If the earth is signalling the beginning of some major consequences of climate change – and I believe it is – are we really listening, and then acting? The Independent reports and gives its opinion…
‘Emergencies around the world are grabbing our attention and prompting action from our political leaders. The nuclear crisis in Japan has galvanised governments, from China to Germany, to review their own nuclear power programmes. The threatened humanitarian disasters in Libya and Ivory Coast have prompted military interventions from Nato and the United Nations. But when it comes to the most pressing international emergency of all, the destabilisation of the planet’s climate through mankind’s emissions of carbon dioxide and other industrial gasses, all urgency has drained away.’
Scientists have identified a massive volume of freshwater floating like a cap on the Arctic Ocean, which they believe could suddenly flow into the North Atlantic and affect the warm Gulf Stream that keeps Britain mild in winter and cool in summer.
Studies have shown that a surface layer of fresher water in the Arctic Ocean has increased in volume by about 20 per cent over the past two decades. Scientists believe this is the result of melting sea ice and an increased flow of rivers from Siberia and Canada carrying large volumes of meltwater from permafrost regions.
In the Canada Basin area of the Arctic to the west of Greenland, for instance, scientists are monitoring a huge pool of icy meltwater more than 7,500 cubic kilometres in size, which is about twice the volume of Africa’s Lake Victoria. This pool of cold freshwater, which is less dense than the saltier seawater on which it floats, is being kept in its place by circulating winds.
The scientists are concerned that a sudden change in wind patterns might send this fresher water south via the Labrador Current into the North Atlantic where it could interfere with the complex “thermohaline” ocean circulation. These currents, which keep the warm Gulf Stream flowing towards Britain and the rest of north-west Europe, flow between the sea surface and the seabed and are controlled by the relative saltiness of seawater.
“In the past we know that a sudden change in Atlantic currents has happened because of a relatively sudden release of freshwater into the North Atlantic. We can imagine that it could happen again,” said Benjamin Rabe, of Germany’s Alfred Wegener Institute for Polar and Marine Research in Bremerhaven.
“If that amount of freshwater is going to be suddenly released it would influence ocean currents, for instance the thermohaline circulation of the North Atlantic. I think we should definitely look at this further. The thermohaline ocean current has only been monitored for a few years,” he added.
Scientists from 17 research institutes in 10 European countries have collaborated as a consortium known as CLAMER in documenting the build-up of fresher water in the Arctic. One of the techniques involves sending salinity gauges down to different depths of the sea from the RV Polarstern ice-breaker, a German research ship.
The scientists have collated about 5,000 salinity profiles of the Arctic and estimated a 20 per cent increase in freshwater over the entire region since the early 1990s, when measurements of this type began. This corresponds to a rise of some 8,400 cubic kilometres of freshwater over this period, which is roughly equivalent to the entire volume of freshwater and ice that is released each year from the Arctic into lower latitudes.
Laura de Steur, an oceanographer from the Royal Netherlands Institute for Sea Research, said that for the past 12 years a mostly clockwise pattern of winds has kept a huge volume of this fresher water within the Canada Basin. This body of relatively salt-free water has probably resulted from increased river run-off and melting ice, she said. “The volume of water discharged into the Arctic Ocean, largely from Canadian and Siberian rivers, is higher than usual due to warmer temperatures in the north causing ice to melt. Sea ice is also melting quickly, adding even more freshwater to the relatively calm Arctic Ocean,” Dr de Steur said.
“In addition, sea ice that is thinner is more mobile and could exit the Arctic faster. In the worst case, these Arctic outflow surges can significantly change the densities of marine surface waters in the extreme North Atlantic. What happens then is hard to predict,” she added.
John Toole, of the Woods Hole Oceanographic Institution in Massachusetts, said that when seawater gets as cold as it does in the Arctic region, salinity becomes a crucial factor in determining whether water floats near the surface or sinks deeper. This is critical in terms of what drives the pump of the thermohaline ocean circulation.
“There is a suspicion that if the Arctic continues to store up low-salinity surface water, it’s just a matter of time before it ships it further south and into the North Atlantic where it may impact the intensity of the thermohaline circulation. This is what happens when we simulate this in computer models,” Dr Toole said.
“What we are seeing is a build-up of fresher water in the Arctic and that this build-up of liquid freshwater is bigger than we’ve seen over the instrumental records which extends over several decades. It’s difficult to say what the consequences of that may be,” he added.
However, one scenario depicted in the Hollywood movie The Day After Tomorrow, in which the Gulf Stream is turned off, causing a sudden ice age in New York, is firmly discounted by the scientists. Dr de Steur said: “Ice ages occur on geological time-scales of tens of thousands of years. However, large regional changes could be in store if the ocean circulation changes.”
Steve Connor: We may be on the brink of major instability
Decent science fiction has more than a grain of truth to it. So it was with The Day After Tomorrow, the movie that brought the esoteric science of ocean currents to cinema audiences. But the fantastical plot behind the film contained only a tiny grain of truth in a whole sackful of Hollywood hype.
As anyone who has done basic geography should know, we in Britain live at the same latitude as Newfoundland, yet we enjoy a much milder climate thanks to the heat brought to us by the Gulf Stream, or more accurately, the North Atlantic Drift. Newfoundland, meanwhile, bathes in the icy Labrador Current. It is estimated the Gulf Stream’s heat content is equivalent to the output of about a million power stations.
If this vital ocean current were to slow down or shut off completely, we would feel a lot colder in winter, with our ports and shores icing up as they do in Newfoundland. The pump that drives this ocean current, or at least a major part of it, is known as the thermohaline circulation. This ocean current is dependent on both heat and the salinity of sea water, so anything that affects either has the potential to upset the pump that moderates our climate.
About 13,000 years ago, after the last ice age, it was thought that this actually happened when a huge volume of fresh water flowed relatively quickly from the melting ice sheet of North America into the North Atlantic. It is thought that the sudden flow of huge volumes of fresh water disturbed the salty pump behind the warm ocean currents of the North Atlantic.
What is going on now in the Arctic appears to be small beer by comparison. The volumes of fresh water building up on the surface of the Arctic Ocean are tiny compared with the really massive amounts of meltwater that flowed from the ancient glacial Lake Agassiz of North America, which is estimated to have contained more fresh water than all the lakes of the world combined.
Yet, from what the experts are telling us, there is some cause for concern. We may be witnessing a further climatic change in the Arctic that could become unstable. It needs to be monitored closely if we are to understand its significance.
Our response to climate change should be as urgent as it is to crises in Libya and Ivory Coast