Source: Global warming is causing rain to melt the Greenland ice sheet | John Abraham | Environment | The Guardian . . . A new study, just published in Nature Geoscience, makes an important new contribution to our understanding of the forces at play in Greenland. Dr Samuel Doyle and an international team captured the wide-scale effects of an unusual week of warm, wet weather in late August and early September, 2011. They found that cyclonic weather led to extreme surface runoff – a combination of ice melt and rain – that overwhelmed the ice sheet’s basal drainage system. This drive a marked increase in ice flow across the entire western sector of the ice sheet that extended 140 km into the ice sheet’s interior. According to Dr. Doyle, It wasn’t just rainfall. We saw 10 to 15% of the total annual surface melt occur in this event in late summer 2011. When this water reached the bed, the ice sheet lifted up and moved faster towards the sea. The cyclonic weather system delivered heat and rain to the western edge of the Greenland ice sheet and under these warm, wet, cloudy conditions the way that the ice sheet receives energy for melt is very different to that under the more typical clear sky conditions. . . . This makes a lot of sense. In effect, an overload of water from rain was enough to 'float' the ice sheet nearly 90 miles inland. Impressive! In effect, local rain over the Greenland ice sheet resulted in a flood, under the ice. Just like our traditional floods, they lift large objects and carry them down stream . . . towards the sea. Bob Wilson
Greenland Ice Sheet Today | Surface Melt Data presented by NSIDC hmm sounds normal for greenland melt
The article refers to a 2011 event when a late season, rain storm came in and overwhelmed the ice sheet drainage channels. Ordinarily polar precipitation is thought of as snow and blizzards but it had not occurred to me that a rapidly moving, warm-air, rain storm system might reach polar climates. So a day before, I saw this weather report: Source: Tuesday Claudette Update and My Thoughts on This Week - Canadian Weather Blog Weather Blog Now Newfoundland and Labrador are the last land masses before the Labrador Sea and Greenland. So Claudette is not going to repeat the 2011 event. Rather this paper gives a 'heads up' of what to look for. I've gotten used to seeing polar air masses arriving at lower latitudes leading to warm-air incursion over the Arctic and reduced or accelerated melting. In like fashion, the sustained, high pressure heat systems like the recent ones in North America and Europe, keeps the rate of ice melt lower. There is both correlation and causation. What is new is to keep a weather eye out for late-season, rain systems. We may go several years before another one comes along like the 2011 event. Also, look at the 2011 sea level data to see if this event is detectable. Bob Wilson
Sure and I just was posting another article with perspective. We don't really know if that just sped up release of the firn or increased melt rates (acceleration). .From your OP article Unfortunately the guardian piece included this Which is a great misunderstanding of the science here The confidence area of 0.3-1 meter includes a big fudge factor for mechanisms like this. This does nothing to move the yardstick, but simply points to an area of research. In fact I would say this study helps confirm that confidence range. To move the estimates you either need a big new contributor, or something exponential in nature. Certainly these mechanisms do more to load evidence against the hansen projection of 6 meters by 2100. The second misunderstanding in this conclusion is global sea level rise is the same as local. Many places will have sea level rises more than global, many less. Most areas less than 4 meters above sea level should be thought of at risk until individual risk assessments are done. That includes storm surges, and has nothing to do with this study, but does to sea level rise.
Which is a great lead in to one of my favorite satellite systems, the Jason series: Source: Sea Level Anomalies | NASA The reason this is important is the correlation with current sea surface temperatures: For me, a fascinating area. We may be seeing patterns of leading and trailing indicators, sea level and temperature. Bob Wilson
