Monday, 18 January 2016

A Massive Greenland Melt Event in Winter

Did a January Hurricane Just Set off a Massive Greenland Melt Event in Winter?

18 January, 2015

We’ve seen unprecedented above-freezing temperatures at the North Pole coincident with record low daily sea ice extents. We’ve seen global temperatures hitting new, very extreme record highs. We’ve seen climate change related storms raging across the globe — flooding both the UK and the Central US, firing off record hurricanes during January in both the Pacific and the Atlantic — even as other regions swelter under record heat and drought.

(The remnants of hurricane Alex being pulled into a storm system just south of Greenland on Friday January 15, 2016. An event that then flooded both Baffin Bay and Western Greenland with warm, tropical air. At the same time, Greenland observers both noted what appears to be ice mass losses over Western Greenland as well as a possible large melt water outflow issuing from the Disko Bay area. Image source: Earth Nullschool.)

Greenland Melt During Winter

Greenland — the last bastion of major continental glacial ice in the Northern Hemisphere. An island archipelago dwarfed by great mountains of frozen water towering as high as two miles. Though the Arctic sea ice provides quite extensive coverage — in the range of millions of square miles — the great Greenland Ice Sheet contains the majority of the remaining frozen fresh water in the Northern Hemisphere. And though the extreme ongoing sea ice melt does not contribute to sea level rise, Greenland melt is another matter entirely. In total, if all of the Greenland Ice Sheet flooded into the world ocean, it would raise global sea levels by an average of 23 feet. Enough to inundate pretty much every coastal city in the world.
And Greenland is melting, pushing those sea levels higher. Contributing hundreds of cubic kilometers of melt water into the world ocean system every year since at least the middle of the first decade of the 21st Century. Creating an ominous ocean heat-conveyer that spreads fresh, cool water out at the surface even as it pulls deep, warmer water directly in toward the many glaciers whose towering faces plunge into the ocean itself.
During recent years, most of Greenland’s melt has occurred during the hot season of summer even as the ice sheet underwent re-freeze and a pseudo-recovery during Winter. Sure, net mass loss was in the range of hundreds of billions of tons each year. But we still had consistent and uninterrupted mass gain during Winter.
Unfortunately, with human-forced warming there was always a danger that, during Wintertime, we’d see an increase in melt pressure as well. At issue is the way in which greenhouse gasses fundamentally warm the atmosphere and oceans. Possessing the ability to re-radiate solar energy, greenhouse gasses have a greater impact on temperatures during times of darkness and during Winter. In other words, we’d expect nighttime temperatures to warm faster than daytime temperatures and we’d expect wintertime temperatures to warm faster than summertime temperatures. Perhaps more ominously, the oceans are very efficient holders of heat and are less impacted by seasonal variance than the lands. In other words, if the world’s oceans warm, they re-radiate much more heat back to the atmosphere and ice sheet during Winter than they do during Summer.
This kind of greenhouse gas warming is an assault on the winter season itself. It’s something we’ve seen in the frequent extreme polar warming episodes during recent years. One that this year generated a very odd and ominous period of above-freezing temperatures at the North Pole. But if there’s something even more odd than temperatures at the North Pole hitting above freezing during Winter, it’s an incident of substantial melt occurring over the Greenland ice sheets during what should be the coldest, darkest season.
January Hurricane Blows a Tropical Wind into the Arctic

Over the past few days, just such a major heat-up has been underway across a large section of Western Greenland. Warm winds flowing off the North Atlantic — driven by hurricane Alex’s merging with powerful lows south of Greenland — have roared up over the southern coastal ranges. Meanwhile, warm, tropical air has infiltrated northward over Baffin Bay. The net result is temperatures approaching 20-40 degrees Fahrenheit above average (16 to 22 C above average) over a broad region of Western Greenland.
Greenland Warm Up
Greenland warm up temperature
(By Sunday, 15-36 F above average temperatures had come to dominate much of southern and western Greenland. This translated to near or above freezing temperatures over sections of the Jacobshavn Glacier. Image source: Climate Reanalyzer.)

Over the past few days, as indicated in this recent post by Jason Box, the region near Disko and Uummannaq Bays — both in Baffin Bay and along the coastal ranges — has felt the full force of this substantial warm-up. By today, a large section of the coastal offshore waters and a wedge of glacier-covered Western Greenland all experienced near or above-freezing temperatures. A very rare event for Greenland and Baffin Bay during wintertime and one that appears to have coincided with a possible large glacial melt water outflow from the Jackobshavn Glacier.

Spot temperature readings along the southern reaches of the Jacobshavn Glacier hit 1 C or 34 F today according to GFS measures. Meanwhile near freezing temperatures have dominated Niaqornat on Uummannaq Bay (forecast to hit 32 F on Tuesday). Ilulissat on Disko Bay is showing 36 F temperatures at 12:00 AM Monday and is forecast to hit 41 F on Tuesday, even as Nuuk (about 200 miles south of Ilulissat) is showing 40 F temperatures at 12:00 AM Monday. These are all extremely warm readings for Greenland during Winter.
Greenland Glacial Melt During Winter

Disko and Uummannaq Bays are notable in that they are the outflow zone of the Jackobshavn Glacier — one of the swiftest-melting glaciers on Greenland. Over recent years, it has been one of the primary hot-spots for summer Greenland ice mass loss. But during recent days, mass loss also appears to have occurred in this area.
Western Greenland Melting in January
(Western Greenland has shown surface mass losses during recent days as in this January 17 mass balance data provided by DMI.)

Dr Jason Box notes that surface mass balance totals have consistently shown up as negative over the past week in the DMI measure. A record that continued today. Though Dr. Box states that such a negative mass balance could simply be chalked up to wintertime sublimation, the consistent losses showing up in the monitor over the past seven days have coincided temperatures in a melt-inducing range.

In addition, Dr Box also indicates a disturbing flushing of ice away from both Disko and Uummannaq Bays occurring on January 16th. In the satellite shot, both sea ice and ice burgs are moved en-mass from the bays and on out into the waters of Baffin.
Large Melt Water Pulse From Jacobshavn?

Offshore winds could be the cause. But, again, the ice movement coincides with indications of mass loss over Greenland’s Western glaciers as well as a period of much warmer than normal, above-freezing temperatures.
Large meltwater pulse from Jacobshavn
(Did a huge melt water pulse issue from the Jacobshavn Glacier on January 16, 2016? Dr Jason Box appears to be concerned that it has. Image source: Dr. Jason Box.)

Perhaps more ominously, this widespread clearing of ice from these Arctic bays occurs in concert with what appears to be a large ice-calving event along the ocean-facing front of the Jacobshavn Glacier. In the above graphic by Dr. Jason Box (see more here), we see a large retreat of the glacier together with what looks like a major sediment outflow. Sediment hitting water in this way would be a sign that a very large volume of water had been expelled along the basal zones of the JacobshavnIn addition, the ice itself appears to have been forcibly ejected

This apparent sediment flush, the concave bowing of sea ice away from Disko and Uummannaq and the inland recession of the calving face are all indicators that something terrible is afoot in Western Greenland.

A large flush of melt water coming from Greenland during Winter would, indeed, be that terrible thing. Something that now may become a more and more common feature of our age as Winter continues its ongoing retreat against a relentless assault by human greenhouse gas emissions.
Hat Tip to Colorado Bob

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