Decreasing Arctic Sea Ice

Monthly November Arctic ice extent for 1979 to 2016, showing a decline of 5.0 percent per decade © NSIDC

Monthly November Arctic ice extent for 1979 to 2016, showing a decline of 5.0 percent per decade © NSIDC

The loss of Arctic sea ice impacts marine mammals directly through loss of habitat and decrease in habitat quality for ice breeding species. The dramatic shrinking of the ice cover and changing in ice freezing patterns both alter animal distribution and migration routes.

Marine mammals will also be affected indirectly through changes in prey abundance and distribution, top predator communities and food chain dynamics. Some species / food sources will disappear, move to different location or become available at different times, sometimes too late or too early for coinciding with the predators’ maximum needs. The impact will be cascading in the food chain, starting at the level of micro-organisms (ice biota and plankton) through invertebrates and fish communities to top predators – birds and mammals.

The dramatic shrinking of the ice cover and the changing ice freezing patterns not only alter animal distribution and migration routes but also the accessibility to resources, making hunting harder.

Business as usual? — One key difference between the temperature spikes 20 or 30 years ago and now is the fact that Arctic sea ice has become much weaker and thinner over the past two decades. It has become much less resilient, which makes it more difficult for it to withstand unusual weather events. Thicker multiyear ice is less affected by unusual weather patterns such as strong winds or warmer temperatures. It acts like a glue, holding together the ice, especially at the end of the summer when all the younger and weaker ice has melted. But multiyear ice is now virtually gone and only accounts for three percent of ice in the Arctic Ocean, compared to 20 percent in the 1980s.

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