Threatened loss of the Greenland Ice Sheet

Centre for Global Atmospheric Modelling, Department of Meteorology, University of Reading, Reading RG6 6BB, UK.
Nature (Impact Factor: 41.46). 05/2004; 428(6983):616. DOI: 10.1038/428616a
Source: PubMed


The Greenland ice-sheet would melt faster in a warmer climate and is likely to be eliminated--except for residual glaciers in the mountains--if the annual average temperature in Greenland increases by more than about 3 degrees C. This could raise the global average sea-level by 7 metres over a period of 1,000 years or more. We show here that concentrations of greenhouse gases will probably have reached levels before the year 2100 that are sufficient to raise the temperature past this warming threshold.

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Available from: Philippe Huybrechts
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    • "This topographic relief, together with the high surface albedo, generates a cold interior and consequently has a relevant thermodynamical impact on transient air masses. The Greenland ice sheet represents also a freshwater reservoir equivalent to a global sea level rise of 7 m [Gregory et al., 2004]. "
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    ABSTRACT: We show that the absence of the Greenland ice sheet would have important consequences on the North Atlantic Ocean circulation, even without taking into account the effect of the freshwater input to the ocean from ice melting. These effects are investigated in a 600-year long coupled ocean–atmosphere simulation with the high-resolution global climate model EC-Earth 3.0.1. Once a new equilibrium is established, a cooling of Eurasia and of the North Atlantic and a poleward shift of the subtropical jet are observed. These hemispheric changes are ascribed to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) by about 12%. We attribute this slowdown to a reduction in salinity of the Arctic basin and to the related change of the mass and salt transport through the Fram Strait – a consequence of the new surface wind pattern over the lower orography. This idealized experiment illustrates the sensitivity of the AMOC to local surface winds.
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    • "Inset (adapted from Vaughan et al., 2013) shows the ice loss determined between 2006 and 2012 from GRACE time-variable gravity data in cm water/year from the East and West Antarctic Ice Sheets (EAIS and WAIS respectively). land Ice Sheet is quite vulnerable to warming climate (Gregory et al., 2004), at least some studies (Huybrechts and de Wolde, 1999) predict that the EAIS will grow owing to increased precipitation (see also Alley et al., 2005). Worryingly, recent reports indicate that while parts of the EAIS are growing, other parts are decreasing (Fig. 1 and Vaughan et al., 2013). "
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    ABSTRACT: IODP Expedition 318 drilled Site U1361 on the continental rise offshore of Adélie Land and the Wilkes subglacial basin. The objective was to reconstruct the stability of the East Antarctic Ice Sheet (EAIS) during Neogene warm periods, such as the late Miocene and the early Pliocene. The sedimentary record tells a complex story of compaction, and erosion (thus hiatuses). Teasing out the paleoenvironmental implications is essential for understanding the evolution of the EAIS. Anisotropy of magnetic susceptibility (AMS) is sensitive to differential compaction and other rock magnetic parameters like isothermal remanence and anhysteretic remanence are very sensitive to changes in the terrestrial source region. In general, highly anisotropic layers correspond with laminated clay-rich units, while more isotropic layers are bioturbated and have less clay. Layers enriched in diatoms are associated with the latter, which also have higher Ba/Al ratios consistent with higher productivity. Higher anisotropy layers have lower porosity and moisture contents and have fine grained magnetic mineralogy dominated by maghemite, the more oxidized form of iron oxide, while the lower anisotropy layers have magnetic mineralogies dominated by magnetite. The different magnetic mineralogies support the suggestion based on isotopic signatures by Cook et al. (2013) of different source regions during low productivity (cooler) and high productivity (warmer) times. These two facies were tied to the coastal outcrops of the Lower Paleozoic granitic terranes and the Ferrar Large Igneous Province in the more inland Wilkes Subglacial Basin respectively. Here we present evidence for a third geological unit, one eroded at the boundaries between the high and low clay zone with a “hard” (mostly hematite) dominated magnetic mineralogy. This unit likely outcrops in the Wilkes subglacial basin and could be hydrothermally altered Beacon sandstone similar to that detected by Craw and Findlay (1984) in Taylor Valley or the equivalent to the Elatina Formation in the Adelaide Geosyncline in Southern Australia (Schmidt and Williams, 2013). Correlation of the “hard” events with global oxygen isotope stacks of Zachos et al. (2001) and Lisiecki and Raymo (2005) suggest that the source region was eroded during times with higher global ice volume.
    Full-text · Article · Feb 2015 · Earth and Planetary Science Letters
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    • "This dynamic retreat through increased rates of ice flow could happen much faster than could be achieved by melting of the ice in situ. Thus, the resulting rise in sea level could be much faster than for example the loss of the Greenland ice sheet, which would require melting of the ice, taking many hundreds or even thousands of years (Gregory et al., 2004; Lowe et al., 2005). Although people often speak about a ''WAIS collapse'', meaning the loss of most or all of the WAIS landbased ice, this process would in fact be slower that collapse might imply. "

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