Climate Change: Cryosphere


Greenland Ocean Sunset  Photo by William Bossen on Unsplash

Arctic Regions: Permafrost, Sea Ice

Permafrost

Over the 1900 to present time span roughly 4.5 Million sq km of potential permafrost area has been lost. Berkeley Earth Permafrost


Map of estimated 0 to 3 m deep carbon inventory stored in the circum-Arctic permafrost region (Hugelius et al., 2014Kanevskiy et al., 2011Romanovskii, 1993). The eastern boundary of Canadian Yedoma areas is uncertain, indicated as a dotted line at the Alaskan/Yukon state border. The conceptual permafrost carbon climate feedback cycle is illustrated in the middle. The Yedoma domain marks the potential maximum occurrence of widespread Yedoma deposits but also includes other deposits that formed after degradation of Yedoma, such as thermokarst deposits. In West Siberia and the Russian Far East Yedoma occurs sporadically, e.g. in river valleys. (Deep Yedoma permafrost)

(Permafrost Carbon Network); Global carbon storage in soils and atmospheric carbon

Significance:  Approximately 1330-1580 Pg of soil carbon are estimated  to be stored in soils and permafrost of high latitude ecosystems, which is almost twice as much carbon as is currently contained in the atmosphere. In a warmer world permafrost thawing and decomposition of previously frozen organic carbon is one of the more likely positive feedbacks from terrestrial ecosystems to the atmosphere. Although ground temperature increases in permafrost regions are well documented there is a knowledge gap in the response of    permafrost carbon to climate change. (Permafrost Carbon Network)

Total estimated carbon storage is ~1300 Pg with an uncertainty range of between 1100 and 1500 Pg. Around 800 Pg carbon is perennially frozen, equivalent to all carbon dioxide currently in the Earth’s atmosphere. (Permafrost Carbon)


Global carbon storage in soils and atmospheric carbon

Permafrost potential is declining…


This figure shows the decline in permafrost potential over the 1850 to 2013 time period. The permafrost potential is defined by the decadal air temperature. If the annual average temperature over a 10 year period is 0C or below, then that area was regarded as permafrost. Over the 1900 to present time span roughly 4.5 Million sq km of potential permafrost area has been lost. Berkeley Earth Permafrost

Arctic Sea Ice

Average September (summer minimum) Extent Declining at -12.8%/decade (relative to 1981-2000 average

Ice Sheets: Antarctica, Greenland, The Third Pole

An ice sheet is a mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles). The two ice sheets on Earth today cover most of Greenland and Antarctica. During the last ice age, ice sheets also covered much of North America and Scandinavia.

Together, the Antarctic and Greenland ice sheets contain more than 99 percent of the freshwater ice on Earth. The Antarctic Ice Sheet extends almost 14 million square kilometers (5.4 million square miles), roughly the area of the contiguous United States and Mexico combined. The Antarctic Ice Sheet contains 30 million cubic kilometers (7.2 million cubic miles) of ice. TheGreenland Ice Sheet extends about 1.7 million square kilometers (656,000 square miles), covering most of the island of Greenland, three times the size of Texas.

Antarctica

-127.0 Gt per year +/- 39 (Mass variation since 2002)


Zodiac Cruising in Antarctica  Photo by James Eades on Unsplash
Ice mass measurements by NASA’s GRACE satellites

Source:  NASA Global Climate Change Ice Sheets

Elephant Island, Antarctica  Photo by Paul Carroll on Unsplash

Greenland

  • Greenland ice sheet is a major contributor to sea level rise, adding on average 0.47mm +/- 0.23 mm/year to global mean sea level between 1991 and 2015
  • The cryosphere as a whole has contributed around 45% of observed global sea level rise since 1993. 
  • Observations show surface lowering across virtually all regions of the ice sheet and at some locations up to -2.65m/year between 1995 and 2017

Overall Greenland has lost 255+/- 15 Gt/year of ice over the period 2003-2016, compared to a rate loss of 83 +/- 63 Gt/year in the 1993-2003 period. 

Narsarsuaq, Greenland
Photo by Mahlersilvan on Unsplash

Greenland ice mass loss and melt extent


(a) Mass change time series for the entire Greenland ice sheet generated by DTU (red) and TUDR (blue). (b) Ice mass trends for 2007–2011 provided by DTU (left) and TUDR (right).
(TUDR  Technische Universitat Dresden; DTU Technical University of Denmark)
Source:  Greenland Ice Sheet Mass Balance

Source:  NSIDC Greenland Today

Melting ice sheets contribute to sea level rise

Source:  Denmark Polar Portal

Mass Change and Contribution to sea level rise 2003-2016

The map shows the latest changes in mass derived from data from the GRACE satellites.  The graph show the gain in the mass of ice when there is precipitation, and how much of this mass is lost when snow and ice melt and when icebergs break off from the ice sheet’s major outlet glaciers. The difference in these mass changes over a glaciological year (September-August) is called the total mass balance of the Greenland Ice Sheet.

The graph illustrates the month-by-month development in changes of mass measured in gigatonnes, Gt (1 Gt is 1 billion tonnes or 1 km3 of water). The left axis on the graph shows how this ice mass loss corresponds to sea level rise contribution. 100 Gt corresponds to 0.28 mm global sea level rise).  All changes are given relative to June 2006.

Based on this data, it can be seen that during the period 2003-2011 the Greenland Ice Sheet has lost 234 km3 of water per year, corresponding to an annual contribution to the mean increase in sea level of 0.65 mm 

This data shows that most of the loss of ice occurs along the edge of the ice sheet, where independent observations also indicate that the ice is thinning, that the glacier fronts are retreating in fjords and on land, and that there is a greater degree of melting from the surface of the ice.  (See map)

High on the central region of the ice sheet, however, the GRACE satellites show that there is a small increase in the mass of the ice. Other measurements suggest that this is due to a small increase in precipitation/snowfall.  (See map)

The Third Pole (Hindu-Kush and the Tibetan Plateau) (Source:  Science magazine Acceleration of ice loss)


Drekong Monastery, Tibet Autonomous Region, China  Photo by Evgeny Nelmin on Unsplash

Significance: 

  • Contains the largest volume of freshwater outside of the polar regions.
  • One-seventh of the world’s population depends on rivers flowing from these mountains for water to drink and to irrigate crops
  • Average ice loss during 2000-2016 (-0.43 +/- 0.14 meters water equivalent/year) is double compared to 1975-2000 (-0.22 +/- 0.13 meters water equivalent)
  • Acceleration of mass loss is consistent with warming temperatures recorded by meterological stations in the region

Glacier Mass Balance

Source: (NOAA CLIMATE CHANGE GLACIER)


Glacier Bay, Alaska  Photo by Michael Denning on Unsplash

Significance:  Today, many glaciologists are more concerned with predicting when various glaciers will disappear. In many parts of the world—including the western United States, South America, China, and India—glaciers are frozen reservoirs that provide a reliable water supply each summer to hundreds of millions of people and the natural ecosystems on which they depend. NOAA CLIMATE CHANGE GLACIER

  • 2018:  -0.72 meters water equivalent*   World Glacier Monitoring Service
  • Among the most dramatic evidence that Earth’s climate is warming is the dwindling and disappearance of mountain glaciers around the world. Based on preliminary data, 2017 is likely to be the 38th year in a row of mass loss of mountain glaciers worldwide. According to the State of the Climate in 2017

The cumulative mass balance loss from 1980 to 2016 is -19.9 meters, the equivalent of cutting a 22-meter-thick (72-foot-thick) slice off the top of the average glacier.

The graph shows cumulative mass loss in “*meters of water equivalent,” which is the depth of the meltwater spread out over the glacier’s surface area.

Melting of mountain glaciers has accelerated since 2000

Glacier mass balance (gray bars) from 1980–2017 for 37 worldwide glaciers with at least a 30-year monitoring history. Observations for 2017 are preliminary. Cumulative mass losses (orange line) have accelerated since 2000. As of 2016, the total loss was -19.9 meters, the equivalent of cutting a 22-meter- (72-foot-) thick slice off the top of the average glacier. NOAA Climate.gov graph adapted from State of the Climate in 2017.

Mer de Glace, Chamonix, France
 
Photo by Martin Adams on Unsplash

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