Primary Arctic productivity continues despite warmer temperatures

Written by Dr Susan Crockford on December 16, 2022. Posted in Current News

NOAAs annual Arctic Report Card is, for the most part, a valiant effort to turn good and ambiguous news into harbingers of climate disaster

Primary productivity is up across most of the region (good news for wildlife) and despite Arctic temperatures being “twice as high” as the rest of the world in recent years, the summer sea ice ‘death spiral’ has failed to materialize.

Oddly, there is no bad news about polar bears (last mention was 2014).

However, the media were told that the few hundred sea birds that died this year in the enormous Bering/Chukchi Sea region over the four months of summer in 2022 is a portend of climate change catastrophe–even though the authors of the NOAA report admit they have no conclusive evidence to explain the phenomenon.

However, here are also some honest figures that are quite illuminating.

Sea ice

The graph at the bottom of this graphic, spread out rather than bunched up to make changes seem more dramatic, makes it much easier to see the lack of a declining trend in sea ice extent since 2007, and that winter (March) coverage has changed hardly at all.

Arctic temperatures

Compare the graph of overall Arctic temperature in this composite to the sea ice graph above: note the lack of correspondence between average temperature and sea ice extent since 2007.

Loss of multiyear ice

The essay by Meier and colleagues also includes an interesting graphic, showing changes in multiyear ice over time since 1984.

Note that multiyear ice is unproductive habitat as far as marine organisms are concerned: first year (seasonal) ice over continental shelves are the the most productive and thus where the vast majority of polar bears, seals, fish, whales, and sea birds are found.

I don’t see much reason to mourn the decline of extremely thick multiyear ice (>4 years old, red line in the graph below) as far as wildlife is concerned, especially since 2-3 year old ice that can be used as a resting/hunting platform for seals and polar bears in summer has not been declining since 2007.

Sea surface temperature

A graph of sea surface temperatures in August presented by authors Timmermans and Lab shows how cold it has been for the last two years in the Chukchi Sea (where Pacific walrus spend the summer), reflected the fact that sea ice in the region has not melted completely over the summer.

Primary productivity

The report by Frey and colleagues this year updates those from the last few reports and confirms that primary productivity–which means more food for seals, walrus, and polar bears–is still high in summer due to less sea ice coverage, especially in the Barents Sea, the Russian Arctic, the Bering/Chukchi Seas.

The authors conclude:

All regions continue to exhibit positive trends in primary productivity over the 2003-22 period, with the strongest trends in the Eurasian Arctic and Barents Sea.

Broad regions of lower-than-average primary productivity during 2022, particularly for the Beaufort Sea, East Siberian Sea, Greenland Sea, and Baffin Bay (associated with higher-than-average sea ice cover in these regions)…

In the graphic from the report below, note the slow overall increase in primary productivity in Hudson Bay and the Greenland Sea compared to other regions.

The report specifically mentions “higher-than-average sea ice cover” as the explanation for the Greenland Sea result but not for Hudson Bay (which is otherwise not mentioned in the report).

I wonder why?

The Beaufort Sea (data not shown) apparently also had lower than average productivity due to high sea ice cover.

These are the two regions mentioned most often as showing strong signs of declines in polar bear health and survival due to lack of summer sea ice, but I’m sure that’s just a coincidence.

Dying of sea birds

A report on 450 sea birds that died in the Bering and southern Chukchi Seas this year compared to previous years by Kaler and colleagues is a bit of a head-scratcher.

They admit they don’t really know why large numbers of birds have died in recent years but that often, the ultimate cause appears to be starvation.

They suggest this could be due to a decline in primary productivity caused by sea ice decline, in direct contradiction to the report by Frey and colleagues a few pages before:

Seabirds are sentinels of the status of marine ecosystems and these die-offs are concurrent with a massive ecological shift resulting from the loss of sea ice extent and duration in the Bering and Chukchi Seas.…

While the specific cause of why seabird die-offs have increased in frequency remains largely unknown, the decrease in sea ice extent and lipid-rich ice algae along with warmer ocean conditions are likely involved.

A short report by the US Fish & Wildlife Service on the phenomenon in 2016 noted that sea birds can starve to death if they haven’t eaten in four days, which makes them particularly vulnerable to any disruption of feeding, including by storms.

The graphic below, provided in the NOAA essay, shows that the huge die-off of common murres in 2015-2016 (event #7) overshadows all recent events. Only about 450 birds died this year, a relatively small amount compared to previous events.

Note that the common murre is perhaps on of the most common sea birds in the region and the Alaska population alone is estimated at 2.8 million birds in 230 colonies.

It is not unexpected, therefore, that many common murres die when conditions are challenging, whenever that happens (e.g. details in graphic below for 1970).

See more here polarbearscience.com

Bold emphasis added

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