By Paul Homewood
Today's climate scare comes from the BBC:
A keystone prey species in the Southern Ocean is retreating towards the Antarctic because of climate change.
Krill are small, shrimp-like creatures that swarm in vast numbers and form a major part of the diets of whales, penguins, seabirds, seals and fish.
Scientists say warming conditions in recent decades have led to the krill contracting poleward.
If the shift is maintained, it will have negative ecosystem impacts, they warn.
Already there is some evidence that macaroni penguins and fur seals may be finding it harder to get enough of the krill to support their populations.
"Our results suggest that over the past 40 years, the amount of krill has, on average, gone down, and also the location of the krill has contracted to much less of the habitat. That suggests all these other animals that eat krill will face much more intense competition with each other for this important food resource," Simeon Hill from the British Antarctic Survey told BBC News.
It focuses on the Scotia Sea and the Antarctic Peninsula – the places where the crustaceans are most abundant.
Scientists have been gathering data in these areas since the 1920s.
Initially, krill catches were recorded to understand the environmental consequences of commercial whaling, but the information has continued to be collected through to the present.
Dr Hill and colleagues say the change in the distribution and density of the crustaceans is a clear signal that emerges in the data from the late 1980s onwards.
It coincides with a phase change in a climate oscillation known as the Southern Annular Mode.
The SAM essentially describes the dominant pattern of pressure zones in the southern hemisphere outside of the tropics.
The mode's switch in state in the late 80s produced warmer, cloudier, windier weather, and much less sea-ice in those areas where the krill had tended to congregate.
https://www.bbc.co.uk/news/science-environment-46953652
Note to the BBC – the Southern Annular Mode (SAM) has nothing whatsoever to do with climate change. Instead it is simply a natural climatic cycle, just as the PDO or AMO are.
New Zealand's Environmental Reporting Series shows how the SAM has oscillated since the 1800s:
The population of krill has been affected by other factors over the decades.
When commercial whaling was large scale in the early years of the 20thC, the population of krill would naturally have thrived.
Just at the time when whaling was ending, fishing for krill took off. According to this 2014 paper:
Fishing is the major industry in Antarctic waters. Hundreds of thousands of tons are landed each year. Antarctic krill (E. superba) support the largest fishery (Figures 5 and 6). In the 1970s, development of the commercial krill fishery was facilitated by heavy fishing subsidies in the USSR, which became the most important krill-fishing nation during the 1970s and the 1980s (Nicol and Foster, 2003).
https://academic.oup.com/icesjms/article/71/7/1934/666832
FAOSTAT show how the harvest of Antarctic krill grew from a figure of 4t in 1961 to over 500,000t. Even though harvest dropped back in the 1990s, the damage had already been done.
http://www.fao.org/fishery/species/3393/en
Most of the fishing takes place in the Scotia Sea, which this new study has identified as the main area of decline.
According to the BBC article:
Margaret McBride, from the Norwegian Institute of Marine Research in Bergen, has written a comment article on the research in the same edition of Nature Climate Change.
She said models had predicted that krill would shift southwards in the future, whereas the new research suggested this contraction was already under way.
"It offers a profoundly adverse, but highly plausible, endgame for Antarctic krill that has serious implications for both the Southern Ocean food web and sustainable management of fisheries targeting this species," she wrote
However, although the actual study makes vague warnings about what a warmer climate might bring in future, it provides no evidence that global warming has had any effect on the current situation.
Indeed, on the contrary Southern Ocean SSTs have been dropping since 1980, and currently are below the long term mean.
https://bobtisdale.wordpress.com/2016/11/08/october-2016-sea-surface-temperature-sst-anomaly-update/
It has also been claimed that krill are at risk from winter sea ice recedes. But as we know, winter sea ice extent has been gradually rising since 1979:
https://nsidc.org/data/seaice_index/bist
There is no evidence in this study to show that the population or distribution of Antarctic krill has been affected by global warming, or will be in future.
from Climate Change Skeptic Blogs via hj on Inoreader http://bit.ly/2FTqFeG
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