For those of us living in California, one of life’s great tragedies is that the Pacific ocean is both so close to us, and so poor for actual swimming. Just to our west lies miles and miles of beautiful California coast and beaches, but spending more than five minutes in their waters sounds like a recipe for pain and thermal shock, rather than the leisurely fun that summer is supposed to bring.

So why are the California waters so cold, anyway? As always, the answer is a combination of several factors, all of which highlight the intricate complexity of our global ecosystem, and how the effects that we feel locally often originate from hundreds of miles away.

Perhaps the first, most obvious answer for California’s chilly waters lies in the ocean currents that carry water from up north. The dominant current that flows past California is part of the “North Pacific Gyre”, a giant spiraling circle of water that takes up most of the Pacific Ocean.