Atlantic Ocean Currents Appear To Be Changing; So May Hurricane Season

Tropical Storm Alberto on May 18, 2018, in the Gulf of Mexico    Photo: NOAA/NASA

In a little-noticed report that could have major implications for both the Eastern U.S. and Europe, scientists announced last week that Atlantic Ocean currents are thought to be 15% weaker than in 1950The Washington Post explained, saying that the “system of currents that includes the Florida Current and the Gulf Stream, is now ‘in its weakest state in over a millennium,'” and this could make Europe colder in the winter and raise the rate of sea-level rise in the U.S. Atlantic seaboard. Similarly, a group of government scientists is looking at whether to change the official start of the Atlantic Hurricane season from June 1 to May 15 due to an increase in “early” tropical storms recently.

Why This Matters: We need to understand both these phenomena better to predict climate events.  They are quite a coincidence.  The warming of the Atlantic seems to be having profound and potentially permanent impacts on the Earth’s circulation system and on fisheries.  While the early storms may not be full-fledged hurricanes, they can cause damage–like  Tropical Storm Alberto in late May 2018, which caused nearly a foot of rainfall in central Florida.  And Friend of the Planet, Michael Mann, believes the slowdown in Atlantic currents is real even if the evidence is based on a mosaic of evidence.

The Current Slow Down

Scientists had long suspected the slowdown of the three major currents in the Atlantic, but it is hard to have definitive observations of these currents given that they have only had definitive measurements since 2004.  The new study published in Nature Geoscience found 11 sources of “proxy” evidence of the circulation’s strength, including clues hidden in seafloor mud as well as patterns of ocean temperatures. These currents are important because they transfer heat northward toward Europe and that moderates their climate. They redistribute heat worldwide, in fact, also bringing cool air and water to the south.  Parts of the Atlantic are getting markedly warmer — like the Gulf of Maine off the Northeastern U.S., which is warming faster than any other part of the Atlantic.  One of the most striking pieces of evidence, according to Michael Mann, is a recurrent “cold blob” that is not going away in the ocean to the south of Greenland —  and it is going against the overall global warming trend overall.

Longer Hurricane Season

The last six years have all had a named storm – though none were hurricanes – in May, and there have been 11 named storms in May since 2000. The National Hurricane Center told the Washington Post in an email, “Many of the May systems are short-lived, hybrid (subtropical) systems that are now being identified because of better monitoring and policy changes that now name subtropical storms.”  In fact, the average first storm of the season is now more than a month earlier than it was in 1970, but some of that change may be attributable to better storm detection thanks to modern weather satellites.  The hurricane season start date is really just a formality — it helps to get the public focused on storm preparation.  And it’s only about a hundred days away now.  Forecasters fear that this season could once again be active like last year, given the observed La Niña weather pattern and a number of other atmospheric factors.

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