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Tumbling Down the Rabbit Hole Toward a Second Great Dying? World Ocean Shows Signs of Coming Extinction.
13
August, 2015
The
last time Earth experienced a Great Dying was during a
dangerous transition from glaciation and to hothouse.
We’re doing the same thing by burning fossil fuels today. And if we
are sensitive to the lessons of our geological past, we’ll put a
stop to it soon. Or
elsedoesn’t
even begin to characterize this necessary, moral choice.
*
* * * *
The
Great Dying of 252 million years ago began, as it does today, with a
great burning and release of ancient carbon. The Siberian flood
basalts erupted. Spilling lava over ancient coal beds, they dumped
carbon into the air at a rate of around 1-2 billion tons per year.
Greenhouse gasses built in the atmosphere and the world warmed.
Glacier melt and episodes of increasingly violent rainfall over the
single land mass — Pangaea — generated an ocean in which large
volumes of fresh water pooled at the top. Because fresh water is less
dense than salt water, it floats at the surface — creating a layer
that is resistant to mixing with water at other levels.
Algae
Blooms and Red Tides in the Stratified Ocean
This
stratified ocean state began to cut the life-giving thread of the
world’s great waters. Reduced mixing meant the great ocean currents
slowed. Oxygen transport into the depths declined. Moreover, a
constant rain of debris in the form of particulate matter from
burning forests and nitrogen oxides from the smoldering coal beds
fertilized the ocean surface. Food for algae also came from
increasing continental run-off. And
a spike in iron loading due to glacial melt added yet more
fertilizer.
Great microbial blooms covered the world ocean, painting its face
neon green, blue, or blood red.
(Stratified
Ocean waters hosting massive algae blooms. It’s a combination that
can quickly rob ocean waters of oxygen. During the Permian, a
transition to stratified and then Canfield Ocean conditions led to
the worst mass extinction event in the history of life on Earth.
Today, the Southern Ocean’s waters are increasingly stratified due
to glacial melt run-off of fresh water. In addition, these waters
also host very large algae blooms like the ones seen above in a NASA
satellite shot from 2012. Image source: NASA
and Live Science.)
Rising
CO2 levels increased ocean acidification even as the blooms spread
toxins through the waters. When the blooms finally exhausted all the
available food in their given region, they died off en masse. And by
decay they further robbed the waters of life-giving oxygen. At this
point the strains to ocean life became extreme and the first mass
deaths began to occur. The stress opened pathways for disease. And
the warming, de-oxygenating waters forced migrations to different
Latitudinal zones and ocean depths. What life there was that couldn’t
move, or couldn’t move fast enough died in place.
Transitioning
to a Canfield Ocean
At
first, ocean deaths appeared prominently in the bottom regions that
saw the most rapid declines in oxygen levels and the swiftest
increases in temperatures.
For not only did the fresh water at the surface of the world’s
oceans prevent mixing — it also prevented the oceans from
ventilating heat into the air. Instead, the ocean heat was
increasingly trapped at depth. Aiding this process of heat transport
into the world’s deeps was a bottom water formation that issued
from the hot Equator. There, evaporation at the surface increased
saltiness. The heavier, hotter, saltier waters sank — carrying with
them the Equatorial surface heat which they then delivered to the
ocean bottom.
The
hot, low oxygen bottom water became increasingly loaded with methane
as the heat activated frozen stores. It created an environment where
a nasty little set of primordial, hydrogen sulfide producing,
creatures could thrive.
These little microbes cannot live in oxygen rich environments. But
warm, anoxic bottom waters are more like the ancient environments
from which they emerged. Times long past when the world was ruled by
microbes in conditions that were simply deadly to the more complex
and cold-loving life forms of later times. To most life, the hydrogen
sulfide gas produced by these little monsters is a deadly toxin.
(Oxygen,
iron and hydrogen sulfide content of the world’s oceans over the
past 4 billion years. Ancient oceans were hotter than today. They
were rich in iron and densely populated with hydrogen sulfide
producing bacteria. They were also anoxic. During hothouse events,
oceans can again lapse into these ancient ocean states. Called
Canfield Ocean environments and named after Dr.
Donald Canfield who
discovered them, these states are extremely deadly to ocean life. If
they become too deeply entrenched, Canfield Oceans can also transform
the global atmosphere, resulting in extinctions of land animals as
well. Such an event was thought to be the primary killing mechanism
during the Permian Extinction. Image source: Nature.)
The
rotten-eggs stinking, hydrogen sulfide filled waters at first did
their dirty work in silence at the bottom of the warming world ocean.
But, steadily, anoxia progressed upward, providing pathways for the
hydrogen sulfide producing bacteria to fill up the oceans. Death
expanded from the bottom toward the surface.
In
all the great mass extinction events but,
possibly, one, this
heat-driven filling up of the world ocean with deadly hydrogen
sulfide gas during hothouse periods represents the major killing
mechanism. The other impacts of hothouse waters — ocean
acidification and habitat displacement — do provide killing
stresses. But the combined zero oxygen environment filled with a
deadly gas generates zones of near absolute death in which few things
but microbes and jellyfish can live. In rock strata, the anoxic,
zones are marked by regions of black as the hydrogen sulfide
producing bacteria-filled waters eventually take on the color of tar.
In the lesser extinctions, these black zones are confined to the
lower ocean levels. In the greater ones, they rise higher and higher.
During
the Great Dying, the oceans brimmed full of the stuff. Black, purple
and neon green waters bubbled to the surface to belch their lethal
loads of hydrogen sulfide gas into the airs. The gas was deadly toxic
to land plants and animals alike. And
it eventually wafted into the skies, turning it from blue to green
and eating away at the protective ozone layer.
In
this terrible way, more than 99 percent of all living things were
killed off. Of species,about
95 percent of ocean forms were lost with around 80 percent of the
land forms being wiped out.
Early
Signs of a New Ocean Extinction
The
Great Dying of the Permian Extinction 200 million years ago should be
a warning to anyone still enamored with the notion that today’s
terrifying fossil fuel burning results in any future that is not
horrible, wretched, bleak. Today, we dump 11 billion tons of carbon
into the air each year — at
least six times faster than during the Great Dying.
Today, the great melting glaciers are beginning the painful process
of ocean death by spreading out their films of stratifying,
iron-loaded fresh water. Today fossil fuel industry, industrial
farming and warming all together are fertilizing the ocean surface
with nitrous oxides, particulates, phosphates flushed down rivers,
and an overall increased runoff due
to a multiplication of extreme rainfall events.
(The
hot blob in the Pacific Ocean is setting off the largest red tide on
record. Just one of many dangerous impacts to sea life due to this
large region of abnormally warm water.)
And
the impacts are visible to anyone who cares to look. In the Pacific
Ocean, a
climate change related blob of hot water is resulting in mass ocean
creature die offs.
Low oxygen waters beneath the blob are wrecking large zones of ocean
productivity and risking the proliferation of deadly hydrogen sulfide
producing bacteria. The largest red tide on record has spun off the
hot blob. Covering
waters 40 miles wide and 600 feet deep, it has left piles and piles
of dead shellfish rotting on beaches across the North American West
Coast.
Across
the Continent, the Chesapeake Bay suffers a
proliferation of dead zones and greatly reduced productivity.
There’s a rising risk that, during coming years, increased warming
will deliver a heavy blow to life in the Bay and turn one of the
world’s greatest estuaries into a large hydrogen sulfide production
zone similar to the Baltic Sea. In the Gulf of Mexico, a similar dead
zone emerges near the outlet of the Mississippi. And out in the
Atlantic Ocean,mobile
dead zones now swirl providing
a roving surface hazard to both the deep open waters and to the
coastal regions that now sit in the firing line.
In
the Arctic, recently ice-freed waters are now the host of massive
blue and green Algae blooms.
(Large
blue and green algae bloom covering the southern Barents Sea during
late July of 2015. Large algae blooms are now a frequent feature of
previously ice covered waters in a warming Arctic. Image
source: LANCE-MODIS.)
Ever
since the mid 2000s a massive algae bloom like the one pictured above
has dominated the Barents Sea during summer time. Often running as
deep as 400 feet, this sprawling mat can rapidly deplete northern
waters of vitalizing oxygen and result in mass fish kills. Waters
around Greenland, in the East Siberian Sea, the Chukchi, and the
Beaufort have also hosted large, and potentially ocean-health
threatening algae blooms.
And,
in the polynyas and open waters off a melting Antarctica, massive
algae blooms are also starting to form.
Some of the blooms are so dense they emit a nasty rotten-eggs smell —
a sign that sulfide producing bacteria may already be active in some
of these waters. Fed by iron from melting glaciers, these immense
blooms represent rapid explosions of life that can equally rapidly
deplete waters of nutrients and then oxygen as they die off.
The
blooms and the related expanding, low oxygen dead zones now range the
entire world ocean. And where we see the red, the neon green, the
cloudy light blue what we see are the signs of another ocean
extinction in the making. An extinction that is likely building
faster than at any time in the geological past. But we may still be
able to avoid another great dying. The amount of carbon we’ve
emitted into the world’s airs is immense, but it is still but a
fraction of the carbon explosion that resulted in the Permian
die-off. It is still a tiny fraction of the carbon that remains in
the ground. The carbon that could be burned but shouldn’t. And a
rapid cessation of fossil fuel burning now should, hopefully, be
enough to prevent another hothouse spurred great dying in the oceans
and upon the lands.
As
for continued burning of fossil fuels — that results in
ever greater risk of unleashing the horrors of the ancient hothouse.
A set of now stirring monsters that we should carefully allow to fall
back into slumber — leaving them to rest in dreams of the great
long ago where they belong.
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