Pro: the Greenland Ice Melting Will Cause Disastrous Sea Level Rise.
From early 2003 to mid-2013, the total mass of ice in Greenland declined at a progressively increasing rate. In mid-2013, an abrupt reversal occurred, and very little net ice loss occurred in the next 12–18 months. Gravity Recovery and Climate Experiment (GRACE) and global positioning system (GPS) observations reveal that the spatial patterns of the sustained acceleration and the abrupt deceleration in mass loss are similar. The strongest accelerations tracked the phase of the North Atlantic Oscillation (NAO). The negative phase of the NAO enhances summertime warming and insolation while reducing snowfall, especially in west Greenland, driving surface mass balance (SMB) more negative, as illustrated using the regional climate model MAR. The spatial pattern of accelerating mass changes reflects the geography of NAO-driven shifts in atmospheric forcing and the ice sheet’s sensitivity to that forcing. We infer that southwest Greenland will become a major future contributor to sea level rise.https://www.pnas.org/content/116/6/1934
“Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than any time during the last three and a half centuries, if not thousands of years,” said Luke Trusel, a glaciologist at Rowan University’s School of Earth & Environment and former post-doctoral scholar at Woods Hole Oceanographic Institution, and lead author of the study. “And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s.”
“From a historical perspective, today’s melt rates are off the charts, and this study provides the evidence to prove this” said Sarah Das, a glaciologist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study. “We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20th century alone.”
Ice loss from Greenland is one of the key drivers of global sea level rise. Icebergs calving into the ocean from the edge of glaciers represent one component of water re-entering the ocean and raising sea levels. But more than half of the ice-sheet water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. The study suggests that if Greenland ice sheet melting continues at “unprecedented rates” — which the researchers attribute to warmer summers — it could accelerate the already fast pace of sea level rise.https://www.sciencedaily.com/releases/2018/12/181205133942.htm
Con: The Greenland Ice Sheet Melting Is Normal and Almost Undetectable.
Thirty years ago, the Greenland ice sheet was barely melting at all. “Six times” almost no ice loss remains almost no ice loss.
When recent ice loss is compared to the full Greenland ice sheet, the loss is so small that it is almost undetectable.
Sea-level measurements contradict claims that Greenland ice loss threatens coastal flooding. NASA satellite instruments, with readings dating back to 1993, show global sea level rising at a pace of merely 1.2 inches per decade, which is not significantly different than the typical rate of sea-level rise since the mid-1800s.
NASA scientists and media pundits have said this about the Greenland and Antarctic ice sheets: “The two regions have lost 6.4 trillion tons of ice in three decades; unabated, this rate of melting could cause flooding that affects hundreds of millions of people by 2100.” However, that is far short of even 1 percent of Greenland’s ice mass. As shown in the right graph in Figure 1, below, the total ice loss each year is a nearly undetectable five one-thousandths of one percent (0.005 percent) of the Greenland ice mass.
- Greenland, Antarctica Melting Six Times Faster Than in the 1990s source: NASA press release. Accessed 03/28/20 https://www.nasa.gov/feature/jpl/greenland-antarctica-melting-six-times-faster-than-in-the-1990s
- NASA satellite instruments, with readings dating back to 1993, show global sea level rising at a pace of merely 1.2 inches per decade. “Sea Level Rise,” Climate at a Glance, accessed 4/2/20, https://climateataglance.com/climate-at-a-glance-sea-level-rise/
- The data plotted in the graphs above is from the ice sheet mass balance inter-comparison exercise (IMBIE), a joint exercise by NASA and the European Space Agency. http://imbie.org/about-the-project/