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Exploring the Depths of Ancient Oceans with Science
As a paleoceanographer, I delve into sediment cores and fossil records to uncover hidden stories of the ocean's past. By weaving together these findings, I shed light on the future of our planet's climate. I am passionate about my work and excited to share it with you.
Researcher
Unlock the secrets of the ocean with foraminifera – the ultimate paleoceanography tool
Foraminifera, also known as forams, are single-celled organisms found in marine environments. They are characterized by a shell, or test, which is typically made of calcium carbonate or organic material. Foraminifera is an essential group of microfossils used by micropalaeontologists and geologists to study the history of the Earth's oceans and climate. By analyzing the composition and distribution of foraminifera in marine sediments, scientists can reconstruct past environmental conditions, such as temperature, salinity, and nutrient levels. Foraminifera are also important indicators of ocean health and are used to monitor the impacts of climate change and human activities on marine ecosystems.
While general trends in the inflow of Atlantic Water (AW) to the European Arctic over the present interglacial (the Holocene) are well known, regional changes in climate and the AW current and subsequent environmental responses are less well established. In particular, there is only limited knowledge on the development of ocean currents after the last deglaciation. Here, to better understand past water mass dynamics and their effects on sea ice cover and the environment throughout the Holocene, we present a multiproxy record from core OCE2019-HR7-GC retrieved from the southwestern Svalbard inner shelf, a highly dynamic frontal area influenced by different ocean currents and local water masses. For sea ice reconstructions, we focus on the specific sea ice biomarker IP25 in combination with the phytoplankton biomarkers dinosterol and brassicasterol. We further reconstruct surface and bottom water temperatures using alkenones and Mg/Ca and prevailing water masses using foraminifera assemblages. Finally, we compare our sea ice and temperature records with published marine sediment and ice core data from the area. We observe extensive sea ice cover between 11 and 10.2 kyr BP, which was likely linked to the Preboreal Oscillation. Based on our reconstructions, the period between 10 and 7 kyr BP was characterized by the warmest Holocene conditions on the SW Svalbard shelf. This interval is also associated with high surface water productivity and an enhanced AW influx that drove strong erosive activity at the bottom. After 6.5 kyr BP, the SW Svalbard shelf was characterized by a dynamic environment with cold and unstable conditions that lasted until 3.5 kyr BP. After 3.5 kyr BP, we observed an increase in sea ice cover and iceberg rafting over our site once more, which likely indicated seasonally fluctuating ice margins, with low AW influx, which lasted until 2.2 kyr BP. A brief warm period accompanied by strong bottom currents occurred between 2.2 and 1.8 kyr BP. The environment returned to a colder state with the presence of sea ice until 1.5 kyr BP, which was followed by warmer conditions between 1.5 and 1 kyr BP.
GREENLAND SEA MYSTERY
The flow of the Atlantic Water (AW) via the Return Atlantic Current (RAC) regulates the oceanographical conditions in the Northwestern (NW) Greenland Sea in the Fram Strait. As the intensity of the RAC might significantly influence both deep-water formation in the area and the stability of the Northeast Greenland Ice Sheet (NE GIS), knowledge of its variability in the past is important. Here we present a reconstruction of the paleoceanographic forcing of the AW on climatic conditions and associated environmental changes in the NW Greenland Sea by means of foraminiferal assemblages, stable (oxygen and carbon) isotopes, and various sedimentological parameters from sediment core GR02-GC retrieved from NE Greenland continental slope (1170 m water depth). Our data indicate an almost continuous presence of AW in the NW Greenland Sea during the last 35 kyr BP. Two peaks of low planktic δ18O values at ∼34.5 and 33 kyr BP are interpreted as meltwater signals associated with warm AW-induced melting of the adjacent NE GIS. The NE GIS advanced between 32 and 29 kyr BP, resulting in reduced meltwater influx to the NW Greenland Sea. Increased iceberg calving and melting after 29 kyr BP, were probably linked to surface warming and glacier advance to the shelf-break lasting until 23.5 kyr BP. During the Last Glacial Maximum, the extensive sea ice cover was associated with the presence of subsurface AW at the study site. During the Bølling–Allerød (B/A, ∼14.6–12.7 kyr BP) strong melting of glaciers and sea ice was probably caused by the combined effect of the B/A warming and the flow of warm AW. The RAC was weakened during the Younger Dryas (∼12.8–11.7 kyr BP), which reduced the advection of warm AW to the NW Greenland Sea. After 11.7 kyr BP, the RAC reached its modern strength, whereas, during the Holocene Thermal Maximum, it reached its maximum strength for the study period. In addition, short-term weakening of AW inflow to the core site was observed, especially at 10.5, 8.5, and 5.8 kyr BP.
