Another reason global warming has not been too bad yet is because the ocean absorbs most of the earth’s excess heat. But oceans are warming due to greenhouse gas emissions. According to the National Oceanic and Atmospheric Administration, half of the increase in ocean heat content since 1865 has occurred over the past two decades. Warmer water holds less oxygen, but the respiration rate of animals (except for marine mammals) increases with temperature, so they need more oxygen at the same time that less is available. A warmer ocean has less turnover (vertical water movements), which normally brings nutrient-rich water up from deep water to the plankton that photosynthesize near the surface. With fewer nutrients, they photosynthesize less and animals can’t get enough food.
Human actions have already increased carbon on the planet by about 40 percent. A quarter of that goes into the ocean. And the ocean has decreased by about .2 pH units, which may not sound like a lot. But, pH is a logarithmic scale like the Richter scale. So .2 pH is about 30% more acidic than it was before the Industrial Revolution.
In the vast and chaotic climate systems that govern our atmosphere and oceans, making sense of how one change — diminished sea ice — affects places or people thousands of miles away is a task of such extraordinary complexity that it strains even the most sophisticated supercomputers.
“Oregon is ground zero for ocean acidification impacts–the water chemistry off our coast is already changing and has changed dramatically. For a glimpse into the science, the impacts and the information gaps behind ocean acidification in Oregon, check out the… Read More ›
So the question is: Why have there been so many sightings outside late summer and early fall, the typical peak season for sharks?
The popular theory is that unseasonably warmer water has brought the change, but experts say it is much more complex than that.
Veteran diver Steve Lackey, an instructor at Sub-Surface Progression Dive Shop in Fort Bragg, said, “I try not to be an alarmist, but it is pretty unprecedented, in my opinion.”
This time of year, he’s accustomed to seeing small sprouts of kelp begin to appear on the ocean floor, a harbinger of the spring and summer growing season. This year, there are none, he said.
“I don’t remember quite this clean, this kind of scoured rock, with hungry invertebrates,” he said.
Though the tide can’t be totally turned back, the report, “Major Findings, Recommendations, and Actions,” found ways to blunt the environmental and economic impact now.
“Communities around the country are increasingly vulnerable to ocean acidification and long-term environmental changes,” said Richard Spinrad, chief scientist for the National Oceanic and Atmospheric Administration, and former OSU vice president for research. “It is crucial that we comprehend how ocean chemistry is changing in different places…”