CATHOLIC NEWS OF THE WEEK . Saturday, 17 November 2018

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The oceans may produce more than a high tide

In recent years, we have become more and more aware of how vulnerable our oceans are to climate change. The Arctic Ocean is capped by frozen seawater, called sea ice. This melts during the Northern Hemisphere spring and summer months.

It normally reaches its minimum extent in mid-to-late September before refreezing. Since 1978, satellites have monitored the melting and freezing of sea ice. They have detected an overall decline in Arctic sea ice coverage by almost 12 per cent per decade.

This means that the Arctic Sea will be ice free by 2030. The reason is that the temperature in the Arctic has increased at twice the rate of the rest of the world and could possibly increase by another eight degrees Celsius by 2100. Many species, especially polar bears, will be adversely affected by the dwindling ice cover.

There is also the possibility that it will weaken or shut-down completely the global ocean circulation, because as ice forms, it expels the salt which increases the density of the surrounding water and, as a consequence, play a crucial role in global ocean circulation.

The shutting down of the Gulf Stream would have a huge impact on the climate of western and northern Europe, especially Ireland and Britain.

The mass of the Greenland ice sheet has been rapidly declining in recent years, due mainly to surface melting and iceberg calving. 

Research based on data from National Aeronautics and Space Administration’s (NASA) twin Gravity Recovery and Climate Experiment (GRACE) satellites, indicates that between 2003 and 2013, Greenland shed approximately 280 gigatons of ice per year, causing global sea level to rise by 0.8 millimetres annually.

In general, in the interior of Greenland there has not been much change, but in the southern coastal area, up to three metres of ice mass has been lost over a period of 10 years during which these observations took place. The largest loss of up to 30 centimetres per year occurred over southern Greenland.

NASA’s GRACE has also produced quite worrying data from the Antarctic. In the 10-year period between 2003 and 2013, the Antarctic lost 90 gigatons of ice per year. This caused global sea-levels to rise by 0.25 millimetres annually.

Glaciers are also on the move in Antarctica. The highly dynamic Pine Island Glacier, which is located in the western Antarctic, is, in fact, a large ice stream. In other words, it is moving faster than the surrounding ice.

Satellite data shows that the speed of this glacier has increased dramatically from the late 1990s until the present. On 26 October 2011, NASA’s Operation IceBridge campaign made the first detailed measurements of a major iceberg calving event, which took place on the Pine Island Glacier.

The depth of the canyon which was created was between 50 and 60 metres and an average of 73 metres wide, which made it possible to fly through the ice canyon.

If these changes continue or increase, the rise in sea-levels will exceed the projected one-metre rise by the end of this century. This will have enormous consequences for all coastal cities, which will be highly vulnerable to storm surges and serious flooding.

 

• Father Sean McDonagh

 

(All the data used in this article is taken from the US Centre 2014 Hyperwall Science Stories, which was distributed during a seminar at the US Pavilion in Lima on