Ice Retreat Forcings in Southwest Greenland from the Last Glacial Maximum through the Late Holocene

Abstract:

As climate warms and ice margin positions recede, Greenland ice retreat is driven by changing forcings. With a focus on southwest Greenland, we review the current understanding of these retreat drivers from the end of the last glaciation through the late Holocene. Shortly after the glacial maximum, ice margins withdrew rapidly from the continental shelf break, responding to small increases in insolation and/or eustatic sea level. For the next several thousand years, little net margin migration is observed. Then, just prior to the start of the Holocene, the southwestern Greenland ice sheet retreated onto the modern coastline. There, marine-terminating outlet glaciers thinned and retreated more quickly than did land-based ice. At the same time, the Labrador Sea experienced warming that led into its early Holocene maximum temperatures. This suggests that the rapid retreat of marine-terminating outlet glaciers was driven by a warming ocean. Transitioning into the early Holocene, southwest Greenland ice margins responded to relatively strong radiative forcing and withdrew inside their present-day positions. After a subsequent advance during the mid- to late-Holocene Neoglacial, outlet glaciers retreated at different times over a ~2,000 year period. In some instances, this retreat was forced by warming after the Little Ice Age (LIA). In other cases, retreat may have been driven by local topography and/or local, pre-LIA climate changes. While questions remain, the magnitude of past southwest Greenland ice response to different retreat forcings can inform our projections of future retreat.