Is water warmer off Atlantic or Pacific coast?

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Dear Tom,

I have taken boat trips off both the East and West coasts of the United States and it seems as if, on average, waters off the Atlantic coast are warmer than those off the Pacific coast. Is this true?

— Will Cantour

Dear Will,

You are correct. West Coast water temperatures are much lower than those along the East Coast. That is true because ocean waters rotate in clockwise fashion. This means Atlantic waters travel to the U.S. East Coast from the south and are relatively warm compared with West Coast Pacific waters that arrive from the north out of the chilly Gulf of Alaska. Looking at the entire oceans, however, the Pacific Ocean is by far the warmest overall ocean because it has about four times the intense sun-heated surface area in the tropics compared with the Atlantic Ocean.