The NAO seafood oscillation

Figure 1A, Changes in Jet Streams due to Negative and Positive North Atlantic Oscillation

(Source: http://www.climatewatch.noaa.gov/wp-content/uploads/2010/03/NAO_Schematic.png)

ScientificAmerican Headline: Warming Oceans Means Seafood Menu Changes

Guest post by Bob Tisdale

ScientificAmerican recently published a post on their ClimateWire titled Warming Oceans Means Seafood Menu Changes. The article should actually be titled A Well Known North Sea Climate Shift Linked Years Ago to the North Atlantic Oscillation Changes Seafood Menus. The ScientificAmerican post is a cross post the E&E News article FOOD SECURITY: As oceans warm and become more acidic, Britain’s seafood menu changes. It begins:

LONDON — The seas around Britain are starting to teem with fish species once deemed exotic as climate change raises water temperatures, forcing the former dominant occupants to flee northward toward the Arctic and opening the way for those from the hotter south, according to marine and fisheries scientists.

Such is the extent of the migration already observed, which is expected to grow in coming decades and could even force a change in the country’s fish menus. Once-local species are moving farther afield and therefore becoming more expensive to catch, while formerly foreign ones become plentiful locally and therefore presumably cheaper and easier to harvest.

“People have started calling the North Sea the crucible of climate change. It has warmed by about a degree Celsius over the last 50 to 100 years, which is something like six times faster than pretty much any marine area around the world,” John Pinnegar, program director of the Marine Climate Change Centre at the government’s Centre for Environment, Fisheries and Aquaculture Science, told ClimateWire.

The “crucible of climate change”? There must be lots going on in the relatively small North Sea. The article includes the seemingly mandatory reference to climate change:

“The British have very traditional fish eating habits — historically consuming predominantly cod in the south and haddock in the north. Not many people are used to eating red mullet and sea bass. But eating habits can change, and that is partly what adapting to climate change could mean,” he added.

AccuWeather picked it up, too. Tom Nelson titled his cross post Hmm: Other than the North Sea, “pretty much any marine area around the world” has only warmed about 1/6 of one degree C. in the last 50-100 years? And JunkScience published those opening three paragraphs (see here) with a lead-in that reads:

Wow! Think of the savings on vinegar if the seas actually were becoming acidic! They aren’t though and while the fillets may change with varying ocean currents the UK’s ubiquitous fish & chips will still be fish and chips.

I, of course, was interested in the claim the North Sea had “warmed by about a degree Celsius over the last 50 to 100 years, which is something like six times faster than pretty much any marine area around the world.”

First I went to the GISS mapmaking webpage. I used their trend analysis option for sea surface temperature data (excluded the land surface data) to see if I could confirm the claim that over the past 50 to 100 years the North Sea warmed at a rate that was six times faster than elsewhere around the global oceans. Figure 1B shows sea surface temperature anomaly trends from 1962 to 2011 (50 years). The trends in numerous places around the globe were about the same as those in the North Sea. I’ve circled the North Sea for those wondering where it is. And Figure 2 shows the 100-year trends (1912-2011). There are parts of the global oceans that have higher linear trends over the past century. Well, so much for the North Sea being “the crucible of climate change”. Oddly, Googling “the crucible of climate change” and “North Sea” in quotes provided only 46 results, with most referring to the E&E article. Others had nothing to do with the North Sea. If people have “started calling the North Sea the crucible of climate change”, they’ve been pretty secretive about it.

Figure 1B

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Figure 2

Let’s take a look at the Reynolds OI.v2 sea surface temperature data. It’s a satellite-based dataset and has been available for a little more than 30 years. We’ll use the coordinates of 51N-61N, 3W-10E for the North Sea. See the map in Figure 3, which was created to show the region captured by the coordinates and to show the sea surface temperature anomalies for the week centered on June 27, 2012. Doesn’t look too warm there last week.

Figure 3

And a time series graph of North Sea data reveals a relatively high, but not astronomically high, linear trend since November 1981. It’s NOT “something like six times faster than pretty much any marine area around the world”. And the North Sea temperature data appears to have peaked already and might be on its way down.

Figure 4

Maybe the long-term data reveals something unusual. The North Sea sea surface temperature anomalies (HADISST) from January 1870 to April 2012 are shown in Figure 5. I’ve also shown the data with a 13-month running-average filter to smooth out some of the variations. Although there’s lots of variability (noise), the sea surface temperatures there are remarkably flat for the first 110+ years. Then it appears to make a quick rise starting about 1987. Figure 6 compares the linear trends before and after 1986/87.

Figure 5

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Figure 6

Not too surprisingly, the shift in the North Sea sea surface temperatures about 1987 has been the study of numerous papers. And guess what? The majority have primarily been about regime shifts in fish. One of the first papers I found on the subject was Alheit et al (2005) Synchronous ecological regime shifts in the central Baltic and the North Sea in the late 1980s. The abstract begins:

The index of the North Atlantic Oscillation, the dominant mode of climatic variability in the North Atlantic region, changed in the late 1980s (1987–1989) from a negative to a positive phase. This led to regime shifts in the ecology of the North Sea (NS) and the central Baltic Sea (CBS), which involved all trophic levels in the pelagial of these two neighbouring continental shelf seas. Increasing air and sea surface temperatures, which affected critical physical and biological processes, were the main direct and indirect driving forces.

Under the heading of North Sea, Alheit et al (2005) write:

An ecological regime shift occurred in the North Sea ecosystem in the late 1980s that affected all trophic levels including phytoplankton, zooplankton, and benthos to fish (Reid and Edwards, 2001). It has been linked to a shift to a positive NAO index that coincided with an increased incursion of warm oceanic water from the Atlantic into the northern North Sea (Edwards et al., 2001; Reid et al., 2001a; Beaugrand, 2003).

Hmm. Let’s see. So far we’ve seen that the North Sea sea surface temperatures have increased, but the trends are not “six times faster than pretty much any marine area around the world.” We’ve seen that the recent warming has actually been tied to a shift in sea level pressure represented by the North Atlantic Oscillation, and the impacts of the naturally caused warming on sea life have also been studied for years. That raises a very basic question: why is this news?

And now for something completely different. The E&E news article also includes the following paragraph that dampens the climate change reference:

“Sea temperatures are rising — although it is hard to say whether this is a blip in geological terms or evidence of global warming. But with it we would expect to see some changes in the species distribution of fish,” said Richard Handy, director of the Ecotoxicology Research and Innovation Centre at Plymouth University’s School of Biomedical and Biological Sciences.

But then the E&E article returns to the Pinnegar interview with his discussion of climate model projections:

“The model predictions suggest that Iceland and Greenland — Greenland in particular — and Norway are probably going to benefit in terms of fisheries from climate change, at least for the next 50 to 100 years,” Pinnegar said.

Now, we’ve all seen how much skill climate models have shown at hindcasting sea surface temperatures since 1900 and at hindcasting and projecting sea surface temperatures over the satellite era (the last 30 years). A one word summary: None. Refer to the discussions of Figures 15 through 20 in the post Part 2 – Do Observations and Climate Models Confirm Or Contradict The Hypothesis of Anthropogenic Global Warming? and the two-part post Satellite-Era Sea Surface Temperature Versus IPCC Hindcast/Projections Part 1 and Part 2. Or if you prefer, those discussions are also included in my first book If the IPCC was Selling Manmade Global Warming as a Product, Would the FTC Stop their deceptive Ads?

Why some people have confidence in climate models is beyond me.

SOURCES

The Reynolds OI.v2 sea surface temperature data is available through the NOAA NOMADS website. It’s also available through the KNMI Climate Explorer, as is the longer-term HADISST data.

HAT TIP

Many thanks to Joe D’Aleo of IceCap and WeatherBell for the heads-up on the article.