Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 286

9

8

7

6

5

4

3

2

1

0

1980 1985 1990 1995 2000 2005 2010

Year

Fig. 6.3 ExtentoftheminimumArcticseaiceattheendofthesummer(September).BasedondatafromtheNational

SnowandIceDataCenter(US)attheUniversityofColorado(http://nsidc.org).Arcticseaiceextenthasbeen
measuredbysatellitemicrowaveremotesensingsince1979.TheEarth'ssurfaceismeasureddividedupinto
cellsaround25km

25km.Atleast15%ofacell'sareahastohaveiceforittobedeinedasice-covered.The
1979-2000meanminimumsummerArcticsea-iceextentwas7.7millionkm 2 .The1979-2000mean
thereforegivesalong-termtrendvalue(asopposedtoactualvalue)for1990,theyearoftheirstIPCCreport
andabaselineyearformuchclimatechangepolicy.

×

that declines in Antarctic krill ( Euphausia superba ) - which form much of the
emperor penguin diet, along with fish and squid - may be linked to this decline in
the emperor penguin population. Krill also sustain a number of commercial fisheries
and concomitantly are fundamental to much of the Antarctic marine food web and
populations. Yet lower krill abundance is associated with less winter ice. That krill
populations around the Antarctic are changing with warming waters, and changes in
sea ice, as well as commercial fishing (see Schiermeier, 2010), have been corrob-
orated by a body of research. For example, in 2004 a research team, led by Angus
Atkinson of the British Antarctic Survey, reported that between 1976 and 2003 the
Antarctic south-west Atlantic sector, which contains over half of Southern Ocean
krill stocks, saw stock densities decline by more than 50%, while elsewhere those of
salps (mainly Salpa thompsoni ) increased. This represents a profound change in the
Southern Ocean food web.
Looking briefly at the marine environment on the global scale, the question of
disentangling the impact of commercial fisheries and that of climate change on krill
stocks brings us to a key problem for ecologists: is it non-climate-related human
activities (such as fishing and pollution) and/or climate change having an impact at
the global scale? In 2010 Ove Hoegh-Guldberg and John Bruno from the University
of Queensland in Australia, and the University of North Carolina at Chapel Hill,