Unraveling the Mystery: Warmer Sea with Cooler Summer

Rob Moir
2 min readJun 26, 2024

Why did sea surface temperatures go up when summer air temperatures did not? This perplexing question arose after last summer’s unusual findings.

Ocean surface water temperatures off Boston, Portsmouth, and Portland were nearly two degrees Fahrenheit warmer than usual, aligning with the long-term trend of increasingly warm conditions primarily driven by climate change.

To understand this, we must dive into the unique geography and ecosystem of the Gulf of Maine. This body of water is nestled between Nova Scotia to the North and Cape Cod to the South. Its connection to the Atlantic Ocean is only through a 60-mile-wide deep channel. This distinct geographical feature greatly influences the circulation and temperature of its waters.

The Gulf of Maine is nourished by several rivers, including the Neponset, Charles, Mystic, Merrimack, Piscataqua, Saco, Kennebec, Penobscot, and Saint John. These rivers flow into this 36,000-square-mile sea, making it less salty than the Atlantic Ocean.

Because of its lower density, freshwater from these rivers spreads across the sea’s surface during the summer, forming a distinct layer on top rather than mixing with the saltwater below.

River water input creates a counter-clockwise circulation due to the Coriolis Effect…

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Rob Moir
Rob Moir

Written by Rob Moir

Rob Moir is writing environmental nonfiction and writes for the Ocean River Institute and the Global Warming Solutions IE-PAC newsletter.