Posts
Through
The Looking Glass of The Great Dying: New Study Finds Ocean
Stratification Proceeded Rapidly Over Past 150 Years
18
December, 2013
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.
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.
McPherson
notes:
“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.”
Guy
is probably right. 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
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