, this condensed interval, about 35 cm-thick, is a Maximum Flooding Surface that can be identified on seismic profiles as the transition between delta retrogradation and delta progradation. It is marked by very distinct changes in all proxy records. Following the stabilization of the global sea level, the late Holocene is marked by the establishment of prodeltaic conditions at the core site, as shown by the lithofacies and by the presence of benthic meiofauna typical of the modern Rhone prodelta (e.g. Valvulineria bradyana, Cassidulina carinata, Bulimina marginata). Several periods of increased fluvial discharge are also emphasized by the presence of species commonly found in brackish and shallow water environments (e.g. Leptocythere). Some of these periods correspond to the multi-decadal to centennial late Holocene humid periods recognized in Europe (i.e. the 2.8 ka event and the Little Ice Age). Two other periods of increased runoffs at ca. 1.3 and 1.1 ka cal. BP are recognized, and are likely to reflect periods of regional climate deterioration that are observed in the Rhone watershed.

Description: How sensitive are modeled contemporary subsea permafrost thaw and thickness of the methane clathrates stability zone in Eurasian Arctic to assumptions on Pleistocene glacial cycles? Valentina V. Malakhova and Alexey V. Eliseev Clim. Past Discuss., doi:10.5194/cp-2016-66,2016 Manuscript under review for CP (discussion: open, 0 comments) Single-point simulations with a model for thermal state of subsea sediments driven by the forcing constructed from the ice core data show that the impact of initial conditions is lost after ~ 100 kyr. The time scales of temperature propagation in sediments and respective permafrost response are ~ 10–20 kyr which is longer than the present interglacial. The timings of shelf exposure during oceanic regressions and flooding during transgressions are important for representation of sediment thermal state and hydrates stability zone (HSZ). These timings should depend on the contemporary shelf depth (SD). During glacial cycles temperature at the top of sediments is a major driver of HSZ vertical boundaries change for SD of few tens of meters, while the pressure exerted by oceanic water becomes more important for larger SD. Thus, even the existence of HSZ and its disappearance might not be easily tied to oceanic transgressions and regressions.

Description: Impacts of Tibetan Plateau uplift on atmospheric dynamics and associated precipitation δ 18 O Svetlana Botsyun, Pierre Sepulchre, Camille Risi, and Yannick Donnadieu Clim. Past, 12, 1401-1420, doi:10.5194/cp-12-1401-2016, 2016 We use an isotope-equipped GCM and develop original theoretical expression for the precipitation composition to assess δ 18 O of paleo-precipitation changes with the Tibetan Plateau uplift. We show that δ 18 O of precipitation is very sensitive to climate changes related to the growth of mountains, notably changes in relative humidity and precipitation amount. Topography is shown to be not an exclusive controlling factor δ 18 O in precipitation that have crucial consequences for paleoelevation studies

Description: Constant wind regimes during the Last Glacial Maximum and early Holocene: evidence from Little Llangothlin Lagoon, New England Tablelands, eastern Australia James Shulmeister, Justine Kemp, Kathryn E. Fitzsimmons, and Allen Gontz Clim. Past, 12, 1435-1444, doi:10.5194/cp-12-1435-2016, 2016 This paper highlights that small dunes (lunettes) formed on the eastern side of a lake in the Australian sub-tropics at the height of the last ice age (about 21,000 years ago) and in the early part of the current interglacial (9–6,000 years ago). This means that it was fairly wet at these times and also that there were strong westerly winds to form the dunes. Today strong westerly winds occur in winter, and we infer that the same was also true at those times, suggesting no change in circulation.

Description: April–August temperatures in the Czech Lands, 1499–2015, reconstructed from grape-harvest dates Martin Možný, Rudolf Brázdil, Petr Dobrovolný, and Miroslav Trnka Clim. Past, 12, 1421-1434, doi:10.5194/cp-12-1421-2016, 2016 April–August temperature reconstruction for the Czech Lands based on grape-harvest dates in the 1499–2012 period constitutes a further important contribution to the better understanding of long-term spatiotemporal temperature variability in central Europe and includes the very long overlap period (1801–2012) used for calibration and verification, the consistent dominance of Pinot varieties through time, and the stability of vineyard management throughout the period reconstructed.

Description: Paleoclimate in continental northwestern Europe during the Eemian and early Weichselian (125–97 ka): insights from a Belgian speleothem Stef Vansteenberge, Sophie Verheyden, Hai Cheng, R. Lawrence Edwards, Eddy Keppens, and Philippe Claeys Clim. Past, 12, 1445-1458, doi:10.5194/cp-12-1445-2016, 2016 The use of stalagmites for last interglacial continental climate reconstructions in Europe has been successful in the past; however to expand the geographical coverage, additional data from Belgium is presented. It has been shown that stalagmite growth, morphology and stable isotope content reflect regional and local climate conditions, with Eemian optimum climate occurring between 125.3 and 117.3 ka. The start the Weichselian is expressed by a stop of growth caused by a drying climate.