Global Consequences of Arctic Environmental Change

from Lloyd’s Report 2012: Arctic Opening – Opportunity and Risk in the High North

As well as being affected by climate change, the Arctic itself also significantly affects global environmental change. The Arctic is crucial to global and regional weather patterns: anomalously large winter snowfall across Europe, North America and East Asia has been attributed to changes in Arctic sea ice¹ . The feedback loops that contribute to ‘Arctic amplification’ tend to accelerate global warming, while methane release from the melting of both onshore and seabed permafrost may increase atmospheric greenhouse gas concentrations. Many of the uncertainties in global climate models – crucial for determining appropriate policy responses – lie in Arctic processes. The importance of Arctic science to global climate science is shown in the greater priority given to polar science in recent years by both national and international research bodies.

The main global consequence of Arctic environmental change is through a diminishing Greenland ice sheet. This is a long-term process. But, even over the course of the 21st century, it could have ramifications far beyond the Arctic.

The Greenland ice sheet contains approximately 2.85 million cubic kilometres of freshwater. Unlike annual sea ice melt, only a tiny proportion of this overall volume melts each year, and much of that is compensated for by fresh snowfall onto Greenland. However, also unlike with sea ice, any net reduction in the mass of ice on Greenland contributes directly to global sea levels (xiii). Satellite measurements indicate that the mass of ice on Greenland is indeed declining² .

For a range of reasons – including meltwater lubrication of the underside of glaciers, feedback mechanisms and the general trend of global warming – the rate of decline is accelerating³ . Total ice sheet loss in 2011 was 70% greater than the average of 2003–2009⁴ . The number of melt days in 2011 was far above the average for 1979–2010, particularly in western and north-western Greenland (see Figure 7).

The rate of Greenland melt – along with that of Antarctic ice-shelves – is one of the key drivers of global sea-level rise. The influx of increased amounts of freshwater into the North Atlantic, meanwhile, could have broader consequences for heat carried by ocean currents which, in turn, could have consequences for weather patterns. And, although very far from immediate, there may be thresholds for the irreversibility of the decline of the Greenland ice sheet, meaning the original ice sheet volume could only be regained if the losses were no greater than 10–20%⁵ .

Figure 7: 2011 deviation from mean number of melt days on Greenland over the period 1979-2010

Footnotes: 

(xiii) The melting of floating sea ice has no direct impact on sea level when it melts because the displacement of sea is the same whether the water is in a liquid or frozen state.

Charles Emmerson, Glada Lahn, 2012, Global Consequences of Arctic Environmental Change, Lloyd’s.©