Arctic sea ice reached a record low of 3.42 million square kilometres on September 16, 2012, surpassing by 18 percent the record set in 2007 of 4.17 million square kilometres. And this 2007 record surpassed the previous 2005 record by 22 percent. Dr. Walt Meier of the National Snow and Ice Data Center in Boulder, Colorado, summarizes the events this way: “On top of that [2012 record], we’re smashing a record that smashed a record” (Globe and Mail, Sept. 20/12). To set this in perspective, the Arctic’s summer sea ice in the 1980s covered an area slightly smaller than the mainland United States; now it covers half that area.

Adding to Dr. Meier’s statement is a comment from his colleague, Dr. Mark Serreze. “Recently the loss of summer ice has accelerated and the six lowest September ice extents have all been in the past six years. I think that’s quite remarkable” (Ibid.). With the exception of one “strong storm”, all this melt has been due to the day-by-day effects of a warming planet. As Dr. Jason Box of Ohio State University notes, “Arctic sea ice is one of the most sensitive of nature’s thermometers”(Ibid.).

As the Arctic’s temperature goes up, the effects are felt directly in the Arctic landscape. The increasing warmth melts permafrost so roads sink, building foundations collapse , shoreline settlements slough into the sea, while trees and power poles tilt helter-skelter as their footings soften. Except for the release of methane, these are incidental micro effects of relatively little environmental significance.

Even the geo-political complications of newly opened international shipping routes through melted Arctic waters are of minor importance. Canada’s jurisdictional disputes with China, Russia and the United States about authority over these passages will simmer more actively as the ice retreats even further. Many of these marine routes are still uncharted so vessels risk grounding or sinking. Oil spills become a constant worry in the pristine Arctic waters. Drilling for petroleum and gas resources becomes a contentious subject that didn’t exist before the sea ice began melting.

The more serious effects, however, are macro. Sea ice reflects about 90 percent of the sun’s heat — the so-called albedo effect that helps to cool both the Arctic and the planet. Without sea ice, about 50 percent of this heat is absorbed by the dark water that replaces it, a process that accelerates the effects of global warming and explains why the Arctic is warming at about twice the rate of the rest of the planet. In a positive feedback loop, the increasing areas of open water absorb even more heat, that melts even more ice, that raises the temperature even higher, that causes even more ice to melt. And the implications are not just local but global.

A warmer Arctic means that the temperature differential between northern and southern latitudes is reduced. And this has direct effects on both climate and weather.

The ocean currents that distribute heat around the planet are driven by the simple physical principle that cold water is heavier than warm water. Tropical water flows northward on the surface, bringing heat to northern latitudes. It then cools, sinks and carries cool water southward along the ocean’s bottom to alleviate high temperatures in the tropics. Global weather patterns are partly determined by this movement of ocean water. As Arctic waters warm, they are less inclined to sink, the convection currents slow, and the planet’s weather changes.

Melting Arctic sea ice has another macro effect. Jet streams, the high elevation winds that mix air around the planet, are affected by Arctic temperatures. When the temperature differential between high and low latitudes is relatively large, the jet streams tend to be more active, drifting north and south more vigorously and shifting weather with them. With a lower temperature differential, the jet streams tend to be less active, thereby locking weather patterns in place for protracted periods. This may explain why droughts tend to be more persistent and wet periods tend to be longer. It may also explain why the summer of 2012 brought record rainfall to the East Coast of Canada and record dry spells to the West Coast. Wildfires, crop failures, dried rivers, and floods are more likely when weather patterns are locked in place by stalled jet streams.

A warmer Arctic from melted Arctic ice also means higher humidity in the higher latitudes. The dry air of the northern desert becomes wetter. When this air is pulled southward by winter storms, the result is more rain and snow for lower latitudes. This dynamic may account for some of the extreme rain and snowfall of recent winters.

Weather, of course, is extremely complicated. But the changes occurring around the planet are supported by current data and are consistent with the most advanced computer modelling at our disposal. And Arctic sea ice is a significant factor in this complex matter.Alter it and everything else changes. We, too, are affected because we have built our cities, farms, industries and global systems upon a presumption of predictable weather. Agricultural crops are totally dependent on climate normality. Harvest failures affect food prices and economic stability, even reverberating into political security — the so-called Arab Spring that rocked Tunisia, Libya, Egypt and now Syria was triggered by food shortages caused by weather anomalies.

As climatologists have noted, the greatest experiment being conducted on the planet these days is not our search for the elusive Higgs boson at the multi-billion dollar Large Hadron Collider in Switzerland. Rather, it is our experiment with global climate and weather, conducted by the massive amounts of carbon dioxide we are emitting from burning fossil fuels. Melting Arctic sea ice is just one disruptive consequences of this huge, uncontrolled experiment.