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Transient regional warming has less impact on higher portions of the GrIS surface than on lower portions. The high mountains that dam the ice sheet in central east Greenland ensure that there is very little low surface ice per unit distance along the general trend of this ice margin, in comparison with the adjacent margins to the north and south Fig. This largely explains the near zero mean mass acceleration rates we inferred for east Greenland Fig.

Massachusetts Advance Sheet April 2013

In summary, we suggest that both the geographical distribution of the progressive summertime warming before , which was mostly focused in the west of Greenland, and the spatial structure of ice sheet sensitivity to atmospheric forcing, which is dominated by ice sheet topography near its margins, jointly explain most of the spatial pattern of SMB trend Fig.

This interpretation is supported by the recent history of runoff within the Taseriaq basin of southwest Greenland Both changes affect calving rates and the velocity of outlet glaciers, and cause inland changes in ice thickness. The secondary negative mass acceleration peak in northeast Greenland Fig.

The observation that the mass anomaly field Fig. All three GNET stations close to the GrIS margin in northeast Greenland recorded accelerating uplift from their date of installation through 12 , and they all recorded negative uplift anomalies after mid SI Appendix , Fig.

This reversal occurred rather later than There are at least two possible mechanisms: i regional warming drove a reduction in the extent of the floating ice sheet before the summer of , which diminished its buttressing effect on the outlet glaciers, prompting increased rates of discharge which thinned the ice, as observed in the Antarctic Peninsula 22 , 23 , and ii increases in meltwater production can modulate dynamical changes in ice mass. The northeast margin of the GrIS has a much greater area of low elevation surface than the margin sectors on either side Fig.

Increased surface melting lowers the viscosity of the ice sheet via the advection of latent heat to its interior 24 , and this mechanism will be volumetrically concentrated in thinner portions of ice sheet associated with low surface elevations. In extreme cases, the development of subglacial lakes can lift portions of an ice sheet or an ice cap from its bed 28 , The hypothesis that atmospheric warming can promote increases in discharge, dynamic thinning, and glacial retreat has recently been invoked in Prudhoe Land in northwest Greenland The coverage and quality of our meteorological, glaciological, and geodetic datasets decline as we regress to the mids, as does our ability to track the relative importance of SMB and DMB as drivers of deglaciation.

Even so, it is clear that the sustained acceleration in mass loss recorded by GRACE before mid was completely unprecedented 31 , as was the collapse of seasonally adjusted mass rate from its peak value to nearly zero in the following 12—18 mo. The pronounced negative shift in spatially integrated SMB Fig.

S8 was dominated by increased summertime runoff Fig. Runoff increased over most of the flanks of the GrIS, but most noticeably in southwest Greenland, where the margin was gaining mass in but strongly losing mass by late Fig. Total glacial discharge integrated over southwest Greenland is not only very low 9.

Similar considerations apply in southeast Greenland The decadal acceleration in mass loss in southwest Greenland arose due to the combination of sustained global warming and positive fluctuations in temperature and insolation driven by the NAO. Since , the NAO has worked in concert with global warming to trigger major increases in summertime runoff. Before , the air was too cool for the NAO to do the same. In a decade or two, global warming will be able to drive levels of runoff with little or no assistance from the NAO.

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In the shorter term, we can infer that the next time NAO turns strongly negative, SMB will trend strongly negative over west and especially southwest Greenland, just as future warming of the shallow ocean is expected to have its largest impact, via DMB 33 , 34 , in southeast and northwest Greenland. Because ice sheet topography equips southwest Greenland with greater sensitivity to atmospheric forcing, we infer that within two decades this part of the GrIS will become a major contributor to sea level rise.

There is also the suggestion that enhanced summertime melting may induce more sustained increases in discharge rates. Our GPS data processing followed that of ref. Further details, and a discussion of data access, can be found in SI Appendix. We are grateful to two anonymous reviewers for their comments and suggestions.

Author contributions: M. This article contains supporting information online at www. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address. Skip to main content. Michael Bevis. Significance The recent deglaciation of Greenland is a response to both oceanic and atmospheric forcings. Abstract From early to mid, the total mass of ice in Greenland declined at a progressively increasing rate. Discussion The coverage and quality of our meteorological, glaciological, and geodetic datasets decline as we regress to the mids, as does our ability to track the relative importance of SMB and DMB as drivers of deglaciation.

The authors declare no conflict of interest. Nature : — Geophys Res Lett 37 : L OpenUrl CrossRef. Wouters B , et al. Rep Prog Phys 77 : OpenUrl PubMed.

Van den Broeke MR , et al. Cryosphere 10 : — Bevis M , Brown A Trajectory models and reference frames for crustal motion geodesy. J Geod 88 : — Chen X , et al. Nat Clim Change 7 : — Bevis M , et al. Nielsen K , et al. Earth Planet Sci Lett : — J Geophys Res : 1 — 8. Khan SA , et al. Sci Adv 2 : e Khan A , et al.

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Nat Clim Change 4 : — Van Angelen J , et al. Surv Geophys 35 : — Fettweis X , et al. Cryosphere 7 : — Cryosphere 11 : — Brathwaite R Positive degree-day factors for ablation on the Greenland ice sheet studied by energy-balance modeling. Right now the inventory is 30,, Giga-tonnes which means it would take another 10, years to melt all the ice. But yes, Greenland would take around 10, years if melting continued.. AndyG55, Thanks for pointing out the schoolboy howler.

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When quoting numbers from memory I tend to drop a decimal point or two. This time my memory was good but my arithmetic was not. Why would anyone want an iced-over island or continent anyway? Seriously what would be the problem in water rising by 76 meters if all of Antarctica melted. Yeah, coastal city dwellers would have to move.

Heather J. Van Meter

Cry me a river. I thought progressives were for change? In most countries old contracts remain, but change of ownership becomes very difficult. That is a problem, because those houses are mostly investments also. You also can nor relocate these people, because their houses have a huge value, including a future premium added which of course does not factor in damage or loss to a massive storm. They obviously are not concerned with the tiny, almost imperceptible and immeasurable rate of sea level rise.

And that is, what i replied to. A problem turns up sea level. So for once please stick to the topic: you simply have to demonstrate that 76 m of sea level rise would not be a problem. Have fun! Of course 76 meters of sea level rise would be a problem over the next couple hundred years, but not over thousands of years. Indeed there are no signs of man-made polar melting whatsoever. Just because Greenland is fluctuating a couple of tenths of a percent, it is very well within natural variability limits, and so is the Arctic sea ice cover when examined over the past years, or when it is compared to the cover seen during the MWP, or other warm periods throughout the Holocene.

Unfortunately you have become a victim of hysteria spread by some nutty irresponsible alarmists — who are hopefully about to get the boot once Trump takes office. We all know that the AGW scammers have to invent and play with impossible hypotheticals that are never going to happen.

For sop, that would entail regular visits to a psychiatrist.. His anxiety symptoms seem to be deep and irreversible. There is a sop there pretending to be a climate scientist with an oil company. That corresponds to 80 mm of sea level rise per century. Your insurance company argument is absurd. My guess is that sea level will start falling in less than 5, years……it will be a real problem when the Laurentide glacier buries New York under 1, meter of ice. How will insurance companies cope with that? There has ben no acceleration in sea level rise, and there has been no warming in the whole satellite temperature era apart from El Nino events, which are actually ocean cooling events.