Water Temperatures in the Gulf of Maine This fall felt more like summer. a little too much.
Gulf of Maine Research Institute announced Inlet water heat, adjacent to Maine and northern Massachusetts, was among the highest on record between September and November – very high. Last year was about 0.5 degrees warmer than 2012, previously holding the title of hottest fall. During the season until the end of October, sea surface temperatures remained above 60 degrees Celsius, about 6 degrees above normal.
“this year [in the Gulf] Cathy Mills, who runs the Integrated Systems Ecology Lab at the Gulf of Maine Research Institute, said it was exceptionally hot considering how many days we were seeing heat wave conditions. “But I didn’t think about the aggregation of the impact that this year caused the hottest fall on record. . . . I was very surprised.”
The Gulf of Maine is warming faster than 96% of the world’s oceans – rising at a rate of 0.09 degrees per year over the past four decades. Over the past 10 years, many of the increases may be linked to ocean heat waves.
An oceanic heat wave is a period of five or more days where the sea surface temperature is in the 90th percentile higher than the average. The Gulf experienced oceanic heat wave conditions for most of 2021, with only brief breaks in late March, April and July. Heat wave conditions returned in August and persisted through the rest of the year. The largest declining temperature anomaly occurred on 16 October when the daily temperature reached 6.3 °C above the long-term average (1982–2011).
Heat waves in the region initially caught the attention of researchers in 2012, when warmer than normal temperatures prevailed over the region for almost the entire year. Since 2012, the warm season has only increased, especially in the later part of the year. Mills said summer and fall in the Gulf are warming almost twice as fast as winter and spring.
Since 2008, the decline in sea surface temperatures has warmed by about 1.1 degrees every decade. The average fall temperature has not dropped below 57 degrees Celsius since 2010. The four warmest fall seasons have occurred in the past seven years.
Nevertheless, a drop in sea surface temperatures was recorded in 2021.
Mills said last fall’s extraordinary heat may be triggered by a change in the broad ocean circulation pattern, which has been present in the region over the past decade.
He informed that this area is at present at a stage where Gulf Stream, a strong ocean current from the Gulf of Mexico that brings warm water into the Gulf of Maine, is moving north. Mills said Maine is “getting more of that hot water spinoff.” As the Gulf Stream moves north, it also interrupts the flow of the Labrador Current, which brings cooler water from the Labrador Sea into the Gulf of Maine.
“You’re turning the dial on warm water, you’re turning the dial on cold water, and that’s really contributing to the massive warming pattern that we’re seeing in the Gulf of Maine,” he said. said.
On top of this ocean circulation pattern, the Gulf’s exceptional warmth – the second warmest on record – also kept temperatures elevated throughout the fall season. Warmer-than-normal atmospheric conditions also prevented sea surface temperatures from cooling.
“Our fall temperatures are sustained over a long period of time, and it’s being affected by how hot we get during the summer,” Mills said. “If you’re starting from a high point in the summer and your temperatures are cooling down more slowly, it makes these fall temperatures look a lot different from earlier temperatures.”
The change in temperature in the waters of the Gulf did not go unnoticed. Over the past year, the Gulf of Maine Research Institute received reports of unusual animals in the area – including blue crabs, black sea bass and a smooth hammerhead shark. Other offshore marine species, such as river herring and striped bass, also stick around for longer periods of time rather than migrate.
The lobster industries have also adjusted to changes in temperature and ocean heat waves. Mills said the 2012 heat wave brought a significant amount of lobsters closer to shore than usual, causing much disruption to typical practices.
“The industry has really adjusted to that, and we don’t see those types of situations really causing the same alarm and problems that they did in 2012,” Mills said. She said some fishing boats are stocked with equipment to cool or oxygenate the water on stressful, high-temperature days, especially during the summer.
As species in the region change, Mills said, fisheries will need to adapt and plan. New species coming from the south may provide new opportunities.
“We can draw on the Gulf of Maine experiences to provide insights that will hopefully enable other ocean regions to prepare for change and to adapt to that change,” she said. “We’re on the front edge of that, with a lot of things happening very quickly here.”