Multiple‐stage deglacial retreat of the southern Greenland Ice Sheet linked with Irminger Current warm water transport

Abstract

There is limited knowledge pertaining to the history of the Greenland Ice Sheet (GIS) during the last glacial‐interglacial transition as it retreated from the continental margins to an inland position. Here we use multiproxy data, including ice‐rafted debris (IRD); planktonic isotopes; alkenone temperatures; and tephra geochemistry from the northern Labrador Sea, off southwest Greenland, to investigate the deglacial response of the GIS and evaluate its implications for the North Atlantic deglacial development. The results imply that the southern GIS retreated in three successive stages: (1) early deglaciation of the East Greenland margins, by tephra‐rich IRD that embrace Heinrich Event 1; (2) progressive retreat during Allerød culminating in major meltwater releases (δ18O depletion of 1.2‰) at the Allerød–Younger Dryas transition (12.8–13.0 kyr B.P.); and (3) a final stage of glacial recession during the early Holocene (∼9–11 kyr B.P.). Rather than indicating local temperatures of ambient surface water, the alkenones likely were transported to the core site by the Irminger Current. We attribute the timing of GIS retreat to the incursion of warm intermediate waters along the base of grounded glaciers and below floating ice shelves on the continental margin. The results lend support to the view that GIS meltwater presented a forcing factor for the Younger Dryas cooling.

The influence of meltwater on the Labrador Current in Heinrich event 1 and the Younger Dryas

“…However, distal freshwater release farther north, such as from Greenland, cannot be excluded. In the northmost Labrador Sea, Knutz et al (2011) observed two pulses of large oxygen isotope depletions with increased ice-rafted detritus before Younger Dryas event from Core DA04-31P within West Greenland Current (Fig. 7).…”

“…The meltwater trapped by the West Greenland Current might be also Rashid et al (2003). IRD abundance in core DA04-31P is redrawn from Knutz et al (2011).…”

The Greenland Ice Sheet during the last glacial cycle: Current ice loss and contribution to sea-level rise from a palaeoclimatic perspective

“…Other factors such as changing ocean currents (e.g. Knutz et al, 2011;Winsor et al, 2012) and internal ice-sheet dynamics (e.g. Joughin et al, 2001) may have played an important role for the difference in timing of initial ice-margin retreat between regions.…”

A 100-year long record of alkenone-derived SST changes by Southeast Greenland

“…Greenland Current system has been reported in the north eastern Labrador Sea during the last deglacial period by Knutz et al (2011).…”