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The dynamics of sea ice variability – role of the oceans

Periodic Reporting for period 1 - IceDynamO (The dynamics of sea ice variability – role of the oceans)

Reporting period: 2018-05-01 to 2020-04-30

For understanding the recent global warming, it is crucial to understand the climate changes of the past. The climate changed drastically numerous times during the history of Earth; there has been several degrees higher as well as lower average temperatures globally. If we manage to understand the underlying forcing mechanisms of these past changes and the links between them, it will be easier to evaluate to what extent the on-going trend is related to natural variations and how much is due to human activity. The Arctic region plays a particularly important role in the (paleo)climate research. It is one of the most sensitive areas with respect to the on-going global warming, and it is experiencing a warming trend that is greater than in any other region of the world. The summer sea-ice cover in the Arctic has decreased drastically in the last decades, and according to model simulations the area may become seasonally ice-free as early as around 2040–2050. Despite the extreme societal and environmental relevance of these recent changes in Arctic climate, our understanding of natural water mass and sea-ice variability and their response to external natural and human-induced forcing is scarce.

The overall objective of this project was therefore to reconstruct the variability of oceanic and sea-ice conditions on the Northeast Greenland shelf during the Holocene (our present interglacial, the last 11,700 years) and investigate their connection to the Greenland ice-sheet dynamics, ocean circulation and global climate.
In this project different climate proxy analyses were combined, in order to obtain a most comprehensive image of this highly coupled system. With the multi-proxy approach based on benthic foraminiferal assemblage-, geochemical- and sedimentological analyses of a marine sediment core, a high-resolution record of Holocene general oceanic, atmospheric and sea-ice conditions was developed. Radiocarbon datings, X-ray flurorescens data, grain size, stable isotope analysis and faunal assemblage analysis of benthic and planktic foraminifera allowed to infer changes in sea surface productivity, subsurface water temperatures, sea-ice conditions, Greenland Ice Sheet melting and thus, in the strength of the East Greenland Current on the East Greenland shelf over the last ca. 9400 years before present.

The results enhance the estimation of future responses of Arctic water masses to environmental changes. Thus, the work from this project has important implications not just for the community of paleo-scientists but provides crucial research-data for modellers in order to improve predictive climate models.
The outcome of the project provides new insights into the not yet resolved paleoceanographic evolution of the Northeast Greenland shelf. As the analyzed sediment core covers almost the whole time period of the Holocene, it provides a continuous record of changes in the strength of the East Greenland Current over the last ca. 9400 years before present on the Northeast Greenland shelf. The project has considerable relevance in long-term societal perspective: warming of the Arctic and diminishing sea ice may open new opportunities for shipping and societal development of Arctic regions and Greenland. Furthermore, as the changing oceanic environment affects arctic ecosystems, the results have the potential to contribute to the development of sustainable conservation and ecosystem-based management strategies.
A marine sediment core can reveal changes in the past climate. Image credit: Dr. Christof Pearce.