The Gulf of Maine’s basins and banks create eddies that retain and warm its waters.
Photo: Jack Cook, Woods Hole Oceanographic Institution
How Climate Change Affects York County’s Beaches
By Kevin McKeon, Maine Master Naturalist
Current national political forces seem to be discouraging our friendly Canadian neighbors from visiting our nearby ocean beaches. However, many of us continue to welcome our northern friends to our clean, white sands and cool waters, which are heavily influenced by the Gulf Stream Current. So maybe we could take a quick peek into this heat-controlled phenomenon.
Our devoted school science teachers have shown us that heat really doesn’t like itself, always seeking a cooler area — like the stove burner’s heat moving to the fry pan, and from the pan to your eggs, and from all three to the kitchen’s air. So now envision rays from the sun (stove burner) heating sea water (fry pan), then forming a layer of warm sea water (eggs), and those three refracting and reflecting warming rays into the atmosphere (kitchen air). This heat movement, along with Earth’s rotation, helps to generate both the eastern trade winds and the Atlantic meridional overturning circulation (AMOC) — the Atlantic Ocean’s air and water currents.
Part of the AMOC is the Gulf Stream, at about 5.6 mph Earth’s fastest ocean current, flowing northeasterly along our Atlantic coast from Florida to mix with cold Labrador waters. Because Labrador’s cold water is heavier than the warm Gulf water, it sinks, causing a rush of Gulf water to replace it, energizing the Gulf Stream. The sinking cooled water forms a deep-water channel flowing south, under the Gulf Stream, along the eastern North and South American coasts, then separating at the Antarctic coast into the Indian and Pacific oceans. Other ocean currents are similarly formed, energizing Earth’s Ocean currents, called the Global Ocean Conveyer Belt. As the global currents meander, they exchange heat with the atmosphere, modulating Earth’s temperature.
Our teachers have also shown us that air absorbs heat faster than water — so as global warming increases, the atmosphere heats faster than oceans. The atmosphere, trying to release heat, gives it to the cooler ocean, warming it. This forms a deeper, wider, and warmer stratified surface water layer. Also, since warm air holds more water than cooler air, this water-laden atmosphere fuels an increase in storm severity. These warm rains get further warmed by Earth’s surface, adding more heat to Maine’s (and Earth’s) river waters flowing to the ocean.
Polar ice is frozen fresh water, which is less dense than seawater, so as increasing volumes melt, it resists sinking. Combined with warming sea water, the descent of the Labrador Current to the depths is slowed — thus slowing the Gulf Stream. The slowed current allows the equatorial Eastern trade winds, which blow from the east to the west, to push the warming and thickening Gulf Stream Current closer to the Eastern Seaboard — and the Gulf of Maine — where the shallow coastal waters remain warmer due to the thickening warm, stratified layer. Geologically, the Gulf of Maine is a huge bathtub, comprised of deep basins enclosed by shallow underwater sea banks. The increasingly warming Gulf Stream and Labrador currents flow into our bathtub and are restrained, held within various eddies, resulting in an especially egregious warming of Maine’s Gulf. And as we’ve seen, this warming water expands, adding to sea level rise, further increasing the severities of coastal storms.
Our warming Gulf has other sinister effects. Nutrients that normally get mixed and carried in turbulent ocean currents supply food for the ocean’s plankton and other lower tropic levels. As the warm, stratified layer grows, nutrient mixing between water layers decreases, causing nutrients to sink to the depths and decay — which depletes oxygen and sea life. Also, ocean waters are absorbing increasing levels of carbon from the atmosphere, activating chemical reactions resulting in ocean acidification, which retards plankton growth. Why is plankton important? It’s the source not only of the ocean’s food chain, but also of over half of the oxygen we breathe!
Watch this video produced by a NASA, MIT, and UT Austin Echo Model project, explaining the Global Ocean Conveyer Belt. Science has demonstrated that carbon-releasing fossil-fuel burning since mid-1800 from the surging Industrial Revolution has slowed the AMOC by 15-20%, the slowest in 1,600 years. A complete stop is becoming increasingly probable, as has happened several times between 71,000 and 12,000 years ago. Scientists are continually seeking and analyzing global warming data to better inform us of likely impacts caused by a slowing of Earth’s great stabilizing force — The AMOC — and our own Gulf Stream Current.
Notice in the diagram how the Gulf of Maine’s waters form a huge eddy between Cape Cod and Nova Scotia, sitting atop the shallow continental shelf. This relatively thin eddy holds and slows heat transfer to the cold return current. Maine’s coastline is warming due to these many factors, all related to heat transfers between air, soil, and water. So as oceans warm, the Gulf of Maine is warming three times faster than just about any other place on Earth and staying warmer longer — to the delight of many beachgoers from here and to some of our Canadian friends, but not good news for our coast.
Ocean current video: https://www.youtube.com/watch?v=R5-s6O8qyvE
Editor’s note: Did you see something unusual last time you were out in the woods? Were you puzzled or surprised by something you saw? Ask our “Out in the Woods” columnist Kevin McKeon. He’ll be happy to investigate and try to answer your questions. Email him directly at: kpm@metrocast.net
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