Changes in ocean circulation, sea-ice cover and glacial extent: perspectives from Greenland

• Main Author: Davies, Joanna Martin
• Format: Book
• Language: English
• Published: Aarhus University 2024
• Subjects: Arctic; Foraminifera*; Greenland; Ice Sheet; Nares strait; Phytoplankton; Sea ice
• Online Access: https://pure.au.dk/portal/en/publications/41810b07-c737-4da0-a01d-e44ac928783d

It is unequivocal that our climate is changing, and the Arctic is warming at several times the global average. The consequences of these changes are broad and severe: glaciers are retreating, sea ice is diminishing in thickness and extent and ocean temperatures are warming. However, our understanding of the processes governing these changes is limited by the relatively short length of instrumental records. Thus, the aim of this PhD is to extend these records, specifically to understand the processes that link the cryosphere and oceans, by examining previous periods of climatic change during the Holocene. In this PhD, two new multi-proxy (benthic foraminifera, sea-ice biomarkers, XRF, CT scans) studies, that span the Holocene, are presented. From the Northeast Greenland continental shelf (Paper 1; marine sediment core DA17-NG-ST08-092G), results indicate that deglaciation occurred at least as early as 12.5 ka cal BP, and likely before 13.4 ka cal BP. The inflow of warm Atlantic water most likely played a key role in the seemingly early retreat of ice in this area. Following this period, several advances and retreats of the ice sheet occurred, again linked to changing inflow of Atlantic water to the shelf. The inflow of Atlantic water was stronger during the early Holocene than today, with a reduction of the influence of the Atlantic water occurring over the last 8000 years. At the opening to Inglefield Bredning, Northwest Greenland (Paper 4; sediment core LK19-ST5-5G), biomarkers (IP25 and phytoplankton sterols) reveal changes in sea-ice cover that occurred during the Holocene, relating specifically to the formation and stability of the North Water polynya, which is closely linked to ice arches in Nares Strait. Ongoing work for this manuscript is focused on setting up alkenone methodology at Aarhus University, with the aim of assessing their use as an environmental proxy in this region. Such reconstructions are dependent on a solid understanding of the environmental parameters governing the behaviour of proxies. ...