Melting of the Permafrost and Rising Sea Levels

MELTING OF THE PERMAFROST & RISING SEALEVELS

          As may be evident by now, the lines between effects of global warming to the ocean are blurred. There are no distinct cut-offs. Warmer oceans and rising sea levels are not distinct, but compound each other. The same goes for the melting of the permafrost and rising sea levels. Relationships between permafrost melt and warmer oceans can be found also. The point is that the issues surrounding our present day oceans are nut cut and dry, they are fluid (no pun intended). This page, therefore, may have some redundancies when it comes to sea-level rise, but I believe it is important to tackle this phenomenon from different angles. My goal in this section is to review the current literature surrounding specifically melting of the permafrost: glaciers, mountain snowpack, and other forms of ice that have been frozen for thousands of years. I will also discuss the consequences of the melting of ice pack, with regards to biological systems and humans.

Warmer planet = less permafrost. 

Research

          The current literature on global warming indicates that the Arctic regions of our planet warmed at nearly twice the rate of equatorial latitudes (Ardt et al. 2011).  The Cryosphere, areas containing large masses of snow and ice not necessarily in the Arctic regions, is also expected to continue to lose mass in the coming decades (Scambos, 2011). Records of ice mass in Greenland show that it has lost more mass in the past decade than in any other recorded period in history, with the melt rate recorded at its highest since 1958.  Due to abnormally high summer temperatures, coupled with a melt season that is historically longer than typical, the Canadian Arctic experienced an increase in the rate of ice loss from glaciers and ice caps. Glaciers have always fluctuated throughout history in size, but the current rate of loss has not been seen before. Our planet has seen loss of mass in alpine glaciers for 20 years straight, and permafrost (water typically locked up for long periods of time) temperatures have risen by 2^oC in the past three decades (Arndt et al. 2011). So what is causing all of this?

          We have heard the data before, but here it is again: atmospheric CO₂ concentrations have increased dramatically since the industrial age, and have remained between 2 and 4 times as high as levels previously seen. Huybrechts and colleagues estimate that at our current CO₂ levels the Greenland ice sheet will be completely lost within the next 3,000 years- a blink of an eye in geological time (Huybrechts et al. 2011). HIS/HER team investigated scenarios based on current CO₂ levels, and found that this and other ice loss in the Antarctic could contribute to more than 4 meters of sea level rise in that time period! Losses in permafrost mass shouldn’t be instantaneous in all cases, however. Some models indicate that the Antarctic ice sheets will actually grow in the next 1200 years or so. This increase in size is due to increased predictions for rain as the planet continues to warm. This rain will accumulate in the Arctic region, which will remain cold enough for ice formation.  This accumulation trend is expected to revert to loss trends after the initial 1200 years. This is still under debate though, as some studies have shown a net loss of 100-200 gigatons of ice per year from each ice sheet each year into the ocean. It takes 360 gigatons of ice to raise the sea by 1 millimeter, according to one estimate (Scambos, 2011).  It is unanimously accepted that lower latitudinal ice sheets can expect to see losses much sooner, however.

          Summer ice has been at record and near-record low levels in recent years.  The Himalayan and Tibetan Plateau Glaciers have been experiencing a widespread loss of their glaciers and snow cover (Prasad et al. 2009). This is soley due to the fact that the globe has warmed the cryosphere to the point or near the point of freezing, postulates Scambos and colleagues. Scambos further states that the processes leading to the loss of ice are easily set in motion, but are not easily reversed. Melting permafrost may therefore create a sort of cascade effect that may be irreversible. Recent changes in wind pattern due to global warming have also been proposed as exacerbating the ice melt problem by pushing ice into warmer water (Scambos, 2011). This idea will be touched upon more extensively in the next tab (Changes to Major Ocean Currents).

One example of a retreating glacier in Canada

Consequences

         

          So why should we care about permafrost melt? The reasons are many. Biological systems in the Arctic oceans would be majorly disrupted by an environment with no or little ice. This includes both terrestrial and marine ecosystems. These marine ecosystems will most likely see a change in primary production (phytoplankton mass) and general water flow patterns, which could affect entire food webs, all the way up to our charismatic Polar Bears (Huybrechts et al. 2011). One study even shows that chemical cycling, especially the carbon cycle related to carbohydrates in primary producers and consumers, could be dramatically altered if ice dissipates in the Arctic. This would affect the ‘biological pump’ that keeps many ecosystems running in the Arctic regions, thereby negatively impacting the entire biome (Sala et al. 2010).  Humans may further stress the Arctic environment as ice melts, because more ocean would open to previously unavailable fisheries. It is clear that ice melt will have far reaching implications in the biological realm.

Decrease in ice pack will have far reaching consequences for biota in Arctic regions. 

          Beyond biological diversity issues, many concerning consequences will be directly experienced by humans.  Vast areas in Asia will have dramatically altered water tables if ice melt continues. Major rivers, such as the Indus, Ganga and Brahmaputra, are fed by glacial meltoff. A complete melting of ice sheets will therefore negatively impact agriculture and water resources in an already stressed region of the world (Prasad et al. 2009).  Areas that are considered lowlands will also see increases in flooding and debris flow due to melting glaciers, a consequence of rising sea levels and deteriorating alpine cold meadows. Land in these areas will also experience erosion at greater rates than previously seen, due to freeze and thaw patterns atypical to the region. These increased flooding and debris patterns, along with heightened erosion, will affect some of the most densely populated areas of the world, specifically China and India (Zhang et al. 2011).  

Some tropical areas of the world may be completely covered if the oceans continue to rise.