Chapter 4 · Try it yourself

Warming Shift

The Gulf of Maine has been warming faster than almost any other patch of ocean. Fish and shellfish do not read maps; they follow the temperatures they like. Move through the years, then add a little future warming, and watch who wins and who loses.

1980
+0.0 °C

Added on top of the year you picked.

3. Show comfortable water for

Summer bottom water, 1980

Map of the Gulf of Maine and southern New England. MaineGulf of MaineGeorges BankSouthern New EnglandBostonBay of FundyCape CodLong Island 1980
°C: 5 · 10 · 15 · 20 · 25
  • Comfortable for lobster (5–18 °C)
  • Stressful for lobster (above 20 °C)

Simplified outlines. Illustrative summer bottom temperatures, not survey data.

Gulf of Maine surface anomaly, smoothed
−0.9 °C
compared with the 1991–2020 average

Share of the map with comfortable bottom water for each species, and change since 1980
SpeciesMap shareSince 1980

Gulf of Maine sea-surface temperature anomaly

Chart.

Simplified model. The curve is smoothed and illustrative, shaped to match published warming: Gulf of Maine surface waters warmed about 0.47 °C (0.84 °F) per decade from 1982 to 2025, nearly triple the global ocean average (Gulf of Maine Research Institute, GMRI, 2025 report); Pershing and others (2015, Science) found the Gulf warmed faster than 99% of the global ocean from 2004 to 2013 and linked that warming to the failure of Gulf of Maine cod to recover. Single years swing well above and below the curve; 2025 itself was the 15th warmest on record in GMRI’s series. Here every spot on the map warms by the same amount, and each species gets a rough comfort range for summer bottom water: lobster 5–18 °C (physiological stress starts above about 20 °C), cod 2–10 °C, northern shrimp below about 8 °C, black sea bass 12–25 °C. Real animals also respond to food, predators, currents, oxygen and fishing.