Nova Scotia·Weather

2021 was the warmest year on record in the Gulf of Maine

2021 was one of the warmest years on record across the Maritimes and northeast United States. One big contributing factor for record temperatures in places like Yarmouth, N.S., was offshore in the Gulf of Maine, where sea surface temperatures were also the warmest on record.

Sea surface temperatures in the Gulf of Maine were more than two degrees above average

In this Sept. 13, 2017, file photo, a lobster fishing boat heads out to sea at sunrise off shore from Portland, Maine. (The Associated Press)

Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled Our Changing Planet to show and explain the effects of climate change and what is being done about it.


2021 was one of the warmest years on record across the Maritimes and northeast United States.

While many locations in the region finished in the Top 5, the temperature recorded in Yarmouth, N.S., was the warmest on record, topping both 1999 and 2012. Records date back to 1879. 

One big contributing factor for Yarmouth's record temperatures was offshore in the Gulf of Maine, where sea surface temperatures were also the warmest on record.

Scientists at the Gulf of Maine Research Institute say that temperatures in the gulf averaged 12.3 C in 2021, which is more than two degrees above the average and tops the previous record set back in 2012.

Bar plots of absolute sea surface temperature (SST) values (top panel) and SST anomalies (bottom panel) for the top five warmest years in the Gulf of Maine. (Gulf of Maine Research Institute )

2021 was truly a remarkable year in the Gulf of Maine.

An annual time series of daily average sea surface temperatures shows that the gulf reached "marine heatwave" criteria for 360 of the 365 days last year.

A marine heatwave is defined as a period when there are five or more consecutive days when the observed sea surface temperature is greater than 90th percentile of the average for that day.

This timeseries illustrates that in 2021 the Gulf of Maine experienced marine heatwave conditions for almost the entire year. The grey dashed line is the annual cycle of the long-term average sea surface temperature for 1982-2011. The red dotted line is the marine heatwave threshold. (Gulf of Maine Research Institute)

Gulf of Maine Research Institute research was the first to sound the alarm back in 2014 that the Gulf of Maine is warming faster than the vast majority of the oceans in the world, and not surprisingly that trend continues.

The rate of warming continues to be high not only in the Gulf of Maine, but along the entire Atlantic coastline of Nova Scotia.

The Gulf of Maine, left, and the world’s oceans, right, warmed from 1982 through 2021. Yellow areas indicate regions that are warming faster than 97.5 per cent of the world’s oceans. (Credit: Gulf of Maine Research Institute)

Historically, the cooler Labrador current moving southward has kept the warmer waters of the Gulf Stream out to sea. However, the study points out that with climate change, more melted sea ice and fresh water is constricting the flow of the Labrador current and allowing the warmer water from Gulf Stream to "spill over" into the Gulf of Maine.

The research also points to the North Atlantic Oscillation, or NAO, which is a large-scale pattern that varies in our atmosphere. The study says it's been a positive phase more frequently over the past 10-15 years, which is resulting in less Arctic air masses moving into the region.

A heat map of daily sea surface temperature anomalies from the beginning of 1982 through the end of 2021. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade. (Gulf of Maine Research Institute )

The scientists say this rate of change in the gulf and our surrounding ocean temperatures can have profound consequences for the biology of ocean species and entire food chains.

The continued warming of our surrounding ocean waters is having an impact on our temperatures back here on land as well. Those warmer bodies of water release latent heat into the atmosphere, even when air temperatures drop at night and in the fall and winter seasons.

The list of the top 10 warmest years on record in the Maritimes is now almost exclusively filled with years since 1999.

ABOUT THE AUTHOR

Ryan Snoddon

Weather

Ryan Snoddon is CBC's meteorologist in Nova Scotia and New Brunswick.

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