Ice has been melting from Greenland and Antarctdica’s glaciers at a rate six times greater than 20 or 30 years ago. According to NASA, “If the current melting trend continues, the regions will be on track to match the “worst-case” scenario of the Intergovernmental Panel on Climate Change (IPCC) of an extra 6.7 inches (17 centimeters) of sea level rise by 2100.”
Keep in mind two things, when you read this 6.7 inch statistic. 1) Historically, the most hand-wringing, pearl clutching ice melt experts underestimate the rate of melting. That trend has been consistent for two decades. 2) When talking about both Greenland and Antarctica, if Greenland is a big deal, but if Greenland is big, Antarctica is Humongous. Greenland experiences, melty summers and snowy winters, so there is a regular flux of ice mass, with the trend being net loss over time in recent years. Antarctica experiences below freezing temperatures even in the summer over most of its ice mass. Well, until recently. Recently, there have been daytime temperatures sufficient to melt the surface.
In all, the Greenland Ice Sheet has enough water to raise global sea levels by 7.4 meters, if it all melted. From the article in nature:
Over recent decades, ice losses from Greenland have made a substantial contribution to global sea-level rise, and model projections suggest that this imbalance will continue in a warming climate… [Recent research has shown a] five fold increase in the rate of ice loss from Greenland overall, rising from 51 ± 65 Gt yr?1 in the early 1990s to 263 ± 30 Gt yr?1 between 2005 and 2010. … There was, however, a marked reduction in ice loss between 2013 and 2018, as a consequence of cooler atmospheric conditions and increased precipitation. Although the broad pattern of change across Greenland is one of ice loss, there is considerable variability; for example, during the 2000s just four glaciers were responsible for half of the total ice loss due to increased discharge, whereas many others contribute today. Moreover, some neighbouring ice streams have been observed to speed up over this period while others slowed down, suggesting diverse reasons for the changes that have taken place—including their geometrical configuration and basal conditions, as well as the forcing they have experienced. In this study we combine satellite altimetry, gravimetry and ice velocity measurements to produce a reconciled estimate of the Greenland Ice Sheet mass balance between 1992 and 2018, we evaluate the impact of changes in SMB and uncertainty in glacial isostatic adjustment and we partition the ice sheet mass loss into signals associated with surface mass balance and ice dynamics. In doing so, we extend a previous assessment to include more satellite and ancillary data and to cover the period since 2012.
The result of this melting has been .7 inches of sea level rise, or a third of all sea level rise, during the study period.
Previusly, the IPCC estimated that global sea levels would rise about 28 inches by 2100. That is enough to remove Cape Hatteras and possibly require New York City to build dikes or move to avoid flooding in much of its area. But, the IPCC gave a range of possible scenarios, and this study suggests that the worst of those is well within the range of possibility.
HERE is the link to the research team’s site.
Source: The IMBIE Team. 2019/2020 (first early publication Dec 10 2019, published in March 12 2020 issue). Mass blanance of the Greenland Ice Sheet from 1992 to 2018. Nature 579, 233-239(2020)