ALBERT

Description: Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.

Description: Atlantic Water (AW) advection plays an important role in climatic, oceanographic and environmental conditions in the eastern Arctic. Situated along the only deep connection between the Atlantic and the Arctic oceans, the Svalbard Archipelago is an ideal location to reconstruct the past AW advection history and document its linkage with local glacier dynamics, as illustrated in the present study of a 275 cm long sedimentary record from Woodfjorden (northern Spitsbergen; water depth: 171 m) spanning the last  ∼  15 500 years. Sedimentological, micropalaeontological and geochemical analyses were used to reconstruct changes in marine environmental conditions, sea ice cover and glacier activity. Data illustrate a partial break-up of the Svalbard–Barents Sea Ice Sheet from Heinrich Stadial 1 onwards (until  ∼  14.6 ka). During the Bølling–Allerød ( ∼  14.6–12.7 ka), AW penetrated as a bottom water mass into the fjord system and contributed significantly to the destabilization of local glaciers. During the Younger Dryas ( ∼  12.7–11.7 ka), it intruded into intermediate waters while evidence for a glacier advance is lacking. A short-term deepening of the halocline occurred at the very end of this interval. During the early Holocene ( ∼  11.7–7.8 ka), mild conditions led to glacier retreat, a reduced sea ice cover and increasing sea surface temperatures, with a brief interruption during the Preboreal Oscillation ( ∼  11.1–10.8 ka). Due to a  ∼  6000-year gap, the mid-Holocene is not recorded in this sediment core. During the late Holocene ( ∼  1.8–0.4 ka), a slightly reduced AW inflow and lower sea surface temperatures compared to the early Holocene are reconstructed. Glaciers, which previously retreated to the shallower inner parts of the Woodfjorden system, likely advanced during the late Holocene. In particular, topographic control in concert with the reduced summer insolation partly decoupled glacier dynamics from AW advection during this recent interval.

Description: Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and -climate change in central/northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. We present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), -salinity, and -ecosystem changes from the Little Belt (Site M0059) over the past ~ 8000 years, and evaluate the applicability of inorganic and organic proxies in this particular setting. Salinity proxies (diatoms, aquatic palynomorphs, ostracods, long chain diol index – LDI) show that lacustrine conditions occurred in the Little Belt until ~ 7400 cal. yr BP. A connection to the Kattegat at this time can be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish-marine conditions (more saline and warmer) of the Littorina Sea stage occurred within ~ 200 yr when the connection to the Kattegat became established (~ 7400 cal. yr BP). The different salinity proxies used here show similar trends in relative changes in salinity, but do often not allow quantitative estimates of salinity. The reconstruction of water temperatures is associated with particular large uncertainties and variations in absolute values by up to 8 °C for bottom waters and even up to 16 °C for summer surface waters. Concerning the foraminiferal Mg/Ca reconstruction, contamination in the deeper intervals may have led to an over-estimation of temperatures. Differences in results based on the lipid proxies (LDI and TEXL86) can partly be explained by the application of modern-day proxy calibrations in areas which experienced significant changes in depositional settings, in case of our study e.g. change from freshwater to marine conditions. Our study shows that particular caution has to be taken when applying and interpreting proxies in coastal environments, where water mass conditions can experience more rapid and larger changes than in open-ocean settings. Approaches using a multitude of independent proxies may thus allow a more robust paleoenvironmental assessment.

Description: Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and climate change in central and northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. Here we present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), paleosalinity, and paleoecosystem changes from the Little Belt (Site M0059) over the past  ∼  8000 years and evaluate the applicability of inorganic- and organic-based proxies in this particular setting. All salinity proxies (diatoms, aquatic palynomorphs, ostracods, diol index) show that lacustrine conditions occurred in the Little Belt until  ∼  7400 cal yr BP. A connection to the Kattegat at this time can thus be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish–marine conditions of the Littorina Sea stage (more saline and warmer) occurred within  ∼  200 years when the connection to the Kattegat became established after  ∼  7400 cal yr BP. The different salinity proxies used here generally show similar trends in relative changes in salinity, but often do not allow quantitative estimates of salinity. The reconstruction of water temperatures is associated with particularly large uncertainties and variations in absolute values by up to 8 °C for bottom waters and up to 16 °C for surface waters. Concerning the reconstruction of temperature using foraminiferal Mg  /  Ca ratios, contamination by authigenic coatings in the deeper intervals may have led to an overestimation of temperatures. Differences in results based on the lipid paleothermometers (long chain diol index and TEXL86) can partly be explained by the application of modern-day proxy calibrations to intervals that experienced significant changes in depositional settings: in the case of our study, the change from freshwater to marine conditions. Our study shows that particular caution has to be taken when applying and interpreting proxies in coastal environments and marginal seas, where water mass conditions can experience more rapid and larger changes than in open ocean settings. Approaches using a multitude of independent proxies may thus allow a more robust paleoenvironmental assessment.

Description: Atlantic Water (AW) advection plays an important role for climatic, oceanographic and environmental conditions in the eastern Arctic. Situated along the only deep connection between the Atlantic and the Arctic Ocean, the Svalbard Archipelago is an ideal location to reconstruct the past AW advection history and document its linkage with local glacier dynamics, as illustrated in the present study of a sedimentary record from Woodfjorden (northern Spitsbergen) spanning the last ~ 15 500 years. Sedimentological, micropalaeontological and geochemical analyses were used to reconstruct changes in marine environmental conditions, sea-ice cover and glacier activity. Data illustrate a partial breakup of the Svalbard–Barents–Sea Ice Sheet from Heinrich Stadial 1 onwards (until ~ 14.6 ka BP). During the Bølling-Allerød (~ 14.6–12.7 ka BP), AW penetrated as a bottom water mass into the fjord system and contributed significantly to the destabilisation of local glaciers. During the Younger Dryas (~ 12.7–11.7 ka BP), it intruded into intermediate waters while evidence for a glacier advance is lacking. A short-term deepening of the halocline occurred at the very end of this interval. During the early Holocene (~ 11.7–7.8 ka BP), mild conditions led to glacier retreat, a reduced sea-ice cover and increasing sea surface temperatures, with a brief interruption during the Preboreal Oscillation (~ 11.1–10.8 ka BP). During the late Holocene (~ 1.8–0.4 ka BP), a slightly reduced AW inflow and lower sea surface temperatures compared to the early Holocene are reconstructed. Glaciers, which previously retreated to the shallower inner parts of the Woodfjorden system, likely advanced during the late Holocene. In particular, as topographic control in concert with the reduced summer insolation partly decoupled glacier dynamics from AW advection during this recent interval.

Description: The marine Eemian (marine oxygen-isotope substage 5e: MIS 5e) is represented by shallow-water deposits in southern and western Denmark, while relatively deep-water environments occurred to the north and north-east, where complete interglacial successions seem to be present. We present an overview of the marine Eemian deposits in Denmark, and discuss in more detail indications of climate variability, both for the late Saalian and within the Eemian.

Description: Studies of marine records from the northwestern European shelf and the northern North Atlantic suggest that last interglacial environments were less stable in this area than in the mid-latitude Atlantic. The influx of Atlantic water masses to the northern North Atlantic was generally higher, and the meridional temperature gradient was steeper, during the last interglaciation than during the Holocene. Strong north–south sea-surface-temperature gradients during the early Weichselian indicate a generally low influx of Atlantic water to the northern North Atlantic, even during interstades.

Description: Benthic foraminifera and stable isotope data from the last interglaciation (Eemian, substage 5e) from a borehole at Skagen, Denmark, provide evidence for major environmental and hydrographic changes during this period. During the first millennium of the Eemian, water masses covering northern Denmark became gradually warmer. Temperate conditions prevailed during most of the interglaciation, but these were interrupted by two periods with decreased water temperatures. The first cooling (Event S-1) was not very distinct at Skagen, but the second (Event S-2), seen in both the foraminiferal and oxygen isotope record, represents a large shift to subarctic conditions. Carbon isotopes indicate a change in ocean circulation during both events. No comparable climate variations are seen within the Holocene record at the site. The final cooling of the water masses associated with the substage 5e/5d boundary occurred within a few hundred years. These last interglacial climatic changes were probably caused by variations in strength and/or position of the North Atlantic Drift, possibly as a result of varying vigor of the Atlantic conveyor. In addition, minor variations in the fossil assemblages also indicate fluctuations in the inflow of Atlantic water to the Skagerrak–Kattegat area during the warm intervals of substage 5e.

Description: Benthic foraminiferal populations were studied in a shallow bay of San Salvador Island, the Bahamas. Surface sediments and marine macrophytes were collected from 14 sample sites along a 500 m transect at Grahams Harbour to investigate the foraminiferal assemblage in each microhabitat and to test the link between dead foraminiferal test accumulation patterns and living epiphytic and sedimentary foraminiferal assemblages, macrophyte distribution, and environmental gradients. The analyses include grain size measurements, macrophyte biomass quantification, and qualitative and quantitative studies of benthic foraminifera. The foraminifera found attached to macrophytes differed between macrophyte habitats. However, a correlation between these living communities and the dead assemblages in the sediments at the same sites could not be observed. Principal component analysis (PCA) and redundancy analysis (RDA) suggest that the presence of the macroalgae Halimeda explains 16 % of the residual faunal variation in the dead foraminiferal assemblage after the effects of sorting according to fall speed are partialled out. The RDA also reflects a positive correlation between foraminifera larger than 1.0 mm in diameter and the 0.25–0.5 mm sediment grain size, indicating sedimentological processes as the main factor controlling the sedimentary epiphytic foraminiferal assemblages. These sedimentary processes overprint most effects of ecological features or macrophyte-specific association.

Description: The mass loss from the Greenland Ice Sheet has increased over the past two decades. Marine-terminating glaciers contribute significantly to this mass loss due to increased melting and ice discharge. Rapid retreat periods of these tidewater glaciers have been linked to the concurrent inflow of warm, Atlantic derived waters. However, little is known about the variability of Atlantic-derived waters within these fjords, due to a lack of multi-annual, in situ measurements. Thus, to better understand the potential role of ocean warming on glacier retreat, reconstructions that characterize the variability of Atlantic water inflow to these fjords are required. Here, we investigate foraminiferal assemblages in a sediment core from Upernavik Fjord, West Greenland, in which the major ice stream Upernavik Isstrøm terminates. We investigate the environmental characteristics that control species diversity and derive that it is predominantly controlled by changes in bottom water variability. Hence, we provide a reconstruction of Atlantic water inflow to Upernavik Fjord, spanning the period 1925–2012. This reconstruction reveals peak Atlantic water inflow during the 1930s and again after 2000, a pattern that is similar to the Atlantic Multidecadal Oscillation (AMO). We compare these results to historical observations of front positions of Upernavik Isstrøm. This reveals that inflow of warm, Atlantic-derived waters indeed likely contributed to high retreat rates in the 1930s and after 2000. However, moderate retreat rates of Upernavik Isstrøm also prevailed in the 1960s/1970s, showing that retreat continued despite reduced Atlantic water inflow, albeit at a lower rate. Considering the link between bottom water variability and the AMO in Upernavik Fjord and the fact that a persistent negative phase of the AMO is expected for the next decade, Atlantic water inflow into the fjord may decrease in the next ~ 10 years.