arctic warming
Above: Northwest Greenland 13 June 2019. Rapid melt and sea ice with low permeability and few cracks leaves the melt water on top: Courtesy Steffen M. Olsen @SteffenMalskaer Jun 14 oceanographer at the Danish Meteorological Institute (DMI). Taken at the Inglefield Fjord in northwestern Greenland, situated close to 78°N.
Although the rest of the world has observed a modest temperature increase of about 0.8 degrees Celsius since the beginning of the 20th century, average temperatures in the Arctic have warmed by more than double that over the past 50 years, and 2 to 3 times faster than the rest of the Northern Hemisphere, a phenomenon known as Arctic amplification.
This is evidenced by a global representation appearing in the 2015 National Geographic:
Temperature trends, 1960-2014
Change in degrees Fahrenheit
Although the rest of the world has observed a modest temperature increase of about 0.8 degrees Celsius since the beginning of the 20th century, average temperatures in the Arctic have warmed by more than double that over the past 50 years, and 2 to 3 times faster than the rest of the Northern Hemisphere, a phenomenon known as Arctic amplification.
This is evidenced by a global representation appearing in the 2015 National Geographic:
Temperature trends, 1960-2014
Change in degrees Fahrenheit
The map also reveals the regional varieties lurking in the global average. A few areas, mostly near the Antarctic, have actually become colder since 1960, while some parts of the Arctic have warmed as much as 15 degrees. Natural climate cycles might explain why the warming has happened unevenly and fitfully, but not the warming trend itself, which coincided over the past half century with a surge in carbon emissions from our rapidly industrialising world and in particular the burning of fossil fuels[1].
This warming trend at double the rate elsewhere in the globe has resulted in the rapid loss of summer sea ice in the Arctic, the Greenland ice sheet, permafrost (soil that usually remains frozen year round) and continental glaciers, disrupting critical habitats for the wildlife and threatening the long term survival of many species. Another consequence is the melting of the tundra, which releases the more potent greenhouse gas, methane[2] and indeed carbon dioxide, the rate of emissions being comparable to all the emissions from the US commercial sector in a year[3].
"Permafrost contains rock, frozen soil and ice, so it thaws, rather than melts, when it warms. Like hamburger pulled from your freezer, it softens but does not become liquid. As permafrost thaws, previously frozen microbes reactivate and decompose the remnants of plants and animals accumulated into the frozen soil over hundreds to thousands of years, giving off carbon dioxide and methane". Should the melting frozen permafrost give up its methane, a greenhouse gas 21 times more powerful than CO2, there is the prospect of a tipping point: irreversible climate change.[4] [4A]
In the shorter term, permafrost loss will bring about a feedback loop. “Unlike at warmer latitudes, where microorganisms in the soil constantly break down plant matter and return the carbon it contains to the atmosphere, Arctic soils have been cold enough to preserve the frozen remains of ancient plant life. But as the planet warms, soil microbes break down more and more of this carbon, sending it back into the atmosphere and worsening global warming in a troubling feedback loop”[5].
Researchers estimate that 1,460 billion metric tons of organic carbon is stored in Northern Hemisphere permafrost, almost twice as much carbon as exists in Earth's atmosphere. The top three metres of soil in the northern permafrost region alone hold 50% as much carbon as the top three metres of soil everywhere else on the planet, even though the region represents only 15% of the global soil area.
The Permafrost Carbon Network estimates that between 5 and 15% of the permafrost carbon pool is likely to be released this century, most of it as carbon dioxide. At 10%, 140 billion to 160 billion metric tons of carbon would enter the atmosphere, accelerating global warming. The future release of gases will not be a rapid burst that could alter climate abruptly, as was once feared feared, but it will indeed be widespread and sustained over many decades, seriously compounding the daunting challenge that we as a society already face to slow global warming.
There are also other feedback processes in place. As ice in permafrost melts and drains away, the ground subsides, which then causes permafrost to thaw more abruptly. Could widespread subsidence boost emissions forecasts even more?
Another aspect is that in some years, 2014 in particular, the Greenland ice sheets have found themselves coated by a mixture of coal dust from coal-fired power stations and bushfires, turning black in the process, thereby diminishing the ice’s albedo (its propensity to reflect light)[7]:
Burning coal indirectly fuels sea level rise by warming the atmosphere and oceans. But coal dust and other airborne particles also directly fuel sea level rise by settling on ice and melting it quicker.
[1] Source: http://ngm.nationalgeographic.com/2015/11/climate-change/introduction-text
[2] For information on how methane is impacting the Arctic, see the EPA report Methane and Black Carbon Impacts on the Arctic.
[3] http://www.smh.com.au/environment/alaskas-tundra-is-filling-the-atmosphere-with-carbon-dioxide-20170509-gw0pkq.html; http://news.nationalpost.com/news/world/alaskas-tundra-is-filling-the-atmosphere-with-carbon-dioxide-and-thats-worsening-climate-change
[4] David Attenborough's Climate Change: The Facts, BBC, 2019, at 39.30. From 11 August 2019, available for a short period for viewing on ABC iView.
[4A] Ted Schuur, "The Permafrost Prediction", Scientific American's special edition on climate change, Summer 2020, 20-25.
[5] Attenborough, op cit. See also Jennifer A. Francis, (research professor in the department of marine sciences at Rutgers University, 1994-2018, and a specialist in Arctic climate change and its links to weather worldwide), “Meltdown – The Arctic climate is shattering record after record, altering weather worldwide”, Scientific American, April 2018, 40-45. She also mentions meltwater from the shrinking Greenland ice cap contributing to rising sea levels as a contributing cause.
[6] Schuur, op cit. Also, Jennifer Francis (by this time a senior scientist at the Woods Hole Research Centre in Falmouth, Mass), Ibid, reproduced in Scientific American Special Climate Change Edition, Summer 2020, 12-17.
[7] http://www.huffingtonpost.com.au/2017/06/06/the-dark-dirty-coal-secret-you-never-hear-anything-about_a_22127672/ (Huffington Post report dated 7 June 2017)
In closing this segment, let’s have a look at 2016 as a representative example of the Arctic melt phenomenon in all its aspects *:
During this year:
- The average surface air temperature for the year ending September 2016 was by far the highest since 1900, and new monthly record highs were recorded for January, February, October and November 2016.
- After only modest changes from 2013-2015, minimum sea ice extent at the end of summer 2016 tied with 2007 for the second lowest in the satellite record, which started in 1979.
- Spring snow cover extent in the North American Arctic was the lowest in the satellite record, which started in 1967.
- In 37 years of Greenland ice sheet observations, only one year had earlier onset of spring melting than 2016.
- The Arctic Ocean is especially prone to ocean acidification, due to water temperatures that are colder than those further south. The short Arctic food chain leaves Arctic marine ecosystems vulnerable to ocean acidification events.
- Thawing permafrost releases carbon into the atmosphere, whereas greening tundra absorbs atmospheric carbon. Overall, the tundra is presently releasing net carbon into the atmosphere.
- Small Arctic mammals, such as shrews, and their parasites, serve as indicators for present and historical environmental variability. Newly acquired parasites indicate northward shifts of sub-Arctic species and increases in Arctic biodiversity.
The result bespeaks itself in an inevitable and ongoing diminution in Arctic sea ice.
* This summary is drawn from the report of the National Oceanic and Atmospheric Administration (NOAA - an American scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere). For the report, see http://www.arctic.noaa.gov/Report-Card/Report-Card-2016
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