Abstract
Arctic sea ice is a critical component of the climate system, known to influence ocean circulation, earth’s albedo, and ocean–atmosphere heat and gas exchange. Current developments in the use of IP25 (a sea ice proxy with 25 carbon atoms only synthesized by Arctic sea ice diatoms) have proven it to be a suitable proxy for paleo-sea ice reconstructions over hundreds of thousands to even millions of years. In the NE Baffin Bay, off NW Greenland, Melville Bugt is a climate-sensitive region characterized by strong seasonal sea ice variability and strong melt-water discharge from the Greenland Ice Sheet (GIS). Here, we present a centennial-scale resolution Holocene sea ice record, based on IP25 and open-water phytoplankton biomarkers (brassicasterol, dinosterol and HBI III) using core GeoB19927-3 (73° 35.26′ N, 58° 05.66′ W). Seasonal to ice-edge conditions near the core site are documented for most of the Holocene period with some significant variability. In the lower-most part, a cold interval characterized by extensive sea ice cover and very low local productivity is succeeded by an interval (~ 9.4–8.5 ka BP) with reduced sea ice cover, enhanced GIS spring melting, and strong influence of the West Greenland Current (WGC). From ~ 8.5 until ~ 7.8 ka BP, a cooling event is recorded by ice algae and phytoplankton biomarkers. They indicate an extended sea ice cover, possibly related to the opening of Nares Strait, which may have led to an increased influx of Polar Water into NE-Baffin Bay. The interval between ~ 7.8 and ~ 3.0 ka BP is characterized by generally reduced sea ice cover with millennial-scale variability of the (late winter/early spring) ice-edge limit, increased open-water conditions (polynya type), and a dominant WGC carrying warm waters at least as far as the Melville Bugt area. During the last ~ 3.0 ka BP, our biomarker records do not reflect the late Holocene ‘Neoglacial cooling’ observed elsewhere in the Northern Hemisphere, possibly due to the persistent influence of the WGC and interactions with the adjacent fjords. Peaks in HBI III at about ~ 2.1 and ~ 1.3 ka BP, interpreted as persistent ice-edge situations, might correlate with the Roman Warm Period (RWP) and Medieval Climate Anomaly (MCA), respectively, in-phase with the North Atlantic Oscillation (NAO) mode. When integrated with marine and terrestrial records from other circum-Baffin Bay areas (Disko Bay, the Canadian Arctic, the Labrador Sea), the Melville Bugt biomarker records point to close ties with high Arctic and Northern Hemispheric climate conditions, driven by solar and oceanic circulation forcings.
Highlights
Polar regions in the Northern Hemisphere, especially the Arctic and Greenland areas, are undergoing dramatic changes due to an accelerating reduction in sea ice cover and ice sheet extent for the past three–four decades
Organic geochemical and biomarker analyses of a well 14C-AMS- and 210Pb-dated sediment core from NE Baffin Bay show that major environmental and paleoceanographic changes occurred in this area
In the lower-most part, a cold interval characterized by extensive sea ice cover and very low local productivity is succeeded by an interval (~ 9.4–8.5 ka BP) of persistent, albeit strongly variable sea ice cover, enhanced Greenland Ice Sheet (GIS) spring melting, and strong influence of the West Greenland Current (WGC) in the earliest part of the record
Summary
Polar regions in the Northern Hemisphere, especially the Arctic and Greenland areas, are undergoing dramatic changes due to an accelerating reduction in sea ice cover and ice sheet extent for the past three–four decades. The summer sea ice extent and thickness of multi-year ice are decreasing at the fastest rate ever observed during recent times (− 8.6% per decade), and model simulations suggest that Arctic summer sea ice may. Given the magnitude of the ongoing reduction in the sea ice cover, information on its impact on water mass circulation and related natural climate conditions over longer time scales is important, notably for the testing of predictive climate models. The ongoing enhanced melting of the Greenland Ice Sheet (GIS), and its significant contribution (~ 0.34 mm year−1) [102] to global annual sea-level rise (~ 3.3 mm year−1) [23], needs to be appraised in relation to natural processes that occurred at millennial to centennial time scales during the present interglacial
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