“There’s a starker message to convey here, one that focuses on this simple yet dire question — how do warming oceans kill? In basic terms, they become toxic and anoxic. Warming oceans melt ocean-contacting glaciers. The glacial melt forces seas to rise and forms a freshwater lid on the global ocean, breaking down ocean conveyor belts and preventing mixing. This freshwater lid also deflects heat toward the ocean bottom. This process in turn helps to thaw methane hydrates. Warm waters that don’t mix and that are filled with bubbling hydrates become very oxygen-poor.“
As the land glaciers bleed out into the oceans, the stratified, oxygen-deprived waters become less and less able to support advanced life. The kinds of life warm, oxygen-deprived waters do support are poison-producing microbes. These microbes thrive in the warm, oxygen-poor waters. If ocean heating continues to progress, the warming seas will eventually fill up with their deadly byproducts. Among the most nasty of these is hydrogen sulfide. If enough of it is produced, it will spill out from the ocean into the nearby air, resulting in land animal mortality as well.“
In microcosm, we saw a mild taste of some of these effects this past year in Florida as toxic algae blooms filled the warming state’s waterways and coastlines, even forcing some riverside marinas to close due to toxic gasses wafting up from the purple-green, oxygen-starved waters. These effects are a snapshot of a possible future for Earth’s oceans if we don’t get our act together yesterday.” –Robert Scribbler.