Sea ice is a critical factor in the global climate crisis. Although melting sea ice does not contribute directly to sea level rise, it causes the oceans to warm due to the loss of reflectivity; the dark ocean absorbs solar radiation rather than reflecting it. That has major flow-on effects, such as increased warming of the Greenland ice sheet.
Unlike the melting of sea ice, melting ice sheets (on land) do contribute to sea level rise. Any eventual melting of the Greenland ice sheet would raise sea levels nearly 7 metres, while the figure for Antarctica would be around ten times higher.
Leading climate scientist, Dr James Hansen, has said that he finds it difficult to imagine the Greenland ice sheet surviving if Arctic sea ice were to be lost entirely in the warm season.
The area (extent) of sea ice increases and falls with the seasons. In the Arctic, the annual minimum is reached during September, while in the Antarctic, that month or October represents the annual maximum.
An alarming development in October 2016 has been the slump in the extent of sea ice relative to the same month in previous years. The fall is demonstrated by these charts for the Arctic (northern hemisphere) and Antarctic (southern hemisphere) from the National Snow and Ice Data Center in the US. The Arctic sea ice reached its lowest October level in the satellite record (from 1979), while Antarctica was at its second lowest.
Figure 1: Northern and southern hemisphere sea ice extent anomalies for month of October 1979 – 2016
If we consider the Arctic in isolation, here’s how the trend for October compares to September, with a significant fall this year for the former. While the average sea ice extent for September was similar to that of the same month last year, October was 19 per cent lower than October 2015.
Figure 2: Arctic Sea Ice Extent 1979-2016 for months of Sep and Oct (million sq km)
Even those dramatic results only tell part of the story. While the area of Arctic sea ice is reducing, so is the thickness and therefore the volume. This chart compares the change in area (in blue) and volume (in red), with the latter reducing 73 per cent in 37 years.
Figure 3: Arctic Sea Ice Extent and Volume September 1979-2016
Thicker ice tends to be older and more robust than thinner ice, and its extent has reduced significantly in the Arctic.
At the time of this year’s minimum Arctic sea ice extent, only 106,000 square kilometres of ice 4 years or older remained, representing 3.1 per cent of the total. That compares to the mid-1980s, when ice of that age covered over 2 million square kilometres, representing 33 per cent of the summer minimum extent, with the change representing a reduction of 95%.
The comparison is depicted in the following slideshow.
These changes are dramatic but possibly not surprising given the rapid increase in global temperatures, with the increase in the Arctic being multiples of the average.
On 14th November 2016, the World Meteorological Organization reported that 2016 is very likely to be the hottest year on record, with preliminary data indicating that global temperatures are approximately 1.2°C above pre-industrial levels. Here’s WMO’s temperature chart, showing a significant spike in 2016.
Figure 4: Global temperatures – change from pre-industrial
The WMO stated that temperatures in parts of Arctic Russia were 6°C to 7°C above average, while many other Arctic and sub-Arctic regions in Russia, Alaska and northwest Canada were at least 3°C above average.
The following slideshow demonstrates the increase in global temperatures from 1884 to 2015, with a very rapid increase from 1980.
Abrupt climate change?
Could we be seeing abrupt climate change in action? The following comments from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in 2011 may reflect our current reality:
“Climate change does not proceed smoothly for a given change in radiative forcing from changing greenhouse gas levels. There is a risk of abrupt changes as the climate shifts from one state to another as a result of feedbacks in the climate system. . . . Their hazard lies in the fact that, once they have occurred, it may be hard for the planet to return to its previous steady state. For example, once Greenland’s ice cap is committed to melting it is unlikely to reform for thousands of years, leading eventually to sea level rises of several metres.”
Emergency action is required
Our current predicament requires emergency action far beyond current voluntary commitments stemming from the 2015 Paris climate conference. Despite the impression to the contrary generally portrayed by governments and media, those commitments are expected to lead to average global warming of 3.5°C in the absence of progress beyond the pledge period (up to 2030).
To put that figure in perspective, Professor Hans Joachim
Author
Paul Mahony (also on Twitter, Facebook, Scribd, Slideshare, New Matilda, Rabble and Viva la Vegan)
Additional comment regarding Antarctic sea ice
There has been an upward trend in Antarctic sea ice extent through a combination of winds and ocean circulation. The increase has been more than offset by contraction in the Arctic, which has been accelerating. Since satellite records began in 1979, the extent of sea ice has reduced an average of 35,000 square kilometres per annum globally. That comprised 21,500 sq. km from 1979 to 1996 and 50,000 sq. km from 1996 to 2015, with the latter being equivalent to 74 per cent of the Australian state of Tasmania and 80 per cent of the US state of West Virginia. (There have also been extremely concerning developments in relation to the West Antarctic and East Antarctic ice sheets, including reports that the glaciers in the Amundsen Sea sector of West Antarctica had “passed the point of no return”.)
Sources
Hansen, J., “Storms of my grandchildren”, p. 164
U.S. Geological Survey, “Sea Level and Climate”, last updated 27th October 2016, http://water.usgs.gov/edu/sealevel.html
National Snow & Ice Data Center, Sea Ice Index, Monthly Sea Ice Extent Anomaly, Arctic, http://nsidc.org/data/seaice_index/ and Antarctic, http://nsidc.org/data/seaice_index/
National Snow & Ice Data Center, Arctic Sea Ice News and Analysis, “Sluggish Ice Growth in the Arctic”, 2 Nov 2016, http://nsidc.org/arcticseaicenews/2016/11/sluggish-ice-growth-in-the-arctic/
World Meteorological Organization, “Provisional WMO Statement on the Status of the Global Climate in 2016”, 14th November 2016, http://public.wmo.int/en/media/press-release/provisional-wmo-statement-status-of-global-climate-2016
National Oceanic and Atmospheric Administration, Sea Ice and Snow Cover Extent, Sea ice for northern hemisphere Sep and Oct, https://www.ncdc.noaa.gov/snow-and-ice/extent/, https://www.ncdc.noaa.gov/snow-and-ice/extent/sea-ice/N/9; https://www.ncdc.noaa.gov/snow-and-ice/extent/sea-ice/N/10
National Snow & Ice Data Center, “State of the Cryosphere, SOTC: Sea Ice”, https://nsidc.org/cryosphere/sotc/sea_ice.html
NASA Scientific Visualization Studio, “Rapid ice growth follows the seasonal minimum, rapid drop in Antarctic extent”, 5th Oct 2016, http://nsidc.org/arcticseaicenews/2016/10/rapid-ice-growth-follows-the-seasonal-minimum-rapid-drop-in-antarctic-extent/
NASA Scientific Visualization Studio, “Weekly Animation of Arctic Sea Ice Age with Graph of Ice Age by Percent of Total: 1984 – 2016”, https://svs.gsfc.nasa.gov/4509
Whetton, P, “Future Australian Climate Scenarios”, Chapter 3, p. 43 “Climate Change”, CSIRO Publishing, 2011, Cleugh, H; Stafford Smith, M; Battaglia, M; Graham, P (Editors), http://www.publish.csiro.au/Books/download.cfm?ID=6558 (Accessed 4 February 2012)
Tschudi, M.A., J.C. Stroeve, and J.S. Stewart. 2016. Relating the age of Arctic sea ice to its thickness, as measured during NASA’s ICESat and IceBridge campaigns. Remote Sensing, 8, 457, doi:10.3390/rs8060457, cited in NASA Scientific Visualization Studio, “Rapid ice growth follows the seasonal minimum, rapid drop in Antarctic extent”, op. cit.
NASA Earth Observatory, Despite Antarctic Gains, Global Sea Ice Is Shrinking, 11th Feb 2015, http://earthobservatory.nasa.gov/IOTD/view.php?id=8524685246
Climate Interactive, https://www.climateinteractive.org/tools/scoreboard/, cited in Spratt, D. “Climate Reality Check: After Paris, counting the cost”, 2016
Manning, P. “Too hot to handle: can we afford a 4-degree rise?”, Sydney Morning Herald, 9th July 2011, http://www.smh.com.au/environment/too-hot-to-handle-can-we-afford-a-4degree-rise-20110708-1h7hh.html
Images
Main image: U.S. Geological Survey, “Arctic Ice (The clouds begin to thin over the Arctic Ocean Aug. 19, 2009)”, Public Domain
Global temperature chart: World Meteorological Organization, op. cit., Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Slideshow images:
NASA Global Climate Change, Global Temperature, http://climate.nasa.gov/vital-signs/global-temperature
NASA Scientific Visualization Studio, “Weekly Animation of Arctic Sea Ice Age with Graph of Ice Age by Percent of Total: 1984 – 2016”, https://svs.gsfc.nasa.gov/4509
Note
The information contained in this article was included in a presentation given by the author on 15th November 2016.
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