The Arctic, Antarctic and high latitudes have had the highest rates of warming, and this trend is projected to continue, as the above-mentioned Global Biodiversity Outlook 3 notes (p. 56).
In the Arctic, it is not just a reduction in the extent of sea ice, but its thickness and age. Less ice means less reflective surface meaning more rapid melting. The rapid reduction exceeds even scientific forecasts and is discussed further on this site’s climate change introduction.
The polar bear depends on sea ice. (Image source)
In terms of biodiversity, “the prospect of ice-free summers in the Arctic Ocean implies the loss of an entire biome”, the Global Biodiversity Outlook notes (p. 57).
In addition, “Whole species assemblages are adapted to life on top of or under ice — from the algae that grow on the underside of multi-year ice, forming up to 25% of the Arctic Ocean’s primary production, to the invertebrates, birds, fish and marine mammals further up the food chain.” The iconic polar bear at the top of that food chain is therefore not the only species at risk even though it may get more media attention.
Note, the ice in the Arctic does thaw and refreeze each year, but it is that pattern which has changed a lot in recent years as shown by this graph:
The extent of floating sea ice in the Arctic Ocean, as measured at its annual minimum in September, showed a steady decline between 1980 and 2009.Source: National Snow and Ice Data Center, graph compiled by Secretariat of the Convention on Biological Diversity (2010) Global Biodiversity Outlook 3, May 2010
It is also important to note that loss of sea ice has implications on biodiversity beyond the Arctic, as the Global Biodiversity Outlook report also summarizes:
- Bright white ice reflects sunlight.
- When it is replaced by darker water, the ocean and the air heat much faster, a feedback that accelerates ice melt and heating of surface air inland, with resultant loss of tundra.
- Less sea ice leads to changes in seawater temperature and salinity, leading to changes in primary productivity and species composition of plankton and fish, as well as large-scale changes in ocean circulation, affecting biodiversity well beyond the Arctic.
— Secretariat of the Convention on Biological Diversity (2010), Global Biodiversity Outlook 3, May, 2010, p.57