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Unusually cold water has appeared along the United State’s Atlantic coast this summer, chilling swimmers and bringing fish that don’t usually appear until the onset of fall. Thermometers in the surf near Nags Head, North Carolina, show a temperature of 60 degrees Farenheit—it’s typically close to 80 at the end of July. There are a handful of theories to explain the strange conditions: winds are blowing warm surface waters out to sea, forcing cold water from the ocean depths to upwell along the coast; a current is carrying cold water from the north; increased stream runoff from the summer’s high rainfall is cooling the ocean surface; or the absence of warm-water eddies which normally spin off from the Gulf Stream. NOAA scientists are currently studying data from satellites and ocean buoys, hoping to find an explanation, while many beachgoers sunbathe instead of swimming.
On land, the passage of a severe storm might be marked by fallen trees or swollen streams. In the ocean, a hurricane leaves a swath of cold water in its path. That trail of cold water marks the passage of Hurricane Bertha through the North Atlantic Ocean in this sea surface temperature image.
La Niña, the large area of cold water in the Pacific Ocean widely blamed for last summer's drought and often related to an increase in the number of hurricanes that make landfall, appears to be on its last legs.