Greenland Melt off to a Rather Early Start

Of the two great masses of land ice capable of dramatically raising sea levels and altering hemispheric weather patterns through global warming spurred melt, Greenland is the one closest to home for many humans living on Earth. And as fossil fuel burning keeps dumping more carbon into our atmosphere, Greenland melt continues to dump tens of billions of tons of water into the world’s oceans each year.

Greenland melt extent 2019

(Early bump in Greenland melt may be a blip — or a presage to another above average surface melt during summer. Image source: NSIDC.)

At present, Greenland contributes approximately 280 billion tons of water to global sea level rise through melt and mass loss per annum. And as the Earth warms, the potential for Greenland to spill still more into the North Atlantic is a rising concern.

So each spring through summer, we go through a ritual of anxiously monitoring the Greenland ice sheet for surface melt increases. Such monitoring is not without merit. According to recent reports in Nature, approximately 60 percent of mass loss in Greenland is driven by surface warming and melt. And during 2012, a major warming event resulted in practically all of the Greenland ice sheet experiencing surface melt during summer.

(Since surface mass loss is the primary driver of Greenland melt, the summer season is a big deal for the Northern Hemisphere’s largest cache of land ice.)

We haven’t had another melt year like 2012 in the intervening time through today. But we have seen continued net mass loss from Greenland — with the additional 40 percent coming from melt due to contact with warming oceans. In other words, we’re experiencing Greenland melt both at the surface and from below. And, sooner or later, so long as fossil fuel burning keeps dumping greenhouse gasses into Earth’s atmosphere, we’ll see another summer like 2012. Or worse.

So we watch.

For the present year, Greenland surface melt has gotten off to a relatively strong and early start. Melt extent jumped to around 7 percent in early May. A pace well beyond the top 10 percent of recorded melt years for the period in which the spike occurred. And it may presage another summer of ponding spreading across the face of Greenland. But the present mid-May bump is not a fully reliable indicator — as 2017’s melt progression featuring a strong start with a relatively moderate and late peak shows.

For further comparison, we saw some rather strong early melt spikes in March and April of 2012 prior to that record surface melt year. And during 2018, which was only a somewhat above average (1981-2010) melt year, there were practically no melt spikes during March through late May.

A primary driver for surface melt during the present years of record and rising global heat has been the formation of jet stream ridges and strong upper level high pressure systems over Greenland during spring and summer. To point, this year’s recent melt spike coincided with a strong ridge that locked into place during mid April through early May.

Over the next ten days, the atmosphere above Greenland is predicted to fluctuate as highs and lows progress. Temperatures are expected to remain somewhat above average near the surface of the ice mass. Compared to the stronger signal we saw earlier, the indicators here are somewhat mixed — at least for the next ten days. But if the ridge pattern reasserts from late May and on into June — watch out. Then, we could see another big melt spike coinciding with the onset of summer.

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