I would like to acknowledge a debt of gratitude to Guy McPherson, Paul Beckwith, Sam Carana, Robertscribbler, and others in helping me to write this.
This refers to a phenomenon that is likely to be regional (affecting Britain most of all) and temporary. In the end Heat will trump.
This refers to a phenomenon that is likely to be regional (affecting Britain most of all) and temporary. In the end Heat will trump.
An 'Ice Age' coming?
The
weakening Gulf Stream
Seemorerocks
Yesterday the above picture was posted, of Atlantic ocean currents. It elicited the following comment from nuclear scientist Prof Chris Busby.
“Gulf
stream seems to failing. i have noticed increasingly the depressions
get stuck in mid – Atlantic. we have had stuck depressions mid
Atlantic since November and a continuous high over Scandinavia which
means high winds and rain in England and cold easterlies [...]
This from Robertscribbler
“Absolutely
true. Writing an article based on this, among other things, right
now. The Gulf Stream is very weak and continues to weaken....
...The
Gulf Stream has decreased in strength by about 10 to 15 percent since
2004. This is largely due to increasing melt outflows from Greenland
and due to ocean current changes in the Arctic and extreme North
Atlantic. Greenland melt is likely to continue to increase over the
coming decades. So we should see a continued weakening and southward
diversion of the Gulf Stream.”
Sam Carana of the Global Methane Emergency Group had a slightly different take
"What's
important is that the Gulf Stream keeps pushing warm salty water into
the Arctic Ocean, contributing to methane erupting from the seafloor
of the Arctic ocean, threatening to escalate into runaway warming."
I've got no argument with either point-of-view really, but in general I am in favour of explanations that can fit in multiple explanations rather than reduce everything down to one single cause.
The Global Methane Emergency Group are doing stirling work and I cannot argue with anything other than their firm advocacy of geoengineering as a techno-fix.
Their science is 100 per cent sound in my very humble opinion.
Their science is 100 per cent sound in my very humble opinion.
However, they are looking at just one positive, self-reinforcing feedback mechanism - methane release: there are many feedbacks that have been identified by Guy McPherson (I have lost count of how many - at least 25).
One of these is the weakening of thermohaline circulation.
There is today more confirmation that heat is the thing that will kill us all in the end, bringing to an end to conditions that are capable of supporting life, let alone agriculture and other aspects of human civilisation.
However, as the Arctic ice melts (and I suspect the next tipping point may be the disappearance of Arctic summer ice, replaced by dark water that absorbs, rather than reflecting sunlight) - we are sure to see a further weakening of the Gulf Stream, as well as in other areas such as the Antarctica.
This could indeed lead to a regional and temporary "ice age" before the heating takes over the entire globe.
This takes me back to the early 2000's - 2003 in particular when this scenario was first raised that melting of the Arctic ice would change the balance needed for the return of warm air to the north, giving rise to cold conditions in North America and Northern Europe.
This gave rise to a Hollywood blockbuster movie, The Day After Tomorrow which envisaged just such changes taking place, but in real time. It was rubbished at the time on the grounds that such changes would take decades.
Now that changes in the Arctic have been unleashed and we are seeing accelerated ice melt and associated climate change, we are, to all intents and purposes, seeing changes in real time. Months and years, not decades.
The Day after Tomorrow no longer seems SO ridiculous to those of us that are capable of embracing the truth.
The problem is that, in general we have such short memories. Most people can only remember what happened yesterday - not much further back than that.
Back
in 2003 two scientists, Peter
Schwartz and Doug Randall, published a paper, An
Abrupt Climate Change Scenario and Its Implications for United States
National Security.
This
laid out the scenario of abrupt climate change for the first time.
Below
are several articles, from the redoubtable the
Guardian, dating from 2003, discussing in terms that
are understandable the scenario of a rapid shutdown of the Gulf
Stream
Will global warming trigger a new ice age?
If
climate change disrupts ocean currents, things could get very chilly
round here, reports Bill McGuire
the Guardian,
13 November, 2003
13 November, 2003
If
you can remember back to the bitter winters of the late 1970s and
early 80s you might also recall that there was much discussion in
scientific circles at the time about whether or not the freezing
winter conditions were a portent of a new ice age.
Over
the past couple of decades such warnings have been drowned out by the
great global warming debate and by consideration of how society might
cope in future with a sweltering planet rather than an icebound one.
Seemingly, the fact that we are still within an interglacial period,
during which the ice has largely retreated to its polar fastnesses,
has been forgotten - and replaced with the commonly-held view that
one good thing you can say about global warming is that it will at
least stave off the return of the glaciers.
Is
this really true, or could the rapidly accelerating warming that we
are experiencing actually hasten the onset of a new ice age? A
growing body of evidence suggests that, at least for the UK and
western Europe, there is a serious risk of this happening - and soon.
The
problem lies with the ocean current known as the Gulf Stream, which
bathes the UK and north-west Europe in warm water carried northwards
from the Caribbean. It is the Gulf Stream, and associated currents,
that allow strawberries to thrive along the Norwegian coast, while at
comparable latitudes in Greenland glaciers wind their way right down
to sea level. The same currents permit palms to flourish in Cornwall
and the Hebrides, whereas across the ocean in Labrador, even
temperate vegetation struggles to survive. Without the Gulf Stream,
temperatures in the UK and north-west Europe would be five degrees
centigrade or so cooler, with bitter winters at least as fierce as
those of the so-called Little Ice Age in the 17th to 19th centuries.
The
Gulf Stream is part of a more complex system of currents known by a
number of different names, of which the rather cumbersome North
Atlantic Meridional Overturning Circulation (Namoc) is probably the
most apt. This incorporates not only the Gulf Stream but also the
cold return currents that convey water southwards again. As it
approaches the Arctic, the Gulf Stream loses heat and part of it
heads back to warmer climes along the coast of Greenland and eastern
Canada in the form of the cold, iceberg-laden current responsible for
the loss of the Titanic. Much, however, overturns - cooling and
sinking beneath the Nordic seas between Norway and Greenland, before
heading south again deep below the surface.
In
the past, the slowing of the Gulf Stream has been intimately linked
with dramatic regional cooling. Just 10,000 years ago, during a
climatic cold snap known as the Younger Dryas, the current was
severely weakened, causing northern European temperatures to fall by
as much as 10 degrees. Ten thousand years before that, at the height
of the last ice age, when most of the UK was reduced to a frozen
wasteland, the Gulf Stream had just two-thirds of the strength it has
now.
What's
worrying is that for some years now, global climate models have been
predicting a future weakening of the Gulf Stream as a consequence of
global warming. Such models visualise the disruption of the Namoc,
including the Gulf Stream, as a result of large-scale melting of
Arctic ice and the consequent pouring of huge volumes of fresh water
into the North Atlantic, in a century or two. New data suggest,
however, that we may not have to wait centuries, and in fact the
whole process may be happening already.
So
that the warm, saline surface waters of the Gulf Stream can continue
to push northwards, there must be a comparable, deep return current
of cold, dense water from the Nordic seas. Disturbingly, this return
current seems to have been slowing since the middle of the last
century. Bogi Hansen at the Faroese fisheries laboratory, and
colleagues in Scotland and Norway, have been monitoring the deep
outflow of cold water from the Nordic seas as it passes over the
submarine Greenland-Scotland ridge that straddles the North Atlantic
at this point. Their results show that the outflow has fallen by 20%
since 1950, which suggests a comparable reduced inflow from the Gulf
Stream.
Although
there is as yet no direct substantiation of this, and his colleagues
point to reports of the cooling and freshening of the Norwegian Sea
and to temperatures that are already falling in parts of the region
as possible evidence of contemporary Gulf Stream weakening.
It
also seems that it is not only the intensity of the outflow of cold
water that is changing. Bob Dickson of the Centre for Environment,
Fisheries, and Aquaculture Science at Lowestoft, and colleagues, have
reported a sustained and widespread freshening of returning deep
waters south of the Greenland-Scotland ridge, which appears to have
been going on for the past three or four decades.
Already
the freshening is extending along the North American eastern seaboard
towards the equator, in the so-called Deep Western Boundary current.
One
of the scariest aspects of the current dramatic changes occurring in
the system of North Atlantic currents is that the deep,
southward-flowing limb of the Namoc can be thought of as representing
the headwaters of the worldwide system of ocean currents known as the
Global Thermohaline Circulation. The possibility exists, therefore,
that a disruption of the Atlantic currents might have implications
far beyond a colder UK and north-west Europe, perhaps bringing
dramatic climatic changes to the entire planet.
Yet
again, this highlights the fact that global warming, for which we
have only ourselves to thank, is nothing more nor less than a great
planetary experiment, many of the outcomes of which we cannot
predict. Wallace Broecker, an ocean circulation researcher at New
York's Lamont-Doherty Earth observatory, described the situation
perfectly when he pointed out that "climate is an angry beast
and we are poking at it with sticks". Let's hope that when it
truly turns on us, its teeth don't match its outrage.
·
Bill McGuire is Benfield Professor of Geophysical Hazards and
director of the Benfield Hazard Research Centre at University College
London. He will appear on BBC2 Horizon's The Big Chill tonight
Alarm
over dramatic weakening of Gulf Stream
The powerful ocean current that bathes Britain and northern Europe in warm waters from the tropics has weakened dramatically in recent years, a consequence of global warming that could trigger more severe winters and cooler summers across the region, scientists warn today
1
December, 2005
Researchers
on a scientific expedition in the Atlantic Ocean measured the
strength of the current between Africa and the east coast of America
and found that the circulation has slowed by 30% since a previous
expedition 12 years ago.
The
current, which drives the Gulf Stream, delivers the equivalent of 1m
power stations-worth of energy to northern Europe, propping up
temperatures by 10C in some regions. The researchers found that the
circulation has weakened by 6m tonnes of water a second. Previous
expeditions to check the current flow in 1957, 1981 and 1992 found
only minor changes in its strength, although a slowing was picked up
in a further expedition in 1998. The decline prompted the scientists
to set up a £4.8m network of moored instruments in the Atlantic to
monitor changes in the current continuously.
The
network should also answer the pressing question of whether the
significant weakening of the current is a short-term variation, or
part of a more devastating long-term slowing of the flow.
If
the current remains as weak as it is, temperatures in Britain are
likely to drop by an average of 1C in the next decade, according to
Harry Bryden at the National Oceanography Centre in Southampton who
led the study. "Models show that if it shuts down completely, 20
years later, the temperature is 4C to 6C degrees cooler over the UK
and north-western Europe," Dr Bryden said.
Although
climate records suggest that the current has ground to a halt in the
distant past, the prospect of it shutting down entirely within the
century are extremely low, according to climate modellers.
The
current is essentially a huge oceanic conveyor belt that transports
heat from equatorial regions towards the Arctic circle. Warm surface
water coming up from the tropics gives off heat as it moves north
until eventually, it cools so much in northern waters that it sinks
and circulates back to the south. There it warms again, rises and
heads back north. The constant sinking in the north and rising in the
south drives the conveyor.
Global
warming weakens the circulation because increased meltwater from
Greenland and the Arctic icesheets along with greater river run-off
from Russia pour into the northern Atlantic and make it less saline
which in turn makes it harder for the cooler water to sink, in effect
slowing down the engine that drives the current.
The
researchers measured the strength of the current at a latitude of 25
degrees N and found that the volume of cold, deep water returning
south had dropped by 30%. At the same time, they measured a 30%
increase in the amount of surface water peeling off early from the
main northward current, suggesting far less was continuing up to
Britain and the rest of Europe. The report appears in the journal
Nature today.
Disruption
of the conveyor-belt current was the basis of the film The Day After
Tomorrow, which depicted a world thrown into chaos by a sudden and
dramatic drop in temperatures. That scenario was dismissed by
researchers as fantasy, because climate models suggest that the
current is unlikely to slow so suddenly.
Marec
Srokosz of the National Oceanographic Centre said: "The most
realistic part of the film is where the climatologists are talking to
the politicians and the politicians are saying 'we can't do anything
about it'."
Chris
West, director of the UK climate impacts programme at Oxford
University's centre for the environment, said: "The only way
computer models have managed to simulate an entire shutdown of the
current is to magic into existence millions of tonnes of fresh water
and dump it in the Atlantic. It's not clear where that water could
ever come from, even taking into account increased Greenland
melting."
Uncertainties
in climate change models mean that the overall impact on Britain of a
slowing down in the current are hard to pin down. "We know that
if the current slows down, it will lead to a drop in temperatures in
Britain and northern Europe of a few degrees, but the effect isn't
even over the seasons. Most of the cooling would be in the winter, so
the biggest impact would be much colder winters," said Tim
Osborn, of the University of East Anglia climatic research unit.
The
final impact of any cooling effect will depend on whether it
outweighs the global warming that, paradoxically, is driving it.
According to climate modellers, the drop in temperature caused by a
slowing of the Atlantic current will, in the long term, be swamped by
a more general warming of the atmosphere.
"If
this was happening in the absence of generally increasing
temperatures, I would be concerned," said Dr Smith. Any cooling
driven by a weakening of the Atlantic current would probably only
slow warming rather than cancel it out all together. Even if a
slowdown in the current put the brakes on warming over Britain and
parts of Europe, the impact would be felt more extremely elsewhere,
he said.
Climate
change: Gulf stream collapse could be like a disaster movie
The next Ice Age could take only weeks to engulf Britain. Scientists say the last great disruption to the Gulf Stream 12,800 years ago took only a couple of months to trigger a massive plunge in temperatures across Europe.
Robin McKie, Science Editor
,
29 November 2009
"It
was as if Europe had been shifted 20 degrees north and Ireland moved
to Svalbard," said Bill Patterson of Saskatchewan University.
In
the Hollywood blockbuster The Day After Tomorrow, an Ice Age was set
off in a single day when the Gulf Stream was disrupted. "That is
silly," said Patterson. "It couldn't happen that quickly.
However, previous estimates that it would take decades to switch off
the Gulf Stream are not backed by our work. It could happen in a
couple of months."
The
Gulf Stream carries tropical heat from the Caribbean to northern
Europe but is already being disrupted by meltwater pouring from the
Arctic as global warming intensifies. One day it may switch off
completely, say scientists.
Such
an event occurred 12,800 years ago when a vast lake – created from
melting glaciers at the end of last Ice Age – overflowed and poured
into the north Atlantic, blocking the Gulf Stream. Europe froze –
almost instantly, said Patterson.
His
team analysed mud samples from Lough Monreagh in Ireland and
discovered layers of white sediment made up of calcite crystals from
algae. "Then abruptly the sediment turned black. This stuff
contained no biological material." In other words, all life in
the lake had been extinguished in less than three months. "It
was very sudden," added Patterson, "and it could happen
again."
New
updates for earth.nullschool.net! Now you can see global ocean
surface currents in near real-time. Just click
here:
http://earth.nullschool.net/#current/ocean/surface/currents/orthographic
(A browser refresh may be required to pick up the changes.)
Earth & Space Research in Seattle, WA, produces this data every five days as part of the OSCAR project:
http://www.esr.org/oscar_index.html
http://earth.nullschool.net/#current/ocean/surface/currents/orthographic
(A browser refresh may be required to pick up the changes.)
Earth & Space Research in Seattle, WA, produces this data every five days as part of the OSCAR project:
http://www.esr.org/oscar_index.html
Also see this -
The
sudden cooling of Europe, triggered by collapse of the global
thermohaline circulation in the north Atlantic and the slowing of the
Gulf Stream has been popularised by the movies and the media. The
southern half of the global thermohaline circulation is as important
to global climate but has not been popularised. The global oceans'
coldest water, Antarctic bottom water forms in several key spots
around Antarctica. The water is so cold and dense that it spreads out
along the bottom all of the major ocean basins except the north
Atlantic and Arctic. Multiple recent reports provide strong evidence
that the formation of Antarctic bottom water has slowed dramatically
in response to massive subsurface melting of ice shelves and
glaciers. The meltwater is freshening a layer of water found between
depths of 50 and 150 meters. This lightened layer is impeding the
formation of Antarctic bottom water, causing the Antarctic half of
the global thermohaline circulation to falter
Thank you for the assembly of articles on a very important subject. I was born and grew up in the UK and still have family there and in any case I have a concern for the slowing of the Gulf Stream.
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