A paper from a paleoclimatology workshop finds that the southern dome of Greenland did not melt away during the extreme natural climate change of the "Eemian interglacial (125,000 years ago), when annual mean temperatures over Greenland were [about] 5°C warmer than now for some millenia [thousands of years]." The author asks, "will [the southern dome of Greenland] melt away for the first time in 400,000 years?" and concludes, "Probably not." The IPCC claims [non-existent] positive feedback from water vapor could lead to 3°C warming from doubled CO2 levels, but lessons from the geological past show that even if the globe warmed 2°C more to 5°C warmer than the present for thousands of years, neither the northern nor southern domes of Greenland would melt away.
Will we lose the southern dome? - the lesson from the geological past
Svend Funder, University of Copenhagen
Abstract: Recent years’ rapid melting of the Greenland ice sheet has shown that the southern dome is the ice sheet’s most vulnerable part. The southern ice sheet dome, the area south of c. 67°N, is a highland ice cap with its base c. 500 m a.s.l. It contains c. 15% of the Greenland ice sheet’s volume, equal to c. 1 m global sea level, and is characterised by very high accumulation and melting. Two of the most active outlets from the ice sheet, Jakobshavn Isbræ and Helheim Gletscher drain the saddle between the northern and southern ice sheet domes.
Can the southern dome’s response to past warming give us a clue to its fate in the future? ODP borings on the shelf have shown that the ice dome has existed, on and off, at least since the Miocene. Recent results from the DYE 3 ice core and other sources indicate that the dome melted away, and gave way to forested mountains for the last time during marine isotope stage 11, c. 400,000 years ago. The southern dome, and of course the northern also, persisted in a reduced form during the warm Eemian interglacial (c. 125,000 years ago), when annual mean temperatures over Greenland were c. 5°C warmer than now for some millenia. During the last ice age the southeast coast of Greenland was one of the areas of major ice sheet growth, reaching the shelf edge at the last glacial maximum, c. 20,000 years ago, as shown by bathymetric studies. During the Holocene thermal maximum, c. 8,000 years ago, when annual mean temperatures were c. 2°C warmer than now for some thousands of years, modelling and GPS altimetry show that the southern dome was the most sensitive part of the ice sheet, retreating as much as 80 km behind its present front in some areas. After this, during the neoglacial the ice margin readvanced. In spite of the large scale changes in ice cover in this area, the Holocene isostatic history is peculiarly muted and characterised by low uplift. This can be interpreted in several ways, but does show an abnormal ice load history, when compared to other sectors of the ice sheet.
In general, the variable behaviour of the southern dome through the geological record contrasts with that of the much more resilient northern dome. Judged from this, we can expect a more direct and vigorous response to warming in the southern dome than in the much larger northern dome, but will it melt away for the first time in 400,000 years? – Probably not.