Marine Heat Wave Research at GMRI
Note the lower panel and 30 year temperature trend line (gray) compared to the 9 year trend line (red). Also the yearly mean for 2012. GMRI Chart
The Gulf of Maine Research Institute (GMRI) has published a paper on the abrupt change in water temperatures seen in the Gulf of Maine in 2012. Kathy Mills a scientist at GMRI said the higher than average temperatures from Cape Hatteras to Iceland in 2012 demanded that scientists look at the scale – in both area and magnitude – and their effects on fisheries.
Temperatures were higher in 2012 but they had also developed three weeks ahead of schedule. This change effected inshore lobster migration, spawning and shedding. The timing of lobster landings was off as well which disrupted processors who were unable to handle the unexpected surge in product volumes.
Mills noted two objectives. First, while the 2012 temperature spike was one event it is very likely to be part of future weather patterns. Scientists work from models but they have not been studying how the effects of what their models tell them are impacting environmental systems and people. Second, addressing how management may have to adapt in order to be better prepared for future weather pattern impacts on fisheries.
Andrew Pershing and Janet Nye are scientists at GMRI and authors of papers on long range temperature changes in the Gulf of Maine (GOM).
There are two proposals in the pipeline looking at the water temperature problem said Pershing.
1. A project to look at the impact of warming events like 2012 and the general global warming trend on lobsters and the lobster fishery. This one is likely to start this fall, but until it’s official, it’s probably best to characterize it as something we hope to start.
2. A project to develop models to predict the timing of the peak lobster season and the composition of the catch (hard vs. soft shells) based on buoy temperatures. The idea is that these forecasts would be issued in the spring and updated as the season develops. Pershings initial stab at this is at: http://www.seascapemodeling.org/seascape_projects/2013/06/predicting-temperature-and-lobster-phenology.html
There is more information and graphs at Pershings website: seascapemodeling.org
Evidence of more southerly fish being found in the GOM is an indication of more sensitive fish on the move. When southern fish are seen in the GOM we know where they came from. A species of hake previously know to inhabit the continental shelf off New York is now in the GOM and Georges Bank.But when temperature sensitive historically native to the GOM fish disappear we don’t necessarily know where they specifically went to find cooler water.
Research Institutes at Boothbay Harbor and the Woods Hole Oceanographic Institute have ocean temperature records back 100 years. The records that scientists in the GOM use begin in 1981. That was when the first satellites were launched to record sea surface temperatures. It was in the late 1990’s that rising temperatures were seen to be impacting marine ecosystems.
Within the long-term trend of rising water temperatures there are decade long periods of more dramatic temperature changes both rising and falling. The water temperature event of 2012 is believed to be a part of a decadal period of change. Pershing noted that in the period from 1981 to 2012 sea surface temperatures rose .026 degrees C per year. Sea surface temperatures have risen .26 degrees C per year from 2004 - 2012. This translates to 0.05°F and 0.5°F. A 1/4 of a degree per year or a 10% rate of increase since 1981.
A similar figure to the one in the paper is in a blog post on potential impacts of warming on cod:
http://www.seascapemodeling.org/seascape_projects/2013/02/cod-in-the-gulf-of-maine.html
Pershing said it is very difficult to predict how temperatures will change. Predicting 5 days out or 20 years out is less difficult than making predictions for next year.
Temperatures on land that are 10 degrees above normal and last 3 to 5 days qualify as a heat wave. These temperatures can suddenly drop back to normal and things go back to normal. However, a one or two degree increase in sea temperature is a big deal. The higher temperature lingers longer. Water heats up and cools down more slowly than land.
The water temperatures in the GOM are affected by a more complicated natural system than the land areas. The normal seasonal melting of part of the ice cap sends cold fresh water into the GOM. That cold water flow has established stable patterns, currents, salinity changes, comfort and discomfort levels for marine life that rely on them.
How fisheries will be more broadly effected by sea water temperature changes and what kind of changes are needed on the management side to more effectively respond to these changes is what the GMRI proposals aim to study and draw conclusions.
Kathy Mills and Andrew Pershing have joint appointments with the University of Maine and the Gulf of Maine Research Institute.