Area of warming
An unusual threat is looming off the Pacific coast of North America from Juneau in Alaska to Baja California. Now roughly 2000 kilometres wide and 100 metres deep, a mass of warm water that scientists are calling 鈥渢he blob鈥� has lingered off the coast for a year and a half and has set temperature records, with waters between 1聽掳C and 4聽掳C warmer than normal.
Fresh research published in Geophysical Research Letters has examined the causes and impacts of this area of water, which has grown more recently.
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The blob has changed water-circulation patterns, affected inland weather and reshuffled ecosystems at sea. Although scientists say the planet鈥檚 warming oceans may not be responsible for the mysterious and long-lived anomaly, some see it as an early warning of changes that might be coming to the Pacific in the next few decades.
Satellite imagery first alerted scientists to the strange formation in August 2013, when the roundish blob was seen over the Gulf of Alaska. Researchers think that a long-lasting weather pattern called a high-pressure 鈥渞idge鈥� deflected winds that stir up cool waters from the deep and bring cool air and water from high latitudes.
Unusually warm sea-surface temperatures are being observed in the North Pacific. The darker the red colouring, the more above average the temperature (Image: NOAA)
Months later, fishermen and officials around Alaska reported sightings of species found in more temperate or even tropical waters, including skipjack tuna, thresher sharks and sunfish. Other marine species showed up thousands of kilometres north of their normal ranges, including pygmy killer whales and tropical species of copepods 鈥� tiny crustaceans that are key to marine food webs.
鈥淚鈥檝e never seen some of these species here before,鈥� says plankton expert of the Northwest Fisheries Science Center in Seattle, Washington 鈥� part of the National Oceanic and Atmospheric Administration.
Spreading warmth
The anomaly has spread out over the last 12 months, with warm water showing up all the way from Alaska to the central Mexican coast. Physical oceanographers have speculated that the blob is influenced by a major climate pattern known as the Pacific Decadal Oscillation (PDO), a combination of several phenomena that have the effect of warming water across the eastern Pacific for periods of 4 to 20 years.
Yet the patterns of warming seem to be different this time round, says oceanographer of Scripps Institution of Oceanography in San Diego, California. 鈥淭his is a phenomenon beyond the typical PDO-like oscillations we鈥檝e seen for the recent decades,鈥� he adds. 鈥淚鈥檓 in a state of confusion.鈥�
Inland, the blob contributed to a number of unusual weather events along the Pacific Northwest last summer, including an uptick in thunderstorms and lightning 鈥� and the resulting forest fires.
But the biggest impacts so far have concerned marine species. Peterson fears that a big drop in copepod populations in waters off the Pacific Northwest could doom harvests of various species of salmon 鈥� a multibillion-dollar industry 鈥� for years to come. 鈥淭hey had nothing to eat,鈥� he says of juveniles that ventured out from rivers into the blob last year.
Thousands of seabirds called Cassin鈥檚 auklets have been found dead along the Pacific shore, and conservationists have had to rescue scores of starving sea lions on beaches in southern California.
Journal reference: Geophysical Research Letters, DOI:
