Rapid response of Arctic land ice during Dansgaard-Oeschger events and variation in water exchange between the Atlantic and Arctic oceans
Monday, 15 December 2014
The climate of the last glaciation was interrupted by numerous abrupt millennial scale temperature fluctuations between cold stadials and warm interstadials, the so-called Greenland Dansgaard-Oeschger events. During the warm interstadials the Atlantic Meridional Overturning Circulation (AMOC) was active and warm water flowed north into the Nordic seas. During the cold stadials the northern oceans were partially ice covered and the AMOC disrupted. So far, very little is known of changes in the surrounding ice sheets and in the discharge of meltwater in response to abrupt warmings even though variation in meltwater production is regarded to be a major factor in the instability. Here we present results from sediment cores from the western slope of Svalbard in order to reconstruct the delivery of sediments and meltwater from the archipelago as in response to stadial/interstadial shifts during MIS 3. During interstadials the normal greenish silt was replaced by laminated, pink clay originating from Devonian Red Beds on Svalbard and transported in suspension by meltwater to the coring site. The large distance from the ice margin to the site indicates the outpourings of meltwater were substantial, probably comparable to some of the largest outbursts during the deglaciation. The concentration of ice rafted debris decreased as the meltwater production increased signifying that the ice margin retreated from the coastal area. In the study, we establish the precise chronology for eight major meltwater discharges during MIS 3 corresponding to Dansgaard-Oeschger warmings DO-11 to DO-3. The results are based on the Svalbard-Barents Sea ice sheet, but it is likely that the Scandinavian ice sheet reacted concurrently. Our observations indicate that the Eurasian ice sheet was much more dynamic than previously recognized with retreat and advances closely linked to the Greenland interstadials and stadials .Our findings also provide clear evidence of a significant northern component to the rapid global sea-level changes that several lines of evidence suggest occurred during MIS 3. The results also show that the Dansgaard-Oeschger events strongly affected the water exchange in the Fram Strait between the Nordic seas and the Arctic Ocean.