


Investigating critical thickness of sea ice

Canterbury researchers investigating critical thickness of sea ice

April 1, 2014

University of Canterbury researchers are investigating key factors into the state of the climate system by assessing sea ice thickness in the Southern Ocean.

University postgraduate student Daniel Price is investigating the thickness of the sea ice in the Antarctic which is a key part of the Earth’s climate system.

Sea ice forms in the polar oceans where low air temperatures permit the ocean surface to reach its freezing temperature of around -1.9C.

The polar regions are vital components of the global climate system as drivers and indicators of change. It is highly reflective and immediately sends the majority of sunlight back into space, Price says.

``If it were not there, that energy would be absorbed by the ocean. In the Arctic, the sea ice’s minimum extent has decreased by 12 percent per decade since the late 1970s.

`` Contrary to the Arctic, the Antarctic sea ice extent has undergone a slight increase. This is a paradox in a warming world and a topic of intense scientific debate. Currently two main possible explanations exist.

``The first describes a process by which melt water from glaciers on the Antarctic continent is increasing in the Southern Ocean due to warming, decreasing salinity and making it easier for sea ice to form. The second is related to changing wind patterns around Antarctica as the ozone hole slowly repairs itself.

``The climate system is complex and the fact that sea ice has slightly increased in the Antarctic is certainly not evidence against human-driven climate change.

``In the Southern Ocean sea ice grows and then melts almost completely away every year. At its annual maximum extent in September, around the Antarctic continent, it covers an area of 19 million square kilometre, slightly larger than Russia.

``Though the size of the sea ice area is well documented, its thickness in the Southern Ocean is not. Given the vast area which needs to be investigated satellites offer an opportunity.

``Using radars and lasers on board NASA and European Space Agency satellites, orbiting the Earth 700 kilometres above the surface, we are able to indirectly estimate the thickness from the bit of ice that sticks out above the surface of the ocean.

``These satellites are capable of measuring to centimetre accuracy. The development and improvement of these techniques is my topic of research here at the University of Canterbury.

``Changes to sea ice may be influential on weather patterns in the Southern Ocean and therefore on New Zealand. It is thought that recent disruptive weather events in Europe and North America could be linked to sea ice decline in the Arctic.’’

The assessment of sea ice thickness in the Southern Ocean on a large scale is an international environmental science priority as indicated in the major Intergovernmental Panel on Climate Changes Report.

University of Canterbury’s Gateway Antarctica forms a small component of this international effort involving collaborators at NASA, Alfred Wegner Institute, Germany, York University and the University of Alberta, Canada and the University of Otago.


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