Temperature surge likely to have dramatic impacts on aquatic life
There may be more trouble ahead for New England-based fishermen, as a new NOAA study shows that ocean temperatures along the U.S. Northeast Shelf are projected to warm twice as fast as previously projected and almost three times faster than the global average. The findings are based on a complex analysis of several different climate models.
“We looked at four GFDL models and compared their output to ocean observations in the region,” said said Vincent Saba, a NOAA fisheries scientist and lead author of the study.”Prior climate change projections for the region may be far too conservative,” Saba said in NOAA press release.During the past ten years, the Gulf of Maine has warmed faster than 99 percent of the global ocean, likely due to a northerly shift of the Gulf Stream. That already led to a shift in the distribution and composition of species, and additional warming as much as 5.4 to 7.2 degrees Fahrenheit will likely cause more extreme effects on the ecosystem.
The study appears in the Journal of Geophysical Research – Oceans, published by the American Geophysical Union.
The global climate models assessed by the Intergovernmental Panel on Climate Change are coarse resolution models based on a roughly 100-kilometer or 62-mile grid. The new projections are based on a more fine-scale look.
“It is like comparing an old standard definition television screen to today’s ultra high definition screens,” said Saba, a member of the Northeast Fisheries Science Center’s Ecosystem Assessment Program who works at GFDL. “There aren’t many high resolution global climate models available due to their prohibitive cost. For much of the global ocean the coarser resolution is okay, but when you are studying a unique location like the Gulf of Maine, with its complex bathymetry of deep basins, channels, and shallow banks combined with its location near the intersection of two major ocean current systems, the output from the coarser models can be misleading.”
The study also found that the warming of the upper 300 meters (roughly 1,000 feet) of the Northwest Atlantic increases salinity due to a change in water mass distribution related to a retreat of the colder, fresher Labrador Current and a northerly shift of the warmer, saltier Gulf Stream.
Observations and the high-resolution climate model show a strong relationship between a weakening Atlantic Meridional Overturning Circulation and an increase in the proportion of warm-temperate slope water entering the U.S. Northeast Continental Shelf, primarily through the Gulf of Maine’s Northeast Channel.
“These results show the need to improve simulations of basin and regional-scale ocean circulation,” said Saba, who will use the CM2.6 model findings for a variety of climate studies on living marine resources in the ecosystem.
In addition to Saba and Jonathan Hare from NOAA Fisheries’ Northeast Fisheries Science Center, other study authors are affiliated with NOAA’s Geophysical Fluid Dynamics Laboratory and the Earth System Research Laboratory in Boulder, Colorado.