The world’s oceans are changing. Dead zones, disappearing marine life, acidification, rising water levels and warming temperatures are all contributing to a crisis for marine ecosystems.
This summer saw the warmest ocean surface temperatures on record for July (62.5 F), surpassing the last record high in 1998, and combined average global land and ocean surface temperature that ranked fifth-warmest since global records began in 1880 according to data from the US National Oceanographic and Atmospheric Administration (NOAA).
NOAA data also showed the highest ocean surface temperature on record for June and the sixth warmest June on record for land temperatures.
For both months, ocean surface temperatures were 1.06 degrees F higher than the 20th century average. While this may seem like a small variation, it has a tremendous impact.
“Based on the physics of the oceans being such a vast reservoir for heat, small changes in ocean temperatures are massively significant for the amount of energy in the overall planetary climate system,” says Derek Arndt, Director of the Climate Monitoring Branch of NOAA’s National Climatic Data Center.
“As water warms, the concentration of absorbed gases it holds decreases.”
Evidence in Marine Life
Scientists are already seeing the repercussions of climate change in the bleaching of coral reefs, says Mark Eakin of NOAA’s Coral Reef Watch. When I spoke to him, he was on his way to Papua New Guinea for a joint project with Nature Conservancy to put instruments in place to measure water temperatures and coral bleaching with the hope of finding ways to protect reefs from the effects of climate change.
Coral bleaching was first seen on a large scale in the early 1980’s, during the 1982-83 El Niño cycle. During El Niño years, tropical storms that can cool the water are more rare, and the warmer water that characterizes the El Niño phenomenon can be devastating for corals, causing them to expel the symbiotic algae that gives them their color and that they rely on for nutrients.
Eakin does not believe that the current coral bleaching is simply an El Niño phenomenon, though.
“Since the 1980s, the frequency of bleaching events has been increasing and has been related to rising sea temperatures,” Eakin said.
In addition to the temporary warming trend of El Niño is the long-term trend of climate change. “Greenhouse gases are almost certainly the major driver of the warming planetary climate system and as part of that, ocean temperature surfaces will rise too,” Arndt said.
In Australia, official with the Great Barrier Reef Marine Park Authority are worried that continued warming from climate change will kill the massive reef in the coming decades. In a report this week, they suggest that the reef, home to some 1,500 species of fish, will be in serious trouble once atmospheric CO2 concentrations rise over 400 ppm. CO2 concentrations are already close to 390 ppm and rising.
“The overall outlook for the Great Barrier Reef is poor and catastrophic damage to the ecosystem may not be averted. Ultimately, if changes in the world’s climate become too severe, no management actions will be able to climate-proof the Great Barrier Reef ecosystem,” the authority writes.
NOAA warns that climate change and warming ocean temperatures also threaten other big changes in marine ecosystems, including the migration of fish species northward and disruptions in marine food chains. Higher temperatures also mean rising sea levels, threatening coastal ecosystems.
The Feedback Loops
NOAA’s recent arctic sea ice data is also cause for concern and a sign that dangerous feedback loops are starting.
Arctic sea ice covered an average of 3.4 million square miles during July — 12.7% below the 1979-2000 average extent and the third lowest July sea ice extent on record. The ice is vital to the climate because it reflects solar radiation, cooling the air and playing an important role in the ocean’s circulation.
According to a study released today by the National Center for Atmospheric Research, in the 1990s, Arctic temperatures reached their warmest level of any decade in at least 2,000 years. “If it hadn’t been for the increase in human-produced greenhouse gases, summer temperatures in the Arctic should have cooled gradually over the last century,” said NCAR scientist Bette Otto-Bliesner.
Methane releases from the ocean floor as the water warms pose another feedback problem. The UK’s National Oceanography Centre reports that a warming Arctic current, which has increased in temperature by about 1.8 degrees F over the last 30 years, has triggered the release of the global warming gas by breaking down the methane hydrate stored in the sediment beneath the seabed at depths below 400 meters.
“If this process becomes widespread along Arctic continental margins, tens of megatons of methane per year – equivalent to five to 10 percent of the total amount released globally by natural sources, could be released into the ocean,” warns Graham Westbrook, a geophysics professor at the University of Birmingham.
The team of scientists, which included researchers from the University of Birmingham, Royal Holloway London and IFM-Geomar in Germany, found that more than 250 plumes of bubbles of methane gas are rising from the seabed of the West Spitsbergen continental margin in the Arctic, in a depth range of 150 to 400 metres, something that has not been observed previously. This was not what the researchers were expecting to find.
“Our survey was designed to work out how much methane might be released by future ocean warming; we did not expect to discover such strong evidence that this process has already started,” said professor Tim Minshull, head of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre.
Scientists have known for over a year that the ocean’s surface warmed 50 percent faster during the last half century than previously thought. The latest information about ocean surface temperatures, arctic sea ice melt and warming arctic currents further demonstrates that the effects of climate change are upon us.
The oceans surface is a strong indicator of the speed and intensity of climate change, says Arndt.
“The ocean’s surface is the interface between the ocean component of the climate system and the other components of the climate system. It is more acutely sensitive to overall changes in the planetary climate and the first to experience wide scale changes, and it is also the most responsive.”
Oceans store more than 90 percent of the heat in the Earth’s climate system which make them a temporary buffer against the effects of climate change. If the warming surface temperature trend and warming arctic current continues, the oceans’ status as buffer may be coming to an end.
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(Photo: Great Barrier Reef/Landfelt/Flickr Commons)