ALBERT

Description: Albedo – the reflectivity of a surface - is an important component in the energy budget, impacting the local to global climate. Data from nadir-viewing satellites can be combined with bidirectional reflectance distribution function (BRDF) data from multi-angular observation platforms to achieve realistic albedo values that acknowledge anisotropy. In my thesis, I evaluated how the land surface albedo varied on spatial and temporal scales during the snow-free period on Disko Island, Greenland. I examined how the albedo differed among the vegetation classes. Concerning the methodology, I assessed how the combination of MODIS BRDF data with Landsat 8 (L8) or Sentinel-2 (S2) influenced the albedo. The study area was located at the southern tip of Disko Island (69.27 °N, -53.47 °E) in West Greenland and covered a wetland and a range of tundra vegetation. I analysed automatic weather station (AWS) data from 2013 to 2022 and conducted mobile albedo measurements in August and September 2022 to examine the temporal and spatial variability. For the period from June to September 2022, I derived the L8 and S2 based albedo with inclusion of MODIS BRDF and narrow to broadband conversion and analysed their variability with regard to vegetation classes. In the snow-free period, the albedo increased from a monthly mean of 0.16 in June to 0.19 in September in the AWS data. The mobile measurements ranged from 〈 0.10 above bare soil and water to 〉 0.23 above areas dominated by lichen, Salix glauca or Equisetum arvense. The satellite-based albedo revealed temporally variable, significant correlations to normalised difference vegetation and moisture indices that reached values 〉 0.5 in the fen and wet heath class on several days. The albedo of shrubs was not notably smaller than other vegetation types but partly 0.01-0.05 above them in both the mobile measurements and the satellite-derived albedo. This finding challenges the assumption that shrubification causes climate forcing in all circumstances. The albedo of L8 and S2 differed to each other and the local data (root-mean-square error 0.04-0.14). The BRDF correction increased the albedo by 0.01 on average compared to nadir reflectance. L8 was better in reproducing the expected temporal and spatial variability of albedo than S2, which displayed less variability. S2 seemed to be more sensitive to atmospheric effects of haze and clouds influencing albedo. Thus, L8 seemed more suitable to calculate albedo in the study area. Though there were some methodological limitations, this thesis highlights aspects that should be considered when analysing albedo or jointly using L8 and S2 in high latitude regions.

Description: Data derived from Core SG-1b (coordinates: 38°21'9.46'' N, 92°16'24.72'' E) which was drilled within the framework of a Sino-German cooperation project in 2008. Attached Excel spreadsheet contains to data sets: 1. Data: Depth, Age, Sedimentation Rate and ln(Rb/Sr) ratio 2. Age model: Depth, Age Abstract: To contribute to a better understanding of Neogene climate evolution in Central Asia, we here present the first orbitally tuned time scale for a drillcore record from the Qaidam Basin (NE Tibetan Plateau) that consists of lacustrine sediments and spans the late Pliocene to early Pleistocene (~3.3 to 2.1 Ma). Our tuning of Core SG-1b is based on the ln(Rb/Sr) ratio derived from XRF core scanning and grain-size distribution data that trace wet-dry climate alternations predominantly paced by orbital obliquity. Based on our ln(Rb/Sr) record, obliquity-precession interferences persisted during the mid-Pliocene warm period, but disappeared during the early Pleistocene. This could indicate that over the course of the late Pliocene a low-latitude-derived climate modulator gained an increasingly prominent role in shaping the environment of the Qaidam paleolake. At the same time, the consistent presence of the precession signal during the early Pleistocene hampers a refinement of the entire tuning on precession time scales. The inferred changes in sedimentation rate from the late Pliocene to the early Pleistocene indicate a long-term decrease in sediment supply into the Qaidam paleolake. This finding is in line with the previously proposed notion of a long-term aridification trend across the Plio-Pleistocene transition in Central Asia.

Description: Bulk-rock carbon isotopes (d13C), redox-sensitive trace elements and carbonate content measured in the Bodudd section in Gotland, Sweden. The age of the section is Ludfordian (Ludlow, Silurian) and it was deposited on a tropical carbonate platform. Funded by Deutsche Forschungsgemeinschaft project JA 2718/3-1.

Description: These are the supplementary datasets for the manuscript: Drury, A.J., Liebrand, D., Westerhold, T., Beddow, H., Hodell, D., Rohlfs, N., Wilkens, R.H., Lourens, L., 'History of South Atlantic carbonate deposition since the Oligocene (30-0 Ma)', in final preparation for submission Climate of the Past

Description: Sediment properties of a 223-m-long drill core from the Ejina basin, NW China, for reconstructing the palaeoenvironmental history of a part of the Gobi Desert. The sediment study is part of the Q-TiP project (Quaternary Tipping Points of Lake Systems in the Arid Zone of Central Asia) in the frame of the CAME II program (BMBF funded).

Description: This dataset includes planktic foraminifera (Globigerinoides ruber sensu-stricto) stable oxygen isotope and Mg/Ca data from IODP Expedition 353, Sites U1446 and U1448 across Marine Isotope Stage 5 (140-70 ka). Additionally, included is a time-series of annual change in precipitation as emulated by PaleoPGEM across 6 large-scale low-latitude regions throughout Marine Isotope Stage 5 (140-70 Ka).

Description: We compiled modern and fossil relative abundance of coccolithophore species Florisphaera profunda from published and unpublished datasets, along with ocean environmental variable data from satellite remote sensing and physical measurements. The database includes relative abundances of F. profunda in sediment trap (n = 26) and core-top (n = 1258), and sediment core samples (n = 104). Downcore data covers the Last Glacial Maximum (n = 94, 24-19 ka) or the Mid-to-Late Holocene (n = 77, 〈6 ka). This database allows studying modern and past biogeography of F. profunda as a response to changing ocean and climate conditions, “Quantitative reconstruction of primary productivity in low latitudes during the last glacial maximum and the mid-to-late Holocene from a global Florisphaera. profunda calibration dataset” (Hernández-Almeida et al., 2018).

Description: This dataset presents the XRF core-scanning record from International Ocean Discovery Program (IODP) Site U1478 off the Limpopo River mouth (Mozambique Channel, SW Indian Ocean) spanning the past c. 4 Ma. Site U1478 was drilled in the northernmost Natal Valley, on the Inharrime Terrace (25°49.26′ S; 34°46.16′ E) at a water depth of 488 m below sea level. The XRF core scanning of the ~257-m-long splice for Site U1478 was carried out using an Itrax Core Scanner at Lamont-Doherty Earth Observatory Core Repository, Columbia University (USA). In total, 239 sections (archive halves) were scanned at a voltage of 30 kV and a tube current of 55 mA using a Cr tube and employing an exposure time of 2 seconds. Measurement spacing was set at 2 mm, with downcore and crosscore slit sizes set at 2 mm and 2 cm, respectively. The individual element counts were normalized using the ratio of raw total counts of a given element to the total counts of all processed elements for the respective measurement position. To eliminate non-linear matrix effects and constant-sum constraints, log ratios were applied on the elemental ratios. The age model of Site U1478 is based on cyclostratigraphic analysis of the XRF-based log(Ti/Ca) record and its tuning to ice-volume, precession and eccentricity cycles.

Description: Seven different labs XRF scanned the same seven marine sediment sections. Additionally, four labs XRF scanned pellets that had known compositions determined by ICP-ES and ICP-MS. These datasets contain the XRF scanning results of the seven sediment section and four pellets. The seven 1.5 m core sections of marine sediment core used in this study were drilled during Integrated Ocean Drilling Program (IODP) Expedition 346 at Site U1424 in the Japan Basin (40°11.39'N, 138°13.90'E, 2808 m water depth) and Site U1425 on the Yamato Rise (39°29.43' N, 134°26.55' E, 1909 m water depth). The sections selected (Hole U1424C Sections 1H4, 2H5, 3H5 and Hole U1425C Sections 2H3, 2H4, and 2H6, and 3H6) cover a range of sediment compositions. U-channels extracted continuous marine sediment approximately 1 cm thick from the center of each split core section. One lab scanned sections from different holes at the same sites (U1424A, U1425B, and U1425D) that were stratigraphically aligned with the sections listed above. Over the course of four years (2014 to 2017), the set of seven u-channels was shipped around the world to seven labs with XRF scanners including, in no particular order, the Kochi Core Center at Kochi University (Japan), IODP Core Repository at Texas A&M University (U.S.A.), Nanjing Normal University (China), Rosenstiel School of Marine and Atmospheric Science at the University of Miami (U.S.A.), ETH Zurich (Switzerland), Woods Hole Oceanographic Institution (U.S.A.), and the Royal Netherlands Institute of Sea Research (The Netherlands). We intentionally do not identify which lab generated which scans, as many of the variables (e.g., X-ray tube aging, detector aging, and/or dehydration of the core material) could affect any instrument at various times or be exacerbated during the transit between labs. Instead, we label the XRF scans #1-#7 in the order in which they were scanned. The lead investigators overseeing the XRF scanning in these labs were shipboard participants on IODP Expedition 346 and are among the authors of this paper. The only instructions to each lab were "to XRF scan the seven sediment sections at 1mm or 2mm resolution using the approach and elements typical for paleoceanographic research performed in your lab." To emulate variations in the XRF results that have been previously published, these simple guidelines were intentionally broad and general to determine the degree of intercomparability between the labs amongst all the different settings and nuances of XRF scanning. The labs used various types and different generations of XRF scanning instruments (4 Avaatech Core Scanners, 2 ITRAX Core Scanners, and 1 Geotek Core Scanning Logger) with different X-ray sources (Rhodium, Molybdenum). Three of the labs scanned the cores at two or three excitation energies (e.g., 10 kV, 30 kV, and 50 kV). Each lab reported a different suite of elements, but all included Ca, Fe, K, Mn, Si, Sr, Ti, and Zr. Six labs also reported Al, Br, Cr, Cu, Ni, Pb, Rb, S, and Zn and five labs reported and Ba, Cl, Ga, Mo, V, and Y. In addition to the seven core sediment sections, we freeze-dried and powdered four discrete samples that were pressed into disc-shaped pellets about 2 cm in diameter from nearby Core MD01-2407 on the Oki Ridge (37°04'N, 134°42'E, 932m water depth). The four samples have a similar matrix to the seven sediment sections scanned in this study. The four samples from Core MD01-2407 covered a range of sediment types (calcareous, siliceous, light-, and dark-colored; Kido et al., 2007) that span the dynamic range of at least Fe and Ca element cps scanned for this study. A set of four pellets was sent to four of the seven labs (1 ITRAX and 3 Avaatech) involved in the study to be scanned using the same instrument parameters they used on the sediment sections. Three labs used the same instrument and parameters used for the sediment section, but the fourth lab replaced the X-ray tube in between scanning the pellets and sediment sections. The major and trace element concentrations of the pellets were also analyzed by inductively coupled plasma (ICP)-optical emission spectrometry (OES) and ICP-mass spectrometry (MS) in the Analytical Geochemistry Facilities at Boston University, Boston, MA, USA. The ICP analyses had ~2% precision and a standard reference material analyzed as an unknown alongside the samples was accurate within precision.

Description: Palynology data and analysis for branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Point Margaret (Southern Australia), respectively, were used to estimate the mean annual air temparature during the Paleocene-Eocene Thermal Maximum.

Description: Global climate cooled from the early Eocene hothouse (~52-50 Ma) to the latest Eocene (~34 Ma). At the same time, the tectonic evolution of the Southern Ocean was characterized by the opening and deepening of circum-Antarctic gateways, which affected both surface- and deep-ocean circulation. The Tasmanian Gateway played a key role in regulating ocean throughflow between Australia and Antarctica. Southern Ocean surface currents through and around the Tasmanian Gateway have left recognizable tracers in the spatiotemporal distribution of plankton fossils, including organic-walled dinoflagellate cysts. This spatiotemporal distribution depends on both the physico-chemical properties of the water masses and the path of surface-ocean currents. The extent to which climate and tectonics have influenced the distribution and composition of surface currents and thus fossil assemblages has, however, remained unclear. In particular, the contribution of climate change to oceanographic changes, superimposed on long-term and gradual changes induced by tectonics, is still poorly understood. To disentangle the effects of tectonism and climate in the southwest Pacific Ocean, we target a climatic deviation from the long-term Eocene cooling trend, the Middle Eocene Climatic Optimum (MECO; ~40 Ma). This 500-thousand-year-long phase of global warming was unrelated to regional tectonism, and thus provides a test case to investigate the ocean's physiochemical response to climate change alone. We reconstruct changes in surface-water circulation and temperature in and around the Tasmanian Gateway during the MECO through new palynological and organic geochemical records from the central Tasmanian Gateway (Ocean Drilling Program Site 1170), the Otway Basin (southeastern Australia) and the Hampden Beach section (New Zealand). Our results confirm that dinocyst communities track specific surface-ocean currents, yet the variability within the communities can be driven by superimposed temperature change. Together with published results from the east of the Tasmanian Gateway, our new results suggest a shift in surface-ocean circulation during the peak of MECO warmth. Simultaneous with high sea-surface temperatures in the Tasmanian Gateway area, pollen assemblages indicate warm temperate rainforests with paratropical elements along the southeastern margin of Australia. Finally, based on new age constraints we suggest that a regional southeast Australian transgression might have been coincident with the MECO.

Description: The Atlantic Meridional Overturning Circulation (AMOC) helps regulate the transport and storage of a large reservoir of heat and carbon, and therefore plays an essential role in climate change past and present1. Authigenic uranium deposition in deep-sea sediments is a sensitive redox tracer2,3 that can shed light on bottom water oxygen, carbon storage and, in certain circumstances, water mass distributions in the deep ocean4-7. Here, we combine new and published authigenic uranium data to reconstruct oxygenation since the last ice age in the east and west basins of the North Atlantic Ocean. Overall, the glacial deep North Atlantic was less well oxygenated compared to the Holocene, suggesting a higher ocean carbon inventory and important contribution to the global sequestration of CO2. We find that lower oxygen levels occurred in the deepest locations in the western basin, while substantially lower-oxygen waters were present throughout the northeast Atlantic. Our findings indicate that lower oxygen levels and correspondingly greater carbon storage were persistent features of the last glaciation and deglaciation in the deep North Atlantic Ocean, particularly in the eastern basin. This zonal emphasis is likely related to the farther advance and greater infilling in the east of deep waters originating from the Southern Ocean.

Description: The data set has been obtained on gravity core M125-67-4 from off the Jequitinhonha River, East Brazil. The obtained proxies described the hydrological conditions in the river's hinterland over the past ~ 5000 years as measure of fluctuations in the South American Summer Monsoon intensity. XRF-derived K/Al ratios and mineral phases determined by XRD reflect weathering state in the hinterland; high K/Al ratio and low kaolinite contents indicate dry conditions (and vice versa for low K/Al and high kaolinite conditions). Hydrogen isotopes are interpreted to primarily reflect precipitation amount, with low values indicating more precipitation.

Description: Multi-proxy records from two deep-sea sediment cores (IODP 353-U1446 and U1448) of the stable oxygen isotope composition (N. dutertrei) and trace element ratios (G. ruber ss, N. dutertrei) measured in planktic foraminifera, foraminiferal percent abundance and bulk sediment elemental variations gained from portable-XRF. These records are inferred to capture Indian Summer Monsoon river runoff across Marine Isotope Stage 5/6 (70-140 thousand years ago).

Description: We collected pelagic sediments from Holes A and B of IODP Site 342-U1407 that accumulated on the Southeast Newfoundland Ridge that spanned the Early Cenomanian to Early Turonian. In this study, we reconstruct the paleoceanographic changes before, during, and after Oceanic Anoxic Event 2 (OAE2) to isolate the triggers behind the widespread deposition of organic matter (OM) during this time. We combined the stable isotopes of bulk organic carbon, total organic carbon, total inorganic carbon, major and trace elements, and abundances of microfossils (benthic foraminiferal, biserial heterohelicid foraminifera, and radiolarians) to characterize the sediments. Biomarker indices were also calculated to determine the source and thermal maturity of the OM.

Description: The latest Cenomanian to early Turonian sedimentary record recovered at IODP Site 369-U1513 in the Mentelle Basin (SE Indian Ocean, paleolatitude about 60°S at 85 Ma) is studied to interpret the paleoceanographic evolution across the Oceanic Anoxic Event 2 (OAE 2) in the Southern Hemisphere. Here we present the planktonic and benthic foraminifera, radiolaria and calcispheres distribution and absolute abundances, the calcareous nannofossils distribution, the CaCO3 content, the bulk carbonate carbon and oxygen stable isotope data and the Total Organic Carbon values from IODP Holes 369-U1513A and 369-U1513D. The data presented here permit interpretation of the dynamics of the water mass stratification and document a reduced water mass stratification with alternating episodes of enhanced surface water productivity and variations of the thickness of the mixed layer across the OAE 2.

Description: The data include temperature proxy data (TEX86, MBT, brGMGT-I, NLR) and palynology (dinocyst assemblage data) for two coastal sections in the Australo-Antarctic Gulf. The stratigraphy of these sections is described in Frieling et al. (2018). The new data were generated to provide detailed multi-proxy temperature reconstructions for the region. A combination of organic geochemistry (lipid biomarker) analyses and palynology (mainly dinoflagellate cysts (dinocyst)) were conducted. A paper describing the results has been submitted (doi supplied when available). Sediment samples were acquired (by hand) during a field campaign to the coastal outcrop section at Point Margaret, Australia (-38.724667 N, 143.176389 E, 0m elevation) 14-28th of February 2016. Core samples from the Latrobe-1 borehole (-38.693056 N, 143.150000 E; drilled in 1963, ca. 20m elevation) were acquired from the geological survey core repository (Melbourne) during the same trip. From these sediment samples we quantified isoprenoid and branched glycerol dialkyl glycerol tetraethers (isoGDGTs) and branched glycerol monoalkyl glycerol tetraethers (brGMGTs) from organic total lipid extracts using ultra high performance liquid chromatography – mass spectrometry (UHPLC-MS) analyses. Furthermore, we used standard palynological techniques to obtain nearest living relative data from pollen and spore assemblages (methodology follows Huurdeman et al. 2021). Dinoflagellate cyst (dinocyst) assemblages were analysed from the same residues and here provided as relative abundances of ecogroups. All measurements and analyses were conducted in the organic geochemistry and palynology labs at Utrecht University, Netherlands between 2016 and 2018.

Description: The cyclic growth and decay of continental ice sheets can be reconstructed from the history of global sea level. Sea level is relatively well-constrained for the Last Glacial Maximum (LGM, 26,500-19,000 years ago, 26.5-19 ka) and the ensuing deglaciation. However, sea-level estimates for the period of ice-sheet growth before the LGM vary by 〉 60 m, an uncertainty comparable to the sea-level equivalent of the contemporary Antarctic Ice Sheet. Here we constrain sea level prior to the LGM by reconstructing the flooding history of the shallow Bering Strait since 46 ka. Our data constraint on Bering Strait flooding are nitrogen isotope measurements in organic matter bound in the planktonic foraminifer Neogloboquadrina pachyderma from four sediment cores in the Arctic Ocean, dating back to ~50,000 years before present. These data extend the previous measurements of Farmer et al., 2021 (https://doi.org/10.1038/s41561-021-00789-y). We additionally provide new Bayesian age-depth models for each sediment core based on existing radiocarbon (14C) measurements on N. pachyderma. The nitrogen isotope data are compared with a suite of reconstructions of global mean sea-level and relative sea level at the Bering Strait from glacial isostatic adjustment modeling covering the last 120,000 years.

Description: The Paleocene-Eocene Thermal Maximum (PETM) is the most studied global warming event of a series of Paleocene-Eocene carbon cycle perturbations called hyperthermals. PETM origins have been associated with volcanic-related carbon emissions; however, other carbon cycle feedbacks were required to develop a large hyperthermal such as the PETM. The orbital configuration in which the PETM occurred is still unclear despite possible orbital controls on the PETM triggering. This dataset contains X-Ray Fluorescence (XRF) data (Fe, Ca, and Si) from Contessa Road (Italy), a sedimentary section with reduced calcium carbonate dissolution compared to deep ocean sites. Astrochronological age models and probabilistic assessments reveal that the PETM onset appeared close to both short and long eccentricity maxima, which suggests that orbitally controlled insolation variations may have thermally destabilized carbon reservoirs that worked as PETM positive carbon cycle feedbacks.