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"Long before it's in the papers"
April 10, 2015

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Persistent “warm blob” in Pacific linked to strange weather

April 10, 2015
Courtesy of the University of Washington
and World Science staff

Strange weath­er has struck the Un­ited States in re­cent months—and some sci­en­tists say they have an ex­plana­t­ion, in ad­di­tion to the glob­al warm­ing gen­er­ally ac­knowl­edged to be oc­cur­ring.

A per­sist­ent patch of warm wa­ter off the West Coast, about 1 to 4 de­grees Cel­si­us (2 to 7 de­grees Fahr­en­heit) above nor­mal, is con­tri­but­ing to the may­hem, ac­cord­ing to two pa­pers to ap­pear in the jour­nal Geo­phys­i­cal Re­search Let­ters

The West Coast has been warm and parched; the East Coast has been cold and snowed un­der. Fish are swim­ming in­to new wa­ters, and hun­gry seals are wash­ing up on Cal­i­for­nia beaches. 

The warm patch “was­n’t caused by glob­al warm­ing, but it’s pro­duc­ing con­di­tions that we think are go­ing to be more com­mon with glob­al warm­ing,” said Nick Bond, a cli­mate sci­ent­ist at the Uni­vers­ity of Wash­ing­ton who in­ves­t­i­gated the “blob” and coined the term. The ef­fects on weath­er in the ar­ea are sim­i­lar, he added, and it’s “a taste of what the ocean will be like in fu­ture dec­ades.” 

He went on: “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.”

Bond said the huge patch—1,000 miles (1,600 km) wide and 300 feet (100 meters) deep­—had con­tri­but­ed to Wash­ing­ton’s mild 2014 win­ter and might sig­nal a warm­er sum­mer. Ten months lat­er, the blob is still there, now squished up against the U.S. coast and ex­tend­ing about 1,000 miles off­shore from Mex­i­co up through Alas­ka, Bond said. He added that all the mod­els point to it con­tin­u­ing through the end of this year. 

His study con­cludes that the blob is re­lat­ed to a per­sist­ent “high-pres­sure ridge,” or an elon­gat­ed ar­ea of high at­mos­pher­ic pres­sure, that caused a calmer ocean dur­ing the past two win­ters. As a re­sult the ocean lost less heat. It thus was due to less win­ter cool­ing and not more heat­ing, said Bond.

Bond and his co-authors, in­clud­ing U.S. Na­t­ional Oce­an­ic and At­mos­pher­ic Ad­min­istra­t­ion sci­en­tists, looked at how the blob is af­fect­ing West Coast ma­rine life. They not­ed fish sight­ings in un­usu­al places, sup­port­ing re­cent re­ports that West Coast ma­rine ecosys­tems are suf­fer­ing and that warm, less nutrient-rich Pa­cif­ic Ocean wa­ter is dis­rupt­ing the food web. 

The blob’s in­flu­ence al­so ex­tends in­land, they argue. As air passes over warm­er wa­ter and reaches the coast it br­ings more heat, which the pa­per said helped cause cur­rent drought con­di­tions in Cal­i­for­nia, Or­e­gon and Wash­ing­ton. The blob is just one el­e­ment of a broader pat­tern in the Pa­cif­ic Ocean whose in­flu­ence reaches much fur­ther, they added—pos­sibly to in­clude two bone-chilling win­ters in the East­ern U.S.

A study in the same jour­nal by Den­nis Hart­mann, an at­mos­pher­ic sci­ent­ist at the uni­vers­ity, looks at the Pa­cif­ic Ocean’s rela­t­ion­ship to the cold 2013-14 win­ter in the cen­tral and east­ern Un­ited States. De­spite much talk of a “po­lar vor­tex,” Hart­mann said we need to look south to un­der­stand why so much cold air shot down in­to Chi­ca­go and Bos­ton. His study points to a dec­ades-long pat­tern in the trop­i­cal Pa­cif­ic linked with changes in the North Pa­cif­ic, called the North Pa­cif­ic mode, that sent at­mos­pher­ic waves snak­ing along the globe to br­ing warm and dry air to the West Coast and very cold, wet air to the cen­tral and east­ern states. 

In a blog post last month, Hart­mann fo­cused on the more re­cent win­ter of 2014-15 and ar­gues that again, the root cause was sur­face tem­per­a­tures in the trop­i­cal Pa­cif­ic. That pat­tern, which al­so causes the blob, seems to have be­come stronger since about 1980 and lately has el­bowed out the Pa­cif­ic Dec­a­dal Os­cilla­t­ion to be­come sec­ond only to El Niño in its in­flu­ence on glob­al weath­er pat­terns, he went on.

“It’s an in­ter­est­ing ques­tion if that’s just nat­u­ral vari­abil­ity hap­pen­ing or if there’s some­thing chang­ing,” Hart­mann said. “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.”


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Strange weather has struck the United States in recent months—and some scientists say they have an explanation, in addition to the global warming generally acknowledged to be occurring. A persistent patch of warm water off the West Coast, about 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above normal, is contributing to the mayhem, according to two papers to appear in the journal Geophysical Research Letters. The West Coast has been warm and parched; the East Coast has been cold and snowed under. Fish are swimming into new waters, and hungry seals are washing up on California beaches. The warm patch “wasn’t caused by global warming, but it’s producing conditions that we think are going to be more common with global warming,” said Nick Bond, a climate scientist at the University of Washington who investigated the “blob” and coined the term. The effects on weather in the area are similar, he added, and it’s “a taste of what the ocean will be like in future decades.” He went on: “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.” Bond said the huge patch —1,000 miles in each direction and 300 feet deep—had contributed to Washington’s mild 2014 winter and might signal a warmer summer. Ten months later, the blob is still there, now squished up against the U.S. coast and extending about 1,000 miles offshore from Mexico up through Alaska, Bond said. He added that all the models point to it continuing through the end of this year. His study concludes that the blob is related to a persistent “high-pressure ridge,” or an elongated area of high atmospheric pressure, that caused a calmer ocean during the past two winters. As a result the ocean lost less heat. It thus was due to less winter cooling and not more heating, said Bond. Bond and his co-authors, including U.S. National Oceanic and Atmospheric Administration scientists, looked at how the blob is affecting West Coast marine life. They noted fish sightings in unusual places, supporting recent reports that West Coast marine ecosystems are suffering and that warm, less nutrient-rich Pacific Ocean water is disrupting the food web. The blob’s influence also extends inland, they say. As air passes over warmer water and reaches the coast it brings more heat, which the paper said helped cause current drought conditions in California, Oregon and Washington. The blob is just one element of a broader pattern in the Pacific Ocean whose influence reaches much further, they added—possibly to include two bone-chilling winters in the Eastern U.S. A study in the same journal by Dennis Hartmann, an atmospheric scientist at the university, looks at the Pacific Ocean’s relationship to the cold 2013-14 winter in the central and eastern United States. Despite much talk of a “polar vortex,” Hartmann said need to look south to understand why so much cold air shot down into Chicago and Boston. His study points to a decades-long pattern in the tropical Pacific linked with changes in the North Pacific, called the North Pacific mode, that sent atmospheric waves snaking along the globe to bring warm and dry air to the West Coast and very cold, wet air to the central and eastern states. “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,” Hartmann said. In a blog post last month, Hartmann focused on the more recent winter of 2014-15 and argues that again, the root cause was surface temperatures in the tropical Pacific. That pattern, which also causes the blob, seems to have become stronger since about 1980 and lately has elbowed out the Pacific Decadal Oscillation to become second only to El Niño in its influence on global weather patterns, he went on. “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.”