This is controversial, but there is growing scientific research backing the still contested conclusion that changes to the Arctic are leading to changes in weather in the mid-latitudes. The basic idea is that a warmer Arctic plays games with the jet stream, the stream of air high above us in the stratosphere that carries our weather and that is driven by temperature contrasts between the mid and high latitudes.
If the Arctic warms faster than the mid latitudes do, then the jet stream could slow down, goes the theory. It could develop a more elongated and loopier path, leading to a persistence of particular weather conditions - whether intense snow, intense heat, intense rain, or something else that is, you guessed it, intense.
A recent study published in the journal Science found that a more wavy and elongated jet stream in the summer "has made weather more persistent and hence favoured the occurrence of prolonged heat extremes".
The National Research Council handles the controversy over this idea by simply stating that "some scientists" have suggested these changes to the jet stream are happening. For now, we'll simply have to watch closely as the debate over this idea continues.
2. Changing What You Eat
The National Research Council booklet also notes that warming oceans could have a substantial effect on the fishing industry, which prowls the Arctic and sub-Arctic for a crucial part of its catch. "About half of the US fish catch comes from subarctic waters," notes the report.
Fishermen and fishing boats may have new routes open to them due to a less icy Arctic, the report acknowledges. But at the same time, the composition and distribution of species could change with warming waters:
"Atlantic cod, for example, have been displacing the endemic polar cod in the waters surrounding the Norwegian archipelago Svalbard. In addition, rising temperatures and an influx of fresh water from melting ice can cause rippling effects through the marine food chain. In the North Atlantic, for example, scientists project that ocean warming will cause shifts in the spawning and feeding grounds of several economically important fish populations, including Arctic cod, herring, and capelin."
Granted, we shouldn't be alarmist about this. Contrary to a number of press accounts, global warming is not going to take away your fish and chips.
3. Raising Sea Levels
The melting of ice on land in the Arctic - whether from glaciers and ice caps in the Arctic, or the Greenland ice sheet - contributes to sea level rise that does not stay in the Arctic, but rather spreads around the world. Greenland is of course the biggest potential contributor, since if it were to melt entirely, it would cause 6m of sea level rise.
And there's also a less known Arctic contributor to sea level changes: the way polar melting could weaken the great overturning circulation of the oceans.
There is suggestive evidence that the melting of Greenland is already contributing to a freshening of the waters of the north Atlantic. This, in turn, may be slowing down the so-called Atlantic meridional overturning circulation - which carries a tremendous amount of warm water northward in the Atlantic.
If the circulation weakens, then it affects sea level on either side of it. That's for two reasons: Warmer waters lie to the right or east of the Gulf Stream, and warm water expands and takes up more area - leaving sea level lower on the US coast side of the circulation. A weakening would thus raise sea levels in the US.
There's also the fact that in the Northern Hemisphere, "sea surface slope perpendicular to any current flow, like the Gulf Stream, has a higher sea level on its right-hand side, and the lower sea level on the left-hand slide," according to Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research. So again, a weaker Gulf Stream evens that out, and you'd see sea level rise on the US coast.
4. Worsening Global Warming Itself
Finally, changes in the Arctic are expected to amplify global warming itself. The principal way this could happen is through the thawing of frozen ground or permafrost, which covers much of the Arctic, and which contains huge stores of frozen carbon.
Recent scientific analysis has affirmed that Arctic permafrost is packed with carbon - some 1330 and 1580 gigatons worth, and that may be a low end estimate - and that over the course of the century, a substantial fraction will get released to the atmosphere. It would probably happen slowly and steadily, but it could amount to a significant contribution to overall global warming.
Why will this occur? As the National Research Council explains:
"Plants are essentially made of carbon. When a plant dies in a temperate area, it decomposes, releasing some of its carbon into the air and some into the soil. But when a plant dies in a place too cold for decomposition, it simply stays put, locking its carbon in place."
Until permafrost thaws, anyway. If enough of it does so, the volume of carbon emissions could be enough to set back worldwide efforts to reduce emissions from fossil fuel burning by adding an entire new source of greenhouse gases beyond the usual suspects, like fossil fuels and deforestation.
Last month, when we learned that Arctic sea ice had reached a record winter low, former Deputy Assistant Secretary of State Rafe Pomerance said: "The Arctic is unravelling, warming twice as fast as the rest of the planet." It's a powerful quotation, and as the US takes chairmanship of the Arctic Council on April 24, you shouldn't assume that "unravelling" is irrelevant to you. We're all invested in the Arctic, because we're all invested in the planet.
- Washington Post
