There are many Antarctic interactions with, and lessons to be learned from, Greenland that are not fully discussed in the Greenland folder, therefore, I am opening this new folder on this important topic.
In the "Surge" thread I raised the prospect that the large increase in Greenland's contribution to SLR in 2012 might have triggered a temporarily large outflow of subglacial meltwater from beneath the WAIS via a postulated increase in local sea level around West Antarctic (due to the fingerprint effect of ice mass loss from Greenland), temporarily lifting up the grounding lines of key West Antarctic glaciers, thereby temporarily breaking the seal and allowing the basal melt water to surge out (and to also temporarily increase ice flow velocity). While the "Surge" thread does document small surges of the Thwaites, and Ferrigano, Ice Tongues; the subsequent published GRACE data indicated that at best there was only a very minor surge in WAIS ice mass loss in 2012.
Nevertheless, the 2012 experience does not mean that the postulated interaction between Greenland and AIS mass loss many not be more significant in the next few decades, as not only is Greenland's surface ice mass loss projected to increase in the near future, but as indicated by the following article, which discusses dynamic ice mass loss for four key marine terminating Greenland glaciers; which are projected to accelerate sharply in the next few decades before slowing down through 2200. Therefore, there is a reason likelihood that the projected temporary surge in Greenland ice mass loss in the coming decades could trigger an acceleration of ice mass loss from key glaciers in the AIS (particularly in the WAIS):
http://www.nature.com/nature/journal/v497/n7448/full/nature12068.htmlFuture sea-level rise from Greenland’s main outlet glaciers in a warming climateby: Faezeh M. Nick, Andreas Vieli, Morten Langer Andersen, Ian Joughin, Antony Payne, Tamsin L. Edwards, Frank Pattyn & Roderik S. W. van de Wal; Nature; 497,235–238(09 May 2013)doi:10.1038/nature12068
"Over the past decade, ice loss from the Greenland Ice Sheet increased as a result of both increased surface melting and ice discharge to the ocean. The latter is controlled by the acceleration of ice flow and subsequent thinning of fast-flowing marine-terminating outlet glaciers. Quantifying the future dynamic contribution of such glaciers to sea-level rise (SLR) remains a major challenge because outlet glacier dynamics are poorly understood. Here we present a glacier flow model that includes a fully dynamic treatment of marine termini. We use this model to simulate behaviour of four major marine-terminating outlet glaciers, which collectively drain about 22 per cent of the Greenland Ice Sheet. Using atmospheric and oceanic forcing from a mid-range future warming scenario that predicts warming by 2.8 degrees Celsius by 2100, we project a contribution of 19 to 30 millimetres to SLR from these glaciers by 2200. This contribution is largely (80 per cent) dynamic in origin and is caused by several episodic retreats past overdeepenings in outlet glacier troughs. After initial increases, however, dynamic losses from these four outlets remain relatively constant and contribute to SLR individually at rates of about 0.01 to 0.06 millimetres per year. These rates correspond to ice fluxes that are less than twice those of the late 1990s, well below previous upper bounds. For a more extreme future warming scenario (warming by 4.5 degrees Celsius by 2100), the projected losses increase by more than 50 per cent, producing a cumulative SLR of 29 to 49 millimetres by 2200."
This hypothesis is further supported by the recent finding (see the following reference) that the lithosphere below Greenland is thinner than previously thought; and therefore, one can expect that ice mass loss from Greenland will be faster than previously estimated (including faster than projected by the first article cited in this post):
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1898.htmlPetrunin, A. G., Rogozhina, I., Vaughan, A. P. M., Kukkonen, I. T., Kaban, M. K., Koulakov, I. & Thomas, M.,
Heat flux variations beneath central Greenland’s ice due to anomalously thin lithosphere, Advance Online Publication, Nature Geoscience, 11. 08. 2013,
http://dx.doi.org/10.1038/ngeo1898)
"Greenland ice is melting - even from below: Heat flow from the mantle contributes to the ice melt. Modeled basal ice temperatures of the present-day Greenland Ice Shield across the Summit region, GRIP and GISP2 indicate borehole locations.
07.08.2013 | Potsdam: The Greenland ice sheet is melting from below, caused by a high heat flow from the mantle into the lithosphere. This influence is very variable spatially and has its origin in an exceptionally thin lithosphere. Consequently, there is an increased heat flow from the mantle and a complex interplay between this geothermal heating and the Greenland ice sheet. The international research initiative IceGeoHeat led by the GFZ German Research Centre for Geosciences establishes in the current online issue of Nature Geosciences (Vol 6, August 11, 2013) that this effect cannot be neglected when modeling the ice sheet as part of a climate study.
The continental ice sheets play a central role in climate. Interactions and feedback processes between ice and temperature rise are complex and still a current research topic. The Greenland ice sheet loses about 227 gigatonnes of ice per year and contributes about 0.7 millimeters to the currently observed mean sea level change of about 3 mm per year. Existing model calculations, however, were based on a consideration of the ice cap and considered the effect of the lithosphere, i.e. the earth's crust and upper mantle, too simplistic and primarily mechanical: the ice presses the crust down due to its weight. GFZ scientists Alexey Petrunin and Irina Rogozhina have now coupled an ice/climate model with a thermo-mechanical model for the Greenland lithosphere. "We have run the model over a simulated period of three million years, and taken into account measurements from ice cores and independent magnetic and seismic data", says Petrunin. "Our model calculations are in good agreement with the measurements. Both the thickness of the ice sheet as well as the temperature at its base are depicted very accurately. "
The model can even explain the difference in temperature measured at two adjacent drill holes: the thickness of the Greenland lithosphere and thus the geothermal heat flow varies greatly in narrow confines.
What does this mean for climate modeling? "The temperature at the base of the ice, and therefore the current dynamics of the Greenland ice sheet is the result of the interaction between the heat flow from the earth's interior and the temperature changes associated with glacial cycles," explains corresponding author Irina Rogozhina (GFZ) who initiated IceGeoHeat. "We found areas where the ice melts at the base next to other areas where the base is extremely cold."
The current climate is influenced by processes that go far back into the history of Earth: the Greenland lithosphere is 2.8 to 1.7 billion years old and is only about 70 to 80 kilometers thick under Central Greenland. It remains to be explored why it is so exceptionally thin. It turns out, however, that the coupling of models of ice dynamics with thermo-mechanical models of the solid earth allows a more accurate view of the processes that are melting the Greenland ice."
