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Sea-ice variability around Greenland (G-ICE)

Synopsis: The overall purpose is to improve our basic understanding of processes determining sea-ice cover and variability, which is needed for a better prediction of the fate of Arctic sea ice in a warmer world. This is done through establishing longer time series of sea ice over recent centuries and millennia, focussing on the circum Greenland margin.

Objective: The recent Arctic sea-ice decline has been related to the ongoing global warming, but the actual diminution of sea ice has been much greater than foreseen in coupled climate models and a better understanding of the mechanisms governing sea-ice cover is clearly necessary. Yet, the natural variability of the Arctic sea ice is still not well understood, and we do not in fact know how realistic the predicted near-future disappearance of Arctic summer sea ice is. Satellite records are too short to represent the actual sea-ice variability through time and may correspond to a transient, non-equilibrium state. Thus, the preindustrial “baseline” of natural sea-ice cover is virtually unknown. This is particularly critical as the few available reconstructions of Arctic sea ice tend to suggest that the recent instrumental records are far from centennial- to millennial-scale averages. Hence, there is a need to establish longer sea-ice time series covering the present interglacial (Holocene; last 11,700 years) to test the full range of natural sea-ice variations and related environmental conditions. Moreover, although sea-ice development is especially important for Arctic ecosystems and society, our understanding of sea ice around Greenland is limited. While the modern sea-ice development is closely monitored, the inadequate knowledge of its historical development is detrimental to reliable model predictions. Thus, the objectives of the G-ICE project are to:

·         Define the baseline of Greenland sea-ice cover under pre-industrial climatic conditions.

·         Document the natural variability of sea ice around Greenland through time, at decadal to millennial scales beyond the instrumental period.

·         Identify natural trends, range of variations and extremes conditions, and test their relation to e.g. solar forcing, precipitation, bathymetry, ice-ocean heat exchange, and volcanic activity.

·         Evaluate the short- and long-term response of sea-ice cover and ocean circulation to Greenland ice-sheet melt.

·         Develop and test scenarios of sea ice and ocean conditions under a future “warm climate” from intervals marked by climate optima, such as the mid-Holocene and the medieval warm period.

Research plan and methodology. The science plan is organized around the development of multi-decadal to millennial-scale time series through the Holocene, with primary focus on the most recent millennia. This allows us to document the full range of natural sea-ice variability and its linkages with Greenland ice-sheet dynamics/melting, ocean circulation and global climate. Sea-ice variability time series will be established from sedimentary archives (cores) using multidisciplinary approaches for setting the chronological frame, estimating sea-ice extent and concentration and determining parameters (e.g., temperature, salinity, storminess, melting events) that influence sea-ice distribution. These records will be based on micropaleontological (foraminifera, diatoms, dinoflagellates), geochemical (biomarkers, elemental composition and stable isotopes) and sedimentological (grain size) proxies.

Project participants

Marit-Solveig Seidenkrantz

Christof Pearce

Henrieka Detlef

Katrine Elnegaard Hansen

Joanna Martin Davies

Former participants: Mimmi Oksman, Teodora Pados-Dibattista

Funding: the project is funded with DKK 5.469.606 from the Independent Research Fund Denmark for the period 2017-2021.