/ 28 November 2016

Arctic melt threatens to unravel global climate

A polar bear at the Arctic Ocean
A polar bear at the Arctic Ocean

The Arctic didn’t quite break its record for low ice cover this nothern summer. It came second. But temperatures on that top part of the world have been breaking all sorts of records since then. Air temperatures are 20°C higher than they should be in November – it’s normally -25°C at this time of year and now it’s hovering around freezing point. Sea temperatures in the Arctic Ocean are also 4°C higher than normal. Oceanographic and atmospheric organisations say this is stopping new ice from forming. That will probably lead to record low ice cover in the Arctic next summer.

The dangers of this continuing reduction in ice cover were explored in this year’s Arctic Resilience Report. The report is the culmination of five years of research by the Stockholm Environment Institute and the Stockholm Resilience Centre.

It noted that while “life in the Arctic has always been defined by change and uncertainty”, that change was happening quicker than ever before. “The Arctic is now changing at an unprecedented pace, on multiple levels, in ways that fundamentally affect both people and ecosystems.” That change is happening in a variety of ways, from coastal areas eroding with higher sea levels to melting ice and permafrost thawing.

The Arctic is important because it reflects a lot of the sun’s radiation back into space. That helps regulate the planet. The cold ice also plays a critical role in cooling the ocean and wind currents that blow and flow through it. This balances out the warm water and air that comes from the same currents as they flow through the tropics.

When the ice melts, it leaves large parts of ocean that no longer reflect the sun. Instead, it absorbs heat and warms the water around it.

The Resilience report said this starts a dangerous cycle. Once a certain amount of ice is lost, more water is uncovered which then absorbs heat, which creates more warming and melts more ice. The whole Arctic then gets stuck in a spiral of melting and warming.

That spiral is known as a positive feedback loop, where one change creates and accelerates other changes. Ecosystems start to unravel, driving other ecosystems that rely on them to unravel. So fish that have adapted to cold water migrate or die out, which means there isn’t food for large predators such as polar bears.

The report said the effects of these changes in the Arctic will have “substantial” impacts on the rest of the world. With a global climate system that is always struggling to reach some sort of equilibrium, changes far away can trickle across the globe. The butterfly effect on a mega-scale.

Some of the changes in the Arctic are straightforward. The Greenland ice sheet usually takes thousands of years to respond to the changing climate, but in the last few years its ice has started to thin away. That melt trickles through the ice sheet and creates cracks that expose more parts of the sheet to heat. The warmer ocean also nibbles away at the edges of the ice sheet. If the whole ice sheet melts, it will raise global sea levels by an average of 7.4-metres. Not good for South Africa’s coastal cities.

The same works for the drop in ice cover across northern Russia and Canada. Less snow and warmer temperatures mean more plants growing, which absorb heat instead of reflecting it. That means more warming and more ice melting, which releases methane – one of the most potent greenhouse gases of all.

What happens next it too unpredictable to compute. For South Africa, research by the environmental department shows that the high pressure systems which bring rainfall will move further away with warming oceans. That will mean less rain – but heavier bouts of rain.

What is certain, and what the report warns of, is that global change is happening thanks to a warming Arctic and that at too quick a rate for plants and animals to adapt.