OCEAN CITY – Swimmers have been noticing an unusual chill in the water lately, with the ocean feeling colder than what is typically encountered during the height of summer.
With air temperatures soaring into the mid and upper 90’s this week, beachgoers look to the ocean to cool off, but many were met with a bit of a shock when they jumped into water that was colder than anticipated.
“We recorded water temps at 72 degrees, then all of the sudden it drops to 64 degrees again,” said Beach Patrol Captain Butch Arbin this week.
The local surf report showed water temps in the mid- to upper-60’s this week, down from temperatures in the mid- to low-70’s that swimmers were previously enjoying.
What’s the cause of the unseasonably chilly waters? According to Arbin, it could be a phenomenon known as upwelling, a wind-driven motion of the ocean’s waters that drives dense, cooler water toward the surface, replacing the warmer water that usually surrounds swimmers.
Arbin explained that water closer to the beach is typically warmer, as there is less water in the shallow regions of the shore break. Likewise, as you swim further out, the surface water is warmer than if you were to dive deep below the surface. That trend can change though depending on the wind.
Southerly winds often cause a circulation in the water that results in an “upwell” of colder waters that are beneath the warmer surface waters. As a result of the wind’s movements, surface water is pushed offshore. As the surface water moves offshore, the cooler water is drawn from below to replace it. The upward movement of this deep, colder water is called upwelling. The result; colder water temperatures.
“The top layer is blown to sea and the cold water comes up and replaces the top water,” said Arbin.
Conversely, a north or northeast wind brings warmer water temperatures. The north or northeast wind pushes the cold water back to the bottom, bringing the warmer water back to the surface.
Nor’easters could also bring warmer water temperatures. Nor’easters are storms featuring winds blowing from the northeast. The consistency of that northeast wind results in the warmer water temperatures.
“I don’t know if I would say this is a true upwelling,” said Arbin, noting a few years ago when the area experienced a more obvious case of upwelling, with temperatures suddenly dropping 20 degrees.
Although the recent temperature drop is less drastic, swimmers are still feeling the chill, said Arbin.
“An eight-degree measured drop over night, that’s a big change to how it feels to you.”