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New Report: ‘Blowtorch’-Like Ocean Warming Advances Killer Seas, Shifts El Nino, Heats Hydrates

Tampering can be dangerous. Nature can be vengeful. We should have a great deal of respect for the planet on which we live. — Carl-Gustaf Rossby

But as the [IUCN] study points out, 90% of the extra heat that our greenhouse gases trap is actually absorbed by the oceans. That means that the upper few meters of the sea have been steadily warming more than a tenth of a degree celsius per decade, a figure that’s accelerating. When you think of the volume of water that represents, and then try to imagine the energy necessary to raise its temperature, you get an idea of the blowtorch that our civilization has become. — Bill McKibben

The scale of ocean warming is truly staggering with the numbers so large that it is difficult for most people to comprehend. — from the IUCN report Explaining Ocean Warming: Causes, scale, effects and consequences

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If there’s one simple fact about past Earth climates that should keep you awake at night, it’s this — warming the world ocean eventually produces a killing mechanism that is unrivaled by any other in Earth’s deep past. Great asteroids, gamma-ray bursters, earthquakes, tsunamis and volcanism — none of these can rival the vast damage to life on planet Earth that is resulting from ocean warming.

As a study of the sciences, this assertion would be merely an academic one if the human race weren’t now involved in a great injection of an unprecedented volume of greenhouse gasses into the Earth’s airs. As a critical new ocean report from the International Union for Conservation of Nature (IUCN) points out, these gasses are trapping an extraordinary amount of heat at the top of the world’s atmosphere. In turn, the atmosphere is transferring the lion’s share of this heat — more than 90 percent — into the waters of our world.

The Extreme Amount of Heat Energy Piling up in Our Warming Ocean

As a result, the surface of the world ocean is warming by 0.1 degree Celsius per decade. That may not sound like much, but it takes about four times the amount of energy to warm one gram of water by 0.1 C as it does one gram of air. This property, called specific heat, is a defining aspect of water. Water has the highest specific heat of any common substance.

heat-accumulation-human-forced-zillions-of-joules

(Since the 1970s, about 300 zettajoules’ (ZJ) worth of heat energy has accumulated in the Earth System due to fossil-fuel burning and related greenhouse gas emissions. That’s about 5 Hiroshima bombs worth of heat accumulating every second. Most of that energy has gone into the world’s oceans. So much heat is bound to have consequences, and these impacts are starting to show up in the form of declining ocean health, melting sea ice and glaciers, shifting climate zones and weather patterns, worsening droughts and storms, and threats of Earth System carbon feedbacks. Image source: Explaining Ocean Warming.)

Liquid water is also far denser than air. And this density generates an even higher impact heat energy transfer multiplier. So not only does it take four times more energy to warm a similar weight of water vs air, once warmed, that water contains that higher level of specific heat energy in a much more tightly concentrated package. And when that high heat concentration liquid water comes into contact with other substances — like ice in the form of ocean contact, or air in the form of evaporation, or frozen hydrates on the sea bed — it can pack a serious heat punch.

The vast volume of water in our oceans, therefore, serves as a kind of heat and energy regulator. It takes a lot of energy to warm it up, but once it does, serious environmental changes start to happen as a result. In other words, the temperature of the global ocean could be viewed as the point on which the whole of the Earth climate system pivots. Once the oceans are set in thermal motion, serious changes to the rest of the world are going to take place. To get an idea how much energy the oceans now contain, of how much potential they now have to dramatically alter our world, consider that if these vast waters were not present, the atmosphere now would have already warmed by 36 degrees C due to the heat-trapping effect of greenhouse gasses already in our atmosphere.

Fossil-fuel blowtorch indeed.

Heating Seas Ultimately Become Killer Seas

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.

barents-algae-bloom

(Massive algae bloom covers tens of thousands of square miles of open water in the Barents Sea during August of 2016. As glaciers melt, oceans stratify and warm; as water oxygen levels drop, and as hydrates vent due to warming, such blooms result in significant reductions to ocean health and a related global mass-extinction threat. Image source: LANCE MODIS.)

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.

El Niño Shifted, Ocean Hydrates Threatened

As alluded to earlier in this post, a new report, Explaining Ocean Warming, provides some pretty hard evidence that the oceans are on the move toward a much more harmful global climate state. The study, which has rightly received a great deal of media attention, issues a ‘shot across the bow’ warning to pretty much everyone living today. And it finds serious impacts to the ocean and linked climate systems due to a very rapid human-forced global warming.

These hard findings are worth reading directly:

  1. Sea-surface temperature, ocean heat content, sea-level rise, melting of glaciers and ice sheets, CO2 emissions and atmospheric concentrations are increasing at an accelerating rate with significant consequences for humanity and the marine species and ecosystems of the ocean.
  2. There is likely to be an increase in mean global ocean temperature of 1-4 degrees C by 2100. The greatest ocean warming overall is occurring in the Southern Hemisphere and is contributing to the subsurface melting of Antarctic ice shelves. Since the 1990s the atmosphere in the polar regions has been warming at about twice the average rate of global warming.
  3. There is likely to be Arctic warming and ice loss, and possibly the essential removal, in some years, of the summer Arctic sea ice within the next few decades.
  4. Over the last 20 years there has been an intensification and distinct change in the El Niño events, with a shift of the mean location of sea-surface temperature anomalies towards the central Pacific.
  5. Currently 2.5 Gt of frozen methane hydrate are stored in the sea floor at water depths of 200 to 2000 m. Increasing water temperature could release this source of carbon into the ocean and ultimately into the atmosphere.

These are all Earth-shattering scientific statements. For those who frequent this blog, points 1 through 3 are probably pretty familiar. The last two, however, require more in-depth explanation.

global-warming-el-nino

(Some scientific studies have pointed out that warming the world ocean will result in a shift of El Niño toward the central Pacific. A new ocean report finds that it’s already happening. Image source: Global Warming May Dent El Niño’s Protective Hurricane Shield, Increase Droughts.)

For a long time now, scientists have believed that El Niño wouldn’t be affected by climate change until the end of this century. But as with sea ice, it appears that such impacts may well be advancing faster than expected. As we’ve alluded to here, there’s been an apparent shift in El Niño toward the central Pacific over recent decades. This may well be a climate change-related shift. The fact that the IUCN report highlights this change is a sign that the broader sciences are starting to tackle the notion of early alterations to El Niño due to climate change as well.

However, the most ominous language here centers around methane hydrate. For years, there’s been adamant push-back against potential risks to hydrates coming from well-respected sections of the climate sciences. Nonetheless, those downplaying the threat of warming to hydrates have yet to produce any conclusive proof as to why warming the ocean bottom and applying heat to hydrates won’t result in at least some feedback from these carbon stores (especially under the higher-range warming scenarios). The IUCN report reiterates this risk by identifying 2.5 billion tons of frozen seabed methane at shallow and mid-ocean depths that will ultimately be exposed to warming — risking both an ocean and an atmospheric release.

These last points serve to underline some pretty basic facts, the chief of which is that pushing Nature, and heating up her life-blood world ocean waters, is a very, very dangerous game. And if this poignant new report sends any message at all it could simply boil down to this — turn back before it’s too late.

Links:

IUCN Report: Explaining Ocean Warming

Specific Heat

Ocean Warming

Awakening the Horrors of the Ancient Hothouse

LANCE MODIS

Slimy Green Algae Invades Florida

The oceans are heating up. That’s a big problem on a blue planet.

Global Warming May Dent El Niño’s Protective Hurricane Shield, Increase Droughts

Hat tip to Cate

Hat tip to George Hayduke

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Tumbling Down the Rabbit Hole Toward a Second Great Dying? World Ocean Shows Signs of Coming Extinction.

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 else doesn’t even begin to characterize this necessary, moral choice.

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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.

antarctic-algae-bloom-terra

(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.

Ancient ocean conditions

(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.

Barent Algae Bloom July 2015

(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.

Links:

A Deadly Climb From Glaciation to Hothouse: Why the Permian-Triassic Extinction is Relevant to Current Warming

Antarctic Glaciers are Loading the Southern Ocean Up With Iron (Not the Good News Some Are Making it Out to Be)

Large Algae Blooms off Antarctica

Under A Green Sky

Awakening the Horrors of the Ancient Hothouse

Canfield Oceans

Nature

K-T Extinction — Impact or Hothouse Caused?

Climate Change Happening Faster Than Scientists Predicted

How Global Warming Sets off Extreme Weather

Hot Pacific Ocean Runs Bloody

Pacific Algae Bloom is The Biggest Red Tide We’ve Ever Seen

Chesapeake Bay Dead Zones

The Atlantic Ocean’s Whirlpool Dead Zones

LANCE-MODIS

Triggers to Release the Methane Monster: Sea Ice Retreat, Ocean Warming and Anoxia, Fires, Sea Level Rise and The Fresh Water Wedge

Perhaps the most hotly debated topic among climate scientists, when they are not facing off with the ignorance of underhanded climate change deniers, is the potential rate of Earth Systems response to human caused climate change. In general, the low hanging fruit of climate research is a more easy to puzzle out pace of likely warming due to the direct forcing of human greenhouse gas and CO2 emissions and the more rapid climate feedback coming from increasing water vapor due to increased evaporation. But higher up the tree hang the critical fruits of pace of albedo change and pace of carbon response as the Earth System warms. Understanding these two will provide a much greater clarity to the question of a long term rate of warming given a doubling of atmospheric CO2.

Paleoclimate, Paleoclimate, and Paleoclimate

Perhaps the best way to test the accuracy of our long-term Earth Systems global warming and climate models is to use temperature proxy data from past ages in Earth’s history. And, based on these proxy measures, we find that the long term warming from each doubling of CO2 is at least 6 degrees Celsius. Though the proxies are not perfect, they are in general agreement on a range of potentials averaging near this figure. And these measurements can provide some confidence that the total long-term warming from a doubling of CO2 is at least twice that caused by a CO2 increase and the related water vapor rise alone.

More accurate measures closer to the current day are even less reassuring. Looking at the ice-age and interglacial transitions over the last 500,000 years, we find that a very small forcing provided by orbital changes, resulting in a global increase in solar insolation of about .5 Watts per meter squared combined with changes in the angle at which sunlight hits the Earth (Milankovitch Cycles), is enough to, over the long term, increase CO2 levels by 100 ppm (from 180 to about 280), increase methane levels by about 300 parts per billion (ppb) and (here’s the stunning kicker) raise world temperatures by a whopping 5 degrees Celsius globally and 13 degrees Celsius at the poles.

Changes in Temperature and Methane Concentration

Changes in Temperature and Methane Concentration

(Image source: NASA)

A Human Forcing Six Times Greater Than That Which Ended the Last Ice Age

It should be a serious concern to climate scientists that the initial forcing of just .5 Watts per meter squared resulted in a relatively moderate 100 ppm CO2 and 300 ppb methane response which then combined to force temperatures radically higher. By comparison, the current human emission of 120 ppm CO2 and 1100 ppb CH4 (methane) and rising, combine with other human greenhouse gasses such as Nitrous Oxide, Tropospheric Ozone (human emission), Clorofluorocarbons and Halons to provide an initial forcing of fully 3 Watts per meter squared or about 6 times the total forcing that resulted in the last ice age’s end and ultimately set in place feedbacks that pushed global temperatures 5 degrees hotter (Data source: Recent Greenhouse Gas Concentrations).

Earth’s Own Carbon Stocks are Vast

So why was so small an initial solar forcing enough to end an ice age and, ultimately warm the poles by 13 degrees (C) and the globe by 5 degrees C and what does this mean when the human forcing is now at least six times greater?

In short, the Earth holds vast stores of carbon in the form of CO2 in its oceans, organic carbon in its tundra and frozen beneath land ice, and in very large stores of methane hydrates on the sea bed. Any forcing that is large or occurs over a very long period of time will act continuously on these sources, pushing more and more of the carbon out until all of the stores newly exposed to that forcing are emitted, the feedback warming kicks in, Earth albedo changes as ice sheets respond (also a source of additional heat), and Earth gradually reaches a new energy equilibrium state.

In the current day, melting tundra (both land and ocean) in the Northern Hemisphere holds about 1,500 gigatons of carbon (NSIDC), the oceans contain between 2,000 and 14,000 gigatons of methane hydrate (USGS), and these same oceans hold about 1,000 gigatons of carbon (CO2) in solution near the surface and 38,000 gigatons of carbon near the sea floor (University of New Hampshire: Global Carbon Pools/Fluxes).

USGS Methane Hydrate

USGS Methane Hydrate

Melting tundra releases its carbon stores as CO2 in an aerobic/oxygen environment and as methane in an anaerobic and anoxic environment. Thawing methane hydrates release methane into the oceans of which some enters the atmosphere. And warming oceans eventually are unable to uptake a rising level of atmospheric CO2 and, in extreme cases, begin emitting CO2 back into the atmosphere.

When compared to the gentle, though long term, nudge to the Earth’s carbon stocks generated by orbital changes and a slight increase in solar insolation that ended the last ice age, the human forcing equates to a very great and rude shove. And if that much more gentle nudge was enough to liberate 100 ppm and 300 ppb of methane from the Earth system into the Earth’s atmosphere, then how much will the now much faster and harsher human forcing put at risk of liberation?

Methane Release Sources in the Arctic

That human greenhouse gas emissions are rapidly warming the Earth at a rate of about .2 degrees Celsius per decade and that carbon emissions from the Earth environment are likely to increasingly result from this rapid and rising rate of warming is a given. At issue is how fast and powerful an Earth systems response will be. And one critical issue in understanding the speed of this potential response is rate of methane release (CO2 release is another issue that will be explored in another blog).

Methane is a very powerful greenhouse gas. Over twenty years time, it estimated to produce about 105 times the forcing of a similar volume of CO2 (this value is estimated to be about 25 times a similar volume of CO2 over 100 years time). So large pulses of this gas could result in a doubling or more of the total greenhouse gas forcing already acting on the Earth system. Such catastrophic releases are hypothesized to have acted during other periods of rapid warming such as during the PETM and Permian hyperthermals.

The above, admittedly lengthy preamble, is needed to give context to this specific issue: potentially large methane releases as a result of Arctic warming and a number of related release mechanisms that may increasingly come into play. However, before we drill down to mechanisms, let’s look at the disposition of potential Arctic methane sources to give us a basis for our degree of concern.

Thawing Arctic Permafrost, as mentioned above, provides a source of 1,500 gigatons of carbon, some of which will be released as methane as it melts to liberate its carbon stores to surface, subterranean, and subsea environments. Some of this permafrost is land-based, some of it is submerged, as on the East Siberian Arctic shelf. As the permafrost thaws, decay and release of this carbon into the atmosphere is likely to gradually build, providing a growing pool of both methane and carbon emissions. That said, a climate change establishes a number of environmental mechanisms created that are likely to result in greater and greater volumes of this store being released over time. These mechanisms may push methane in a slow and gradual way. But, as we proceed down the dangerous path of rapid human-caused warming, there is increasing danger of large, sudden releases.

In addition, the same expanding set of environmental changes could result in a higher percentage of this vast store being emitted as methane.

Stable Sea Bed Clathrates represent an unknown portion that is likely a majority of the estimated 500-2,000 gigatons of methane hydrates in the Arctic environment. These clathrates compose methane locked in ice lattice structures that occur around 200 meters below the sea bed. Release of these clathrates requires a heat forcing to not only penetrate into the ocean waters, but for it to also reach the clathrates below hundreds of feet of rock and mud. Once the clathrates are disassociated, they must travel through cracks in the rocks and mud, and then through the water column to reach the ocean surface and the atmosphere. On the way, some of the liberated methane dissolves in sea water and another portion is taken in by methane eating organisms. If the pulse is strong enough, the ocean water saturated enough, and the methane eating organisms sparse enough, a greater portion of this released methane will reach the surface.

Ice Age Relics are clathrates that have formed as shallow as 20 meters beneath the sea floor. They are thought to have formed under the glacial cold that encased the Arctic over the last 2 million years and that occurred with particular intensity over the last 800,000 years. These ice age depositions are particularly vulnerable to more rapid release and their expansion during the last glacial period results in a set of carbon stocks that are very vulnerable to rapid emission. In this case, we find yet one more reason why a rapid rise out of a period of glaciation is a rather dangerous climate circumstance. The deposition of carbon stores are placed in regions more vulnerable to thaw and release once warming is underway.

In sum, these three represent a majority of potential methane release sources.

Rumors of Fire: The East Siberian Arctic Shelf Emission

(Please ignore the cheesy intro music and proceed on to the interview)

During the 1990s, researchers noticed a methane overburden in atmospheric regions around the Arctic Circle. This overburden was seen as an indication that large local methane emissions were occurring in the Arctic. Subsequent research found methane emissions from thawing Arctic tundra, from melt lakes and from peat bogs. In addition a large emission source was identified in the Arctic Ocean.

As of 2010, reports were coming in from the Arctic that the East Siberian Arctic Shelf was emitting more methane than the entire Earth ocean system combined. By 2011, an expedition to the Arctic found methane emission sources more than 1 kilometer across over the same region of submerged permafrost. By 2012, expeditions could no longer be conducted on the ice surface in the region of the East Siberian Arctic Shelf due to the fact that the sea ice there had become too thin and unstable to support research equipment.

Dr. Natalia Shakhova and Dr. Igor Similetov found that the permafrost cap over the shallow East Siberian Arctic Shelf seabed had become perforated. The cap locks a very large volume of methane, estimated to be about 500 gigatons, under constant cold and pressure. As the cap perforates, the cold and pressure release and increasing volumes of methane shoot up from the sea bed saturating the water with methane with some of the methane releasing to the surface.

Shakhova and Similetov warn that 1 percent or more of this methane could release over the course of decades as the sea ice continues to erode in the region of the East Siberian Arctic Shelf and the undersea permafrost continues to perforate. Just a 1 percent release would be enough to double the amount of methane in the Earth’s atmosphere, resulting in a .5 watt per meter squared forcing from an ESAS release alone. The researchers also identify the potential for a much larger, 50 gigaton release, which would more than double the current human GHG forcing over the course of just a few decades.

Such a large potential release was the subject of a much-debated Nature article by Peter Wadhams (read more here). And it was this article that raised the question of potential mechanisms that could result in such large releases of methane from the Arctic in the coming years.

The Arctic Under Heat: Ever More Powerful Mechanisms For Release

In examining potential release methane release mechanisms we will start with those currently acting on the East Siberian Arctic Shelf and work our way outward to the greater Arctic environment. It is worth noting that a paper by Carolyn Ruppel recently refuted Shakhova and Similetov’s findings, but that the Ruppel paper did not study the region of the East Siberian Arctic Shelf in question, only a related area of the Beaufort Sea which has not been found to currently show large, powerful, or widespread methane hydrate release.

East Siberian Sea

East Siberian Sea

(Image source: Commons)

Taking the Ice Lid off of a Shallow Sea. In the case of the East Siberian Arctic Shelf, rapidly warming air and ocean combine with rapidly retreating sea ice to create what seems to be a powerful and concerning release mechanism. The East Siberian Arctic Shelf is a 2 million square kilometer region that composes some of the Arctic’s densest carbon stores. It represents about 1/5 the Arctic Ocean area and is thought to contain about 500 gigatons of shallow sea bed methane hydrates. Over the past few decades, this region has warmed very rapidly, at the rate of about .5 degrees Celsius every ten years. This warming, at about 2.5 times the global rate, has resulted in a very rapid weakening and retreat of sea ice from the surface waters of a shallow sea that is, on average, about 50 meters deep. In recent years, summer sea ice has almost completely retreated from the ESAS, leaving a dark ocean surface to absorb sunlight and to rapidly warm. Measurements from the region show that water temperatures have increased by as much as 7 degrees Celsius above average once the sea ice pulls away. With the ice now gone, surface winds provide great mobility and mixing of the water column, this results in much of the surface water heating being transported down to the seabed. It also draws methane rich waters up from below where they can contact the air and release some of the water-stored methane.

Shakhova and Simeletov have observed perforations of the subsea permafrost releasing large volumes of methane from the East Siberian Arctic Shelf since 2008 and, as noted above, many of the hydrates stored beneath this permafrost cap are far shallower than is typical for a normal ocean seabed due to the fact that they are ice age relics. This combination of mechanisms provides the greatest current risk for rapid methane release. However, a number of other mechanisms are increasingly coming into play that may add to the, already concerning set of risks for rapid ESAS methane release.

Melting Tundra, Hot Lakes and Arctic Wildfires. NSIDC has identified about 1,500 gigatons of organic carbon locked in tundra systems throughout the Arctic. As the Arctic is forced to rapidly warm, larger and larger portions of this vast carbon store begin to thaw. Once the tundra melts, this carbon is subject to breakdown and action by microbes. This process of decay releases CO2 in dry environments and methane in wet, anoxic environments. Much of the tundra melt is subterranean. As such, this tundra melt is locked away in moist pockets that have little access to airflow. These pockets are at risk of being broken down into methane by anaerobic microbes. In some sections, tundra collapses and fills with water to form melt lakes. These lakes contact the anaerobic melt regions and create their own anaerobic bottom systems for carbon breakdown and release. Many of these lakes are so hot with methane that they provide emissions with high enough concentration to burn.

As the Arctic experiences more and more heatwaves, a far greater expanse of this extreme northern region is subject to wildfires. These fires are increasingly found to have burned deep into the soil. Reports from the Arctic find that fires have incinerated as many as 50% of the stumps of trees in a wildfire zone and consumed the carbon rich soil to a layer as deep as 3 feet below the surface. The action of wildfires further breaks open the soil and tundra cap providing passages to release any methane stored in anaerobic pockets beneath.

With these tundra regions composing so large a volume of carbon and with these areas being subject to increasingly rapid melting and increasingly energetic wildfires, larger and larger methane releases are entirely likely.

Ocean Warming, Anoxia, and the Fresh Water Wedge. As the years and decades progress and Arctic sea ice becomes more scarce, there is an increasing risk of large freshwater melt pulses from Greenland to combine with a warming Arctic Ocean to further amplify methane release. With the increasing removal of sea ice, Arctic Ocean temperatures surge, spreading a wider and wider area of heat forcing deeper and deeper into the water column and, eventually, into the seabed itself.

Some of this warming is visible in climate models projecting temperature and precipitation change throughout the Arctic over coming decades:

Projected temperature and precipitation change above the Arctic Circle.

Projected temperature and precipitation change above the Arctic Circle.

(Image source: Climate State)

A warmer Arctic Ocean is a less oxygen rich environment. The heat reduces the oxygen in solution, creating more anaerobic environments for organic carbon to break down as methane. Warmth also creates a greater sea-bed forcing for spontaneous and long-term release of methane hydrates.

As the seas surrounding Greenland warm and the Greenland environment takes in more of this latent heat, Greenland melt rates will continue to increase. The large fresh water pulses from Greenland will push the Gulf Stream further and further south, reducing the mixing of seawater in and near the Arctic, further reducing oxygen levels. These pulses will also act as a wedge, forcing warmer, saltier waters to dive down toward the ocean bottom as a fresh water cap expands from the Arctic Ocean southward (see Does Fresh Water Runoff Change Ocean Circulation to Unlock Deepwater Hydrates?). This mechanism will create a cool surface, hot depths ocean environment for the Arctic Ocean and northern latitude regions surrounding it.  Additional fresh water is likely to come from the continents as rates of precipitation increase, further adding to the fresh water cap and the creation of a growing region of stratified ocean with cooler, fresh water at the surface and a growing pool of warmer water below.

Unfortunately, large freshwater additions from melting snowcover and increasingly severe rainfall events, like the massive Yakutia floods have already resulted in changes to Arctic Ocean circulation, creating a large freshwater cap near the Beaufort and resulting in the risk of fresh water pulses entering the Pacific Ocean. A NASA animation shows how these changes are already ongoing:

And we have also noticed a great increase in ocean bottom heat content concentrated near the polar regions.

Thus we have three factors acting in concert to increase methane release. First, sea ice retreats to warm the Arctic Ocean. Second, increasing freshwater inflows divert the warmer waters toward the ocean bottom. Third, the warmer waters are less oxygen rich, creating more anoxic environments for anaerobic bacteria to break down organic carbon from thawing permafrost into methane. These anaerobes will receive plenty of nutrients from the waters washing off of glaciers and continents and will likely create great blooms over large areas as seas continue to warm. These combined forcing mechanisms will likely destabilize the weakest methane hydrate reserves first even as the anaerobes go to work on the newly liberated organic carbon.

Sea Level Rise Floods Large Regions of Tundra. A final mechanism for methane release is the rise of a less oxygenated Arctic Ocean to flood large sections of coastal tundra in Siberia, putting it under water and in an oxygen poor environment in which anaerobic bacteria can act to convert organic carbon into methane. A wide swath of coastal Siberia is low lying and, in some cases, is vulnerable to sea level rise for tens or even hundreds of kilometers inland. Over the years, larger sections of this region will be claimed by the sea, adding their carbon stores to an oxygen poor ocean bottom region.

Together, a rapidly destabilizing ESAS, a rapidly retreating ice sheet, increasing Arctic Ocean anoxia, increasing fresh water runoff into the Arctic Ocean, numerous anoxic environments within tundra thaw regions, increasingly energetic wildfires, expanding regions of stratified waters with hot ocean bottoms and cooler ocean surfaces, and seas rising to flood areas of thawing tundra provide sufficient and numerous mechanisms to be seriously concerned about Arctic methane release as an amplifier and potential multiplier to human caused warming.

Links:

Milankovitch Cycles

NASA: Changes in Methane Concentration

CDAIC: Recent Greenhouse Gas Concentrations

NSIDC: It’s All About Frozen Ground

USGS: Methane Hydrates

University of New Hampshire: Global Carbon Pools/Fluxes

Nature: The Vast Costs of Arctic Change

Does Fresh Water Runoff Change Ocean Circulation to Unlock Deepwater Hydrates?

A Looming Climate Shift: Will Ocean Heat Come Back to Haunt US?

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