A new study that improves upon pre-2005 ocean temperature estimates has found that the world’s oceans have been heating up thirteen percent faster than previously estimated, and that rate is increasing as time goes by. This new revelation is important, as the oceans absorb roughly 90 percent of the excess heat that the planet is retaining, making it not only an important indicator for how quickly the planet is actually heating up, but it also means that the danger posed by disproportionately warmer oceans is also greater than we feared.
Ocean temperatures are currently measured by the Argo float system, a network of approximately 4,000 submersible buoys spread around the world’s oceans, put into place in the early 2000s. However, before that, ocean temperatures were taken by sensors that were mainly deployed along major shipping routes in the northern hemisphere, with poor coverage in the southern oceans. This new study took the accumulated pre-Argo data and applied it to the more reliable (and extensive) Argo-gathered data, to extrapolate historical ocean temperatures back to 1960, and referenced it against the modern Argo data to test its accuracy.
What they found was that the world’s oceans have been heating up at a rate 13 percent faster than what was originally estimated, and that that figure is accelerating. Most of this heating has occurred since 1980, and beginning around 1990, that warmth has started to penetrate below the 700 meter (2,300 foot) mark. The oceans can absorb roughly 1,000 times the amount of heat that the atmosphere can before it starts to warm up itself, due to water’s unusually high specific heat capacity. But unlike the atmosphere, water doesn’t relinquish its heat energy back into space nearly as fast, meaning that whatever excess heat that global warming puts into the oceans will be around for much longer than we’d like.
While the temperature retained in the water itself might have been helping to buffer us land-lubbers from extreme atmospheric heating, there are still major consequences to a rapidly-warming hydrosphere: as water heats, it expands, causing an increase in ocean levels simply from the extra volume that the warmer water takes up — for instance, this is a major reason why storm swells along the US Atlantic and Caribbean coasts have been becoming more pronounced in recent years, due to an increased pooling of warm water there that would normally be crossing the Atlantic to northern Europe. Ocean-based storms themselves, such as hurricanes, also steadily increase in power, as there is more heat energy available in the water they form over to fuel the storm. Increased instances of algal blooms, faster ocean ice melt, and effects on aquatic wildlife are also dangers that can result from an increasingly warmer ocean.