The world’s oceans are turning acidic at what’s likely the fastest pace in 300 million years. Scientists tend to think this is a troubling development. But just how worried should we be, exactly?My dear Post reporter: It's a troubling development when your cat persistently coughs up fur balls on your bed when you're sleeping. It's a troubling development when your car starts vibrating every time it hits 60 mph. When the chemistry of the ocean is reverting towards a primordial condition when it emitted poisonous sulfurous gases, it is not a troubling development. It is the beginning of a fucking catastrophe of unimaginable proportions.
Here's a clue. Just because you don't know jack about the story you have been assigned don't assume there isn't a fossil record of mass death and destruction beyond anything ever witnessed by humans and beyond anything you are capable of imagining.
But it’s not fully clear what this all adds up to. What happens if the oceans keep acidifying and water temperatures keep rising as a result of global warming? Are those stresses going to wipe out coral reefs and fisheries around the globe, costing us trillions (as one paper suggested)? Or is there a chance that some ecosystems might remain surprisingly resilient?Yes, jellies (jellyfish) and invertebrates have survived multiple mass extinction events. As did sharks. So did cockroaches and scorpions. Three hundred million years ago, at the end of the Permian era, the earth's temperature soared and the oceans acidified when massive quantities of carbon were released as CO2 and methane after massive volcanic eruptions in Siberia.
The Permian ended with the most extensive extinction event recorded in paleontology: the Permian-Triassic extinction event. 90% to 95% of marine species became extinct, as well as 70% of all land organisms. It is also the only known mass extinction of insects. Recovery from the Permian-Triassic extinction event was protracted; on land, ecosystems took 30M years to recover.But a Post reporter can't tell the village that the oceans could acidify, stagnate and develop massive anoxic dead zones emitting sulfurous toxic gases. Ladies would faint.
There is also significant evidence that massive flood basalt eruptions from magma output lasting thousands of years in what is now the Siberian Traps contributed to environmental stress leading to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount of lava estimated to have been produced during this period, the worst-case scenario is an expulsion of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius.
Another hypothesis involves ocean venting of hydrogen sulfide gas. Portions of deep ocean will periodically lose all of their dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an anoxic zone, the gas can rise into the atmosphere. Oxidizing gases in the atmosphere would destroy the toxic gas, but the hydrogen sulfide would soon consume all of the atmospheric gas available to change it. Hydrogen sulfide levels would increase dramatically over a few hundred years. Modeling of such an event indicates that the gas would destroy ozone in the upper atmosphere allowing ultraviolet radiation to kill off species that had survived the toxic gas. Of course, there are species that can metabolize hydrogen sulfide.
Another hypothesis builds on the flood basalt eruption theory. Five degrees Celsius would not be enough increase in world temperatures to explain the death of 95% of life. But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines melted, expelling enough methane, among the most potent greenhouse gases, into the atmosphere to raise world temperatures an additional five degrees Celsius. The frozen methane hypothesis helps explain the increase in carbon-12 levels midway into the Permian-Triassic boundary layer. It also helps explain why the first phase of the layer's extinctions was land-based, the second was marine-based (and starting right after the increase in C-12 levels), and the third land-based again.
Let's play the old bait and switch. Let's talk about a nicer extinction event.
Another approach is to examine the fossil record. There have been multiple periods in the Earth’s history where atmospheric carbon dioxide levels rose sharply (for natural reasons) and the oceans became warmer and more acidic. That includes the Paleocene–Eocene Thermal Maximum, an era 55 million years ago with greenhouse-gas concentrations in the atmosphere roughly comparable to what the Earth could soon face.See, that's not so bad. Only large predators went extinct.
In a recent paper for Science, Norris and his co-authors found that this ancient world had few coral reefs, a poorly oxygenated ocean, and drastically different food chains that had difficulty sustaining large predators like sharks and whales. On the flip side, “the extinction of species was remarkably light, other than a mass extinction in the rapidly warming deep ocean.” So that’s one possible glimpse into our future: