Why has the US West Coast been unusually warm and dry, while the East Coast has experienced abnormally cold and snowy conditions? It’s partly down to “the blob”, says Nick Bond, a climate scientist at University of Washington-based Joint Institute for the Study of the Atmosphere and Ocean.
The ‘blob’ could also be why fish are swimming into new waters and hungry seals are ending up on California’s beaches.
The ‘blob’ is a term dubbed by Mr. Bond in his monthly newsletter for a long-lived patch of warm water off the West Coast of the US, about 2°F to 7°F (1°C to 4°C) above normal. He writes about this phenomenon in the journal Geophysical Research Letters (citation below).
The warm blob earlier this week, now squished up against the West Coast. The scale bar is in degrees Celsius. (Credit: NOAA National Climate Data Center)
“In the fall of 2013 and early 2014 we started to notice a big, almost circular mass of water that just didn’t cool off as much as it usually did, so by spring of 2014 it was warmer than we had ever seen it for that time of year.”
Dr. Bond said the massive patch of water is about 1,000 miles (1,600 kilometers) across and 300 feet (91 meters) deep. He believes it has been a major contributory factor to Washington’s mild 2014 winter and a likely warmer-than-usual 2015 summer.
Now, the ‘blob’ is about 1,000 miles offshore and spans from the north of Mexico right up to Alaska. Its temperature is about 3.6°F (2°C) higher than it should be. According to all his models, the patch is likely to be there right through to the end of 2015.
Where does the ‘blob’ come from?
In a new study, Dr. Bond and colleagues are trying to find out where the blob comes from. They believe it is linked to a persistent high-pressure ridge that brought about a calmer ocean during the last two winters, so less heat dissipated to the cold air above.
The current warmer temperatures have not been caused by more heating, but less winter cooling.
The researchers report fish sightings in unusual places, backing recent reports that West Coast marine ecosystems are suffering and the food web is being disrupted by warm, less nutrient-rich Pacific Ocean water.
The blob is also affecting inland weather. As air passes over warmer-than-normal water and hits the coast, it brings more heat and less snow, which the study shows contributed to the parched conditions in Washington, Oregon and California.
According to the American Geophysical Union, the blob is one of several elements, apparently, of a broader pattern in the Pacific Ocean which is affecting the climate of the United States right across to the East Coast, which has had two severely cold winters.
Pacific Ocean’s link to cold winters on central and eastern US
In a separate study, also published in Geophysical Research Letters (citation below), Professor Dennis Hartmann, who works in the Department of Atmospheric Sciences at the University of Washington, looks at the Pacific Ocean’s relationship to the cold winter in the central and eastern United States in 2013-14.
Prof. Hartmann says we should look south to understand why Boston and Chicago got so much cold air.
His study shows that a decadal-scale pattern in the tropical Pacific Ocean associated with changes in the North Pacific, called the North Pacific mode, sent atmospheric waves snaking along the globe to bring very cold, wet air to the central and eastern US states and warm and dry air to the West Coast.
Prof. Hartmann said:
“Lately this mode seems to have emerged as second to the El Niño Southern Oscillation in terms of driving the long-term variability, especially over North America,.”
That pattern, which he says also causes the blob, appears to have gained strength since about 1980, and lately has become second only to El Niño in its impact on global weather patterns.
Prof. Hartmann said:
“It’s an interesting question if that’s just natural variability happening or if there’s something changing about how the Pacific Ocean decadal variability behaves,” Hartmann said. “I don’t think we know the answer. Maybe it will go away quickly and we won’t talk about it anymore, but if it persists for a third year, then we’ll know something really unusual is going on.”
While the blob does not appear to be caused by climate change, Dr. Bond explains that it has many of the same effects for West Coast weather. “This is a taste of what the ocean will be like in future decades. It wasn’t caused by global warming, but it’s producing conditions that we think are going to be more common with global warming,” he said.
“Causes and Impacts of the 2014 Warm Anomaly in the NE Pacific,” Nicholas A. Bond1, Meghan F. Cronin, Howard Freeland and Nathan Mantua. Geophysical Research Letters. DOI: 10.1002/2015GL063306.
“Pacific sea surface temperature and the winter of 2014,” Dennis L. Hartmann. Geophysical Research Letters. DOI: 10.1002/2015GL063083.