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16227
From: ryan, [DNS_Address]
Subject: Greenland is melting
URL: https://thehill.com/opinion/energy-environment/449493-greenland-is-melting
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Summer has arrived in the Arctic, and an early start to melting of the Greenland ice sheet is threatening the Arctic’s largest ice mass. In the past week, an area larger than the state of Texas was melting, covering more than 275,000 square miles. Normally, temperatures at Summit Station — so named because it lies atop the ice sheet at nearly 10,600 feet above sea level — have an average high temperature of only 12 degrees Fahrenheit in June. But on June 12, the temperature neared 32 degrees. Two images from this event have captured the attention of international media. The first was a graph produced at the National Snow and Ice Data Center with a near vertical line showing the dramatic increase in the area melting. Current weather conditions (-NAO pattern) have resulted in the first major Greenland Ice Sheet surface melt event of the summer More information: https://t.co/5Z7Gu1BxUP MARv3.9 model: https://t.co/xeu1qQ3ksc pic.twitter.com/sXNXyMCxdR — Zack Labe (@ZLabe) June 13, 2019 The second was a photograph showing a dogsled team mushing through ankle deep meltwater on top of sea ice. The juxtaposition of the image and data provide a compelling message about the changing environment in and around the Greenland ice sheet. This photo of sled dogs walking through water shows the reality of Greenland's melting ice sheet https://t.co/36q2KSh3jf pic.twitter.com/JFFEoVyOKl — CNN (@CNN) June 18, 2019 The Greenland ice sheet is roughly the size of Alaska and contains enough ice to raise global sea level by more than 20 feet. Greenland gains ice each year through snow accumulation. It loses ice through icebergs breaking off the margin and meltwater that drains through the ice and into the ocean. ADVERTISEMENT Each summer, a large portion of the surface of the ice sheet melts, with the most widespread melt typically occurring in mid-July. During the past two decades, the ice losses have been greater than the snowfall. A NASA satellite showed that the ice sheet shed an average of 280 gigatons (Gt, billions of tons) per year between 2002 and 2016. For reference, 1 Gt is roughly the amount of water needed to fill 400,000 Olympic size swimming pools. The greatest loss of ice in the modern era occurred in 2012, when nearly the entire surface of the ice sheet experienced melt in mid-July that year, including Summit, which last had melt in the 1880s. The ice sheet lost a massive 627 Gt that summer, and floods were reported along rivers from raging meltwater. The past three summers have seen more modest melt, but a warmer than normal spring and the extensive melt so far this year is likely to lead to massive losses this summer. ADVERTISEMENT The satellite data are collected from a series of NOAA and Department of Defense satellites that record naturally emitted microwave radiation. Wet snow and ice appear bright in these images, compared to dark areas of dry snow. Unprecedented melt area extent on the Greenland Ice Sheet. Technically the melt season (defined as 3 consecutive days of >1Gt loss) has not started yet! Complicated season with lots of surface melting, snowfall and refreezing. See @greenlandsmb for more. pic.twitter.com/QEusbTQ0S9 — Ice Alive (@icealivetweets) June 13, 2019 This contrast of dry and wet snow allows us to map the melt area each day during the past four decades. The near vertical line on June 12 was due to the rapid expansion of melt following the incursion of warm, humid air from the Atlantic Ocean over the ice sheet. The melt area increased to more than 275,000 square miles on June 12 and remained well above the long-term average for the remainder of the week, and the ice sheet lost more than 2Gt of ice per day based on model estimates by Danish Meteorological Institute (DMI). Also that day, the dramatic photo of the dogsled was taken by Steffen Olsen of DMI in Inglefield Bredning, near the village of Qaanaaq. Four scientists and local hunters were trying to retrieve scientific instruments but were inhibited by the melting snow over the sea ice. DMI reported to The Guardian that they had retrieved the weather station monitoring equipment after the watery crossing. John Cappelen of DMI recorded a maximum temperature of 63 degrees Fahrenheit (17.3 degrees Celsius) at nearby Qaanaaq on June 12 and 59 degrees Fahrenheit (15 degrees Celsius) on June 13, which is exceptionally warm for 700 miles into the Arctic Circle. The early onset to melt has important implications for the remainder of the summer. At the beginning of spring, fresh snow and compacted snow from previous years (called firn) is much colder than the freezing point. The snow and firn must be warmed to freezing before melt can start. Once melt is underway, the snow remains near the freezing point even after refreezing. Not all meltwater goes into the ocean; the firn has pores, like a sponge, that allows some of the meltwater to refreeze and acts as a buffer to sea level rise, but increasing surface melt is filling the pores, which will lead to more meltwater runoff into the ocean. Meanwhile, snowmelt along the margin of the ice sheet also exposes bare glacial ice and allows surface meltwater ponds to fill. The refrozen snow and firn, bare ice, and meltwater ponds are much darker and absorb more sunlight than fresh snow, promoting even more melt. For perspective, extensive melt in early June does not appear in the satellite record prior to 2000. The three years since 2000 that had extensive melt in early June ended with massive ice losses. Greenland melt is an increasingly significant contributor to global sea level rise, affects the ocean food web, and may alter ocean circulation and global weather patterns. The early start to summer on the Greenland ice sheet is not occurring in isolation. Sea ice extent in the Arctic is near record low levels for June, numerous wildfires are being tracked in Siberia above the Arctic Circle, and new evidence suggests Arctic permafrost is melting faster than expected. Earth's complexity and changes are scientifically interesting, but also have real implications for our Arctic policy, national security, and our coastal infrastructure. Thomas Mote is a distinguished research professor of Geography and Atmospheric Science at the University of Georgia. He has published research for the past 25 years on Arctic climate change and the use of regional climate models and remote sensing to monitor the Greenland ice sheet. He provides the processed satellite data for the Greenland Today website at the National Snow and Ice Data Center. |
16228
From: pamela, [DNS_Address]
Subject: Re: Greenland is melting/take it from the horses mouth
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the NSIDC are the ones measuring the melt, also see Polar Portal, a reference in video - link I made post other day to: http://earthboppin.net/talkshop/survive/messages/3905.html Greenland Ice Sheet Today is produced at the National Snow and Ice Data Center by Ted Scambos, Julienne Stroeve, and Lora Koenig with support from NASA. NSIDC thanks Jason Box, Xavier Fettweis, Chris Shuman, and Thomas Mote for data and collaboration. April and May: Above average, but nothing to write Nome about June 12, 2019 Surface melting on the Northern Hemisphere’s largest mass of ice began during the second week of April, with several significant melting episodes at the end of the month and into early May. Warm conditions over the ice sheet and winds from the east were prevalent for the two-month period. While significant, and above average for the 1981 to 2010 reference period, the melting extent has been comparable to previous years spanning 2010 to 2018. see rest of article at link plus the graphics and charts. after seeing/reading article, see this link and yet Greenland ice is still growing. http://earthboppin.net/talkshop/survive/messages/3905.html |
16230
From: ryan, [DNS_Address]
Subject: Re: Greenland is melting/take it from the horses mouth
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the two articles are not mutally exclusive...this is the key line from my post... "...a warmer than normal spring and the extensive melt so far this year is likely to lead to massive losses this summer." |
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16229
From: ryan, [DNS_Address]
Subject: Re: Greenland is melting/take it from the horses mouth
| i don't consider David DuByne a reliable source... |
Responses:
[16231]
16231
From: pamela, [DNS_Address]
Subject: Re: Greenland is melting/take it from the horses mouth
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Hi Ryan, DuByne is not the source- just reporting what the sources are saying. He shows the same articles from NASA, NSIDC, and more sources in the video links he has in the bottom and says :I will let you decide. DuByne quotes a CNN article showing Dr Mote says this:https://m.cnn.com/en/article/h_5dbcef45e1f2fbf5038b0e3c31a1566b The sudden spike in melting "is unusual, but not unprecedented," according to Thomas Mote, a research scientist at the University of Georgia who studies Greenland's climate.((the writer of the Hill article)) "It is comparable to some spikes we saw in June of 2012," Mote told CNN, referring to the record-setting melt year of 2012 that saw almost the entire ice sheet experience melting for the first time in recorded history. This much melting this early in the summer could be a bad sign, indicating 2019 could once again set records for the amount of Greenland ice loss. Mote explained how snow and ice melt off the Greenland ice sheet, especially early in the season, makes it easier to for additional melt to occur later in the summer. White snow and ice, which is bright and reflects the sun's rays back into space, reduces the amount of heat that is absorbed and helps to keep the ice sheet cold, a process known as "albedo." "These melt events result in a changed surface albedo," according to Mote, which will allow more of the mid-summer sun's heat to be absorbed into the ice and melt it. Predictions for a record melt season Mote says "all signs seem to be pointing to a large melt season," and he is far from the only scientist to think so. Jason Box, an ice climatologist at the Geological Survey of Denmark and Greenland, predicted in late May that "2019 will be a big melt year for Greenland." Box pointed out that this year had unusually early-season melt days in April, and the melt season was "happening about three weeks earlier than average, and earlier than the record-setting melt year of 2012." In addition to the early-season melt, the snow cover is already lower than average in Western Greenland, and combining these factors means "2019 is likely going to be a very big melt year, and even the potential to exceed the record melt year of 2012." What is causing the sudden melt? A persistent weather pattern has been setting the stage for the current spike in melting, according to Mote. "We've had a blocking ridge that has been anchored over East Greenland throughout much of the spring, which led to some melting activity in April -- and that pattern has persisted." That high pressure ridge pulls up warm, humid air from the Central Atlantic into portions of Greenland,.which leads to warmer temperatures over the ice. The high pressure also prevents precipitation from forming and leads to clear, sunny skies. Over the past week or two, that high pressure ridge got even stronger as another high pressure front moved in from the eastern United States -- the one that caused the prolonged hot and dry period in the Southeast earlier this month. Melt periods such as the current one are not unprecedented; Mote noted previous periods in 2012, 2010 and 2007, all major melt years. But he pointed out that until recently, they were unheard of. "We've seen a sequence of these large melt seasons, starting in 2007, that would have been unprecedented earlier in the record," he said. "We didn't see anything like this prior to the late 1990s. If these extreme melt seasons are becoming the new normal, it could have significant ramifications around the globe, especially for sea level rise. "Greenland has been an increasing contributor to global sea level rise over the past two decades," Mote said, "and surface melting and runoff is a large portion of that." I guess we will find out which way it goes; if it's the conclusion. THe Hill writer, Dr Mote and DuByne, both cite the same article. http://nsidc.org/greenland-today/category/uncategorized/ THe Hill: "...a warmer than normal spring and the extensive melt so far this year is likely to lead to massive losses this summer." This is the whole quote: "The past three summers have seen more modest melt, but a warmer than normal spring and the extensive melt so far this year is likely to lead to massive losses this summer." DuByne goes on to show the other data: ALL cited from within the same article as the Hill/Dr Mote, writer cites and DuByne shows Greenland Ice Spike graphics https://pbs.twimg.com/media/D9BUmLPXYAA37cw.jpg Greenland melt extent https://pbs.twimg.com/media/D9ALKO2UIAEwSLL.png Greenland data http://polarportal.dk/en/greenland/surface-conditions/ High pressure system https://pbs.twimg.com/media/D9HB5D9W4AQ3nhc.jpg When I referred to the horses mouth, I meant those who do the science. So if its seen as unusual but not unprecedented by Dr Mote, I guess we shall see. |
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