Deepwater evolution in the inner Labrador Sea over the last 30 ka BP (DEEPTELLs)

• Applicants: Dr. Janne Repschläger; Professor Dr. Ralph Schneider
• Subject Area: Palaeontology
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 326649832

The formation of Labrador Sea Water (LSW) through deepwater convection in the Labrador Sea is supposed to stabilize the modern ocean circulation since about 7 ka BP. Despite its importance in the modern ocean circulation, it is suggested that deepwater formation in the Labrador Sea is a unique feature in the Holocene and did not occur during the last Glacial period. Instead, low glacial delta13C signatures reconstructed from benthic foraminifera in sediment cores off Cape Hatteras in the outflow pathway of deepwater from the Labrador Sea are interpreted as southern sourced deepwater that reached up to high northern latitudes. This simplified concept is recently questioned, as changes in the end member composition of the glacial deepwater originating from the North Atlantic region and even deepwater formation in the Labrador Sea need to be considered. Previous studies from the Labrador Sea are based on sedimentological and surface water reconstruction, thus little is known about the glacial and deglacial deepwater composition and -structure in the Labrador Sea. In the proposed study we aim to reconstruct the water mass structure and composition in the Labrador Sea during the last Glacial and the Deglaciation in order to test whether LSW formation was active during the last Glacial and which importance it had for the glacial state of the Atlantic Overturning Circulation (AMOC). The reconstructions will be conducted on four sediment cores taken in the Inner Labrador Sea at water depth between 1200 and 3300 m, covering the different deepwater masses that are filling the Labrador Sea. To identify potential end member composition changes, delta13C and delta18O analyses on benthic foraminifera and Mg/Ca temperature reconstruction from benthic foraminifera and ostracods will be used. The results of the study can help to gain a better understanding of the importance of the Labrador Sea for the Glacial and Deglacial global AMOC changes and for more stable AMOC modes. This will be also pivotal to assess the importance of the Labrador Sea under anthropogenic forced climate warming and should help to further test and improve climate models used to predict future climate change.

• DFG Programme: Research Grants
• Cooperation Partners: Dr. Nils Andersen; Dr. Dieter Garbe-Schönberg