ENVIRONMENT by Peter WestmoreNews Weekly
Ignore claims that Antarctic ice sheet will melt away
, March 11, 2017
Last December and again last month, climate scientists warned of the imminent danger of the melting of the Antarctic ice sheet as a result of global warming.
In December, Dr Steve Rintoul was reported to have said that the Totten Glacier (pictured) in Eastern Antarctica was melting because of climate change.
The Totten Glacier.
Radio NZ reported that Dr Rintoul was deeply concerned over the event.
“We thought that East Antarctica was pretty much isolated from those warm waters and therefore was likely to be more stable,” he said.
“The satellite data showed that maybe that’s not quite the case, and our expedition – the first to actually get a ship to the front of the Totten Glacier – showed that just like in West Antarctica the water is driving melting of these ice shelves from below.”
Dr Rintoul said that if the vast Totten Glacier melted entirely, it would raise the world’s sea level by about 3.5 metres.
Dr Rintoul was a lead author of the Oceans chapter in the IPCC’s fifth Assessment Report.
Separately, a British team headed by Professor Adrian Luckman told the BBC that he expected the Larsen C Ice Shelf to split off, forming a massive iceberg of 5,000 square kilometres, a quarter the size of Wales.
A long rift had developed in the ice shelf over recent years, but its progress had recently accelerated, with an 18-kilometre increase last December. Now, just 20 kilometres of ice is still attached to the continent.
The BBC said that the latest event followed the earlier calving of the Larsen A and Larsen B ice shelves.
“It is believed that climate warming has brought forward the likely separation of the iceberg, but the scientists say they have no direct evidence to support this,” it said.
Both reports made alarming claims of imminent and extreme change to Antarctica, and left the impression that this was caused by global warming. But is this true?
One reason we know more about events in Antarctica is that there are now more scientists visiting the frozen continent than ever before.
Another important fact is that scientists now have access to satellite images of the Antarctic region, allowing daily maps to be drawn of the extent of sea ice around the continent.
In fact, the information showing the lengthening crack in the Larsen C Ice Shelf came directly from satellite images.
Despite the alarmist reports, the area of sea ice around the Antarctic continent shows no discernible long-term trend over the past 35 years – the period for which satellite observations have been made.
True, there have been periods of rising and falling sea-ice extent, some that are large seasonal variations from summer to winter, but there is no clear overall trend.
In light of this, claims that observed changes in the Antarctic sea ice are caused by climate change are at best purely speculative, and at worst, alarmist propaganda.
There are other reasons to be cautious about attributing any change to global warming.
The first is that the calving of glaciers is an entirely natural event. Glaciers are rivers of ice that flow into the sea. At the point where the ice meets the sea, relentless pressure forces the ice flow out into the sea where it naturally melts and eventually breaks off.
An additional point of importance is that ice shelves are small mountains of brittle ice, and float on the seawater, which is subject to tidal forces. At the Australian bases in Antarctica, the tidal variation is around 1.8 metres. As the sea ice stretches out into the sea, the ice shelf is being bent up and down until it eventually breaks.
Many years ago, icebergs were observed floating north past the south island of New Zealand. At the time, no one knew exactly where they had come from, but they were clearly the result of a major carving event on Antarctica.
There are other factors at play.
Unlike the Arctic region, where the North Pole is located in the middle of the Arctic Sea, Antarctica is a continent, covered by ice thousands of metres thick.
Across Antarctica, there is a constant and powerful westerly wind, which is also believed to be the cause of the wide Antarctic Circumpolar Current, the strongest ocean current in the world, which for most of its course is thousands of kilometres wide and revolves endlessly around Antarctica.
This current is the source of the cold current that runs up the west coast of Western Australia.
Because of its width, the Antarctic Circumpolar Current effectively separates the Antarctic continent from the rest of the world’s atmosphere, making the far southern latitudes much colder than those in the northern hemisphere, and less affected by climate change.
Another factor that could account for the warmer waters near Antarctica is the presence of sub-sea volcanoes, of which little is known. Contrary to most expectations, Antarctica is geologically active, and Australia’s only active volcano is to be found on Heard Island, far south of Hobart.