Giant blob in Pacific Ocean is responsible for odd weather in the US

Unusually warm temperatures dominate three areas of the North Pacific: the Bering Sea, Gulf of Alaska and an area off Southern California. The darker the red, the further above average the sea surface temperature. Photo credit: NOAA

Unusually warm temperatures dominate three areas of the North Pacific: the Bering Sea, Gulf of Alaska and an area off Southern California. The darker the red, the further above average the sea surface temperature. Photo credit: NOAA

Two studies, published earlier this year in the journal Geophysical Research Letters, have unveiled that a mysterious ‘warm blob’ of water in the Pacific Ocean is probably responsible for the recent weather weirdness in the US.

The mysterious blob, off the West Coast of the US, was initially discovered in June 2014 and since then it has extended by around 1,000 miles offshore, from Mexico to Alaska. It now covers an area that is 2,000 miles across and 300 feet deep.

In the latest study, offshore sea surface temperatures (SST) in the NE Pacific were found to be abnormally warm during the winter of 2013-2014. The patch of water was one to four degrees Celsius warmer than surrounding regions of water. Temperatures recorded were the greatest observed in this region for this particular time of year since at least the 1980s.

Scientists believe the SST anomalies, that exceeded 2°C during winter 2013-2014, were not formed by global warming, but were rather caused by an anomalous weather pattern since the sea level pressure (SLP) was unusually high in this particular region. Using a mixed layer temperature budget, the scientists discovered that the high SLP reduced the loss of heat from the ocean to the atmosphere and lead to anomalous horizontal advection in the upper ocean. This was responsible for the weak seasonal cooling in the four month period before the maximum SST anomaly. In other words, the warmer temperatures within the blob are not due to more heating, but rather less winter cooling.

The anomalous horizontal advection is partly due to anomalous Ekman currents. Weaker than usual winds from the west resulted in anomalously weak Ekman currents transporting colder water from the north. Basically, the cold air that normally absorbs the heat from the ocean was diverted.

In a separate study, a shift in the Pacific Decadal Oscillation (PDO) from a negative to a positive, warm phase has been suggested as the cause of the blob. PDO is a pattern of Pacific climate variability which is remarkably similar to ENSO, but on a much larger scale. The PDO can remain in the same phase for 20-30 years compared to ENSO cycles typically lasting 6-18 months.

Regardless of the cause, the blob is having biological impacts. It was found that its presence coincided with unusual biological events and species sightings. For example, sunfish and a thresher shark were spotted off the South East coast of Alaska during summertime surveys, which is abnormal as they are usually found in more temperate or even tropical waters.

Not only is the blob having an effect on marine life, but as the air passes over warmer water and reaches the coast it brings with it more heat and therefore less snow, which explains the current drought in California, Oregon and also Washington. The expansion of the blob is also believed to be the main cause of the thousands of starving sea lion pups stranding along the California coastline since the beginning of the year.

Scientists say the drought could be a dress rehearsal for what climate change could soon bring.

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Lucy Grable

Lucy Grable

MSc Species Identification and Survey Skills student at Reading Uni | BSc Marine Zoology | Website Editor MARINElife | Zanzibar humpback whale researcher|Marine wildlife enthusiast

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