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

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)

Permafrost potential is declining…

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)

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. 

Greenland ice mass loss and melt extent

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)

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)

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 38^th 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