During the terrible mass extinction event at the Permian-Triassic boundary about 250 million years ago nearly all life on Earth was snuffed out. The event, which geologists have dubbed “The Great Dying,” occurred during a period of rapid warming on the tail end of a long period of glaciation (see A Deadly Climb From Glaciation to Hothouse: Why the Permian-Triassic Extinction is Pertinent to Human Warming). According to reports by Dr. Peter Ward, a prominent geologist specializing in causes of previous mass extinctions, the Permian extinction was composed of three smaller extinction events occurring over the course of about 50,000 to 80,000 years which together wiped out 96% of all marine species and 70% of all land species. Ward’s book “Under a Green Sky,” in my view, together with Hansen’s seminal “Storms of My Grandchildren” provide an excellent if terrible rough allegory of the climate beast we seem to be in the process of awakening.
(NCAR A2 model run shows global surface temperatures near those last seen during the PETM and Permian/Triassic extinction events by 2090 under a middle-range fossil fuel emissions scenario. A2 does include some added emissions via amplifying feedbacks from massive polar methane or CO2 stores along with other Earth Systems feedbacks. It is worth nothing that the P/T extinction occurred at the end of a glacial period while the PETM did not and was notably less pronounced. It also worth noting that global average temperatures are currently about .2 C above those seen in the 1990s.)
As noted above, Ward’s work focused on causes and what he found at numerous dig sites around the world was evidence of a ‘Great Dying’ that began at the ocean floor, proceeded upward from the depths, and eventually came to transcend the ocean boundary and inflict a similar, if less pronounced, lethality upon terrestrial organisms. The mechanism Ward proposed for the worst extinction in Earth’s geological memory involved how oceans and, in particular, living creatures in the oceans, respond to rapid warming. Ward found that during periods of high heat called hothouse states, oceans first became anoxic and stratified and then, during the worst events, transitioned to a deadly primordial state called a Canfield Ocean.
A stratified ocean is one in which the layers become inverted and do not mix. Warm water is avected toward the ocean bottom and a cooler layer on top keeps that warm layer in place. The warmer water beneath is oxygen poor and this results in more anaerobic microbes living in the deep ocean. Overall, global ocean warming also contributes to an anoxic state. Many of these microbes produce toxins that are deadly to oxygen dependent organisms. As they multiplied, the combined low oxygen/high toxicity environment created a layer of death that slowly rose up through the world ocean system.
The primary lethal agent Ward proposed for this action was hydrogen sulfide gas. This deadly gas, which has an effect similar to that of cyanide gas, is produced in prodigious quantities by an anaerobic bacteria whose remnants lurk in the world’s deep oceans. In lower quantities they turn the water pink or purple, in greater quantities — black. Oxygen is toxic to these primordial bacteria. And so, in the mixed oceans of the Holocene all the way back to the PETM boundary layer, these little monsters were kept in check by a relatively high oxygen content. But start to shut down ocean mixing, start to make the oceans more stratified and less oxygen rich and you begin to let these dragons of our past out of their ancient cages. And once they get on the move, these creatures of Earth’s deep history can do extreme and severe harm.
Ward hypothesized that these ancient organisms and the gas they produced eventually came to fill the oceans and then spill out into the atmosphere.
An anoxic, stratified ocean full of anaerobic organisms and out-gassing hydrogen sulfide to the atmosphere is a primordial sea state known as a Canfield Ocean. And Ward found that such hot, toxic waters were the lethal agent that most likely snuffed out nearly all life 250 million years ago.
A Climate Hockey Stick for the World Ocean System: Oceans Show Marked and Rapid Stratification Over the Past 150 Years
Peter Ward’s tone was nothing if not fearful in his book ‘Under a Green Sky.’ He wrote with the wisdom of a man who has come face to face with terrible limits time and time again. He wrote with the wisdom of a man shocked by some of the hardest truths of our world. He also made a plea — could scientists and experts of different fields please work together to give humanity a better measure of the risks he saw to be plainly visible.
Chief among these risks, according to Ward, included a rapidly warming planet. Ward found that both extreme high heat conditions as well as a relatively rapid pace of warming, in geological terms, increased the speed of transition to stratified ocean and Canfield Ocean states. Ward acknowledged that high rates of water runoff from continents likely contributed to anoxia. Recent studies have also indicated that rapid glacial melt combined with rapid global heating may contribute to a an increasingly stratified and anoxic ocean system.
Now, a new study of deep ocean corals entitled Increasing subtropical North Pacific Ocean nitrogen fixation since the Little Ice Age and conducted by researchers at the University of Santa Cruz and published in Nature has discovered proxy evidence that ocean stratification over the past 150 years advanced at the most rapid pace in at least the last 12,000 years. The study analyzed the sediment composition of coral growth layers to determine changes in ocean states since the 1850s. As the corals sucked up the dead bodies of micro-organisms over the past 1,000 years, the researchers were able to analyze what was happening to the cyanobacteria at the base of the food web.
What they found was that the bacteria increased their rate of nitrogen fixation by about 17 to 27 percent over the past 150 year period. And that this pace of change was ten times more rapid than that observed at the end of the Pliestocene and beginning of the Holocene 12,000 years ago.
(The Ocean’s Hockey Stick? Nitrogen Proxy Levels and Their Relationship to Climate Change.)
Increasing nitrogen fixation is an indicator of ocean stratification because cyanobacteria species under stress evolve to fix higher amounts of nitrogen from the surface transfer boundary with the air if particulate nitrogen levels in their environment drop. In a healthy, mixed ocean environment, nitrogen from various sources (terrestrial, run-off, etc), is readily traded between ocean layers due to the mixing action of ocean currents. In cooler oceans, more nitrogen is also held in suspension. But as oceans become warmer and more stratified, a loss of mixing and solubility results in lower nitrogen levels.
The researchers believe that this increase in nitrogen fixation is a clear indication that the region of the Pacific they observed is rapidly becoming more stratified and that this rate of increase is probably an order of magnitude faster than what occurred during the last major transition at the end of the last ice age.
“In comparison to other transitions in the paleoceanographic record, it’s gigantic,” Lead author Sherwood noted. “It’s comparable to the change observed at the transition between the Pleistocene and Holocene Epochs, except that it happens an order of magnitude faster.”
A separate study analyzing the nitrogen content of sea bird bones also provided proxy indication of a shift among cyanobacteria toward greater rates of nitrogen fixation, providing some additional confirmation for the increased ocean stratification observation. (An excellent article providing a more in depth exploration of these studies is available here.)
These studies combine with numerous observations of declining ocean health, increasing ocean hypoxia and anoxia, and an increasing number of observed mechanisms that may result in a more and more stratified ocean state as human warming intensifies to increase concern that the worst fears of Dr. Peter Ward and colleagues may be in the process of realization. (See: Dead Dolphins, Climate Change Devastating Ocean Fishermen, and Mass Starfish Die-off for more indicators of failing ocean health.)
Concerned Journalists and Terrified Ecologists
Put into various contexts, the current state of climate and environmental health does channel our worst fears that the Permian Extinction event may well be in for a human-caused repeat. The current estimated background extinction rate of 100-250 species per day is possibly the most rapid in all of geological history. The current CO2 level, near 400 parts per million, is higher than at any time during which human beings walked the Earth. The pace of greenhouse gas emissions is at least six times faster than at any time in the geological record. And the current, very large, forcing provided by humans does not yet include a probable powerful and unpredictable response from the Earth’s natural systems.
As Ecologist Guy McPherson notes — Nature Bats Last. And we should not be comforted by this notion. Because Nature carries the biggest stick of all. A consequence hanging over our heads that grows larger and more dangerous with each passing year during which our insults to her continue.
Among the pessimists regarding the end consequences of human caused climate change and related pollution, ecologists are the worst of the bunch. This is likely due to the fact that ecologists are very intimately involved in the study of how communities of organisms succeed or fail in natural settings. Among all groups of scientists, they are perhaps the ones most intimately familiar with the way in which all living things are connected to both one another and to the natural world. Ecologists know all too well that small shifts can mean huge changes to biodiversity, the rate of death among living beings, and the distribution of species in a given environment. But the changes humans inflict are not small in the least. They roughly ripple through the natural world in ways that ecologists know all too well have never before been seen.
Dr. McPherson is such an ecologist and one with such great conscience and concern that he, years ago, abandoned most of the luxuries of modern civilization to live in a fashion that produced the least harm possible. Not that this action has resulted in more optimism on his part. In fact, Guy is one of a growing group of people who believe that no action is likely to save humankind. That our insults to the natural world have already grown too great.
“We’ve never been here as a species and the implications are truly dire and profound for our species and the rest of the living planet.”
In this observation, Guy is probably right. But I sincerely hope that his and my own worst fears do not emerge.
It was Guy’s ongoing tracking of various dangerous alterations to world climate systems and assertion that human extinction may well be nigh that drew the attention of prominent journalist Dahr Jamail. Jamail recently penned the article: “The Great Dying Redux: Shocking Parallels Between Ancient Mass Extinction and Climate Change.“
Reading professor emeritus Guy McPherson’s blog was enough to convince Mr. Jamail of the risk that current warming could result in an extinction event to rival that of the Great Dying so long ago. Mr. Jamail notes:
It is possible that, on top of the vast quantities of carbon dioxide from fossil fuels that continue to enter the atmosphere in record amounts yearly, an increased release of methane could signal the beginning of the sort of process that led to the Great Dying. Some scientists fear that the situation is already so serious and so many self-reinforcing feedback loops are already in play that we are in the process of causing our own extinction. Worse yet, some are convinced that it could happen far more quickly than generally believed possible — even in the course of just the next few decades.
And so we come full circle. Rapid human warming leads to troubling ocean changes that hint at those feared to have resulted in mass extinctions during the Permian-Triassic boundary event. And the very rapid human warming puts at risk the catastrophically rapid release of Arctic methane which would certainly consign Earth to a rapid jump from a glacial to a hothouse state and potentially produce the kind of Canfield Oceans Dr. Ward fears. It is a deadly transition for which we have growing evidence with almost each passing day, one that McPherson and others fear could truly make an end to us and to so many other living creatures on this world.
So many scientists, so much valid reason to be dreadfully concerned, and yet we continue on the path toward a great burning never before seen in Earth’s history…
Links (Read them!):
Hat Tip to David Goldstein