The greenhouse effect may precipitate an ice age in Europe and the
There are corollary observations to what are described below involving
the melting of the arctic ice cap disrupting circulation of the Gulf Stream,
(This link may not come up so I have posted excerpts from the text
following the Daily Grist introduction and the ALANNA MITCHELL article.)
18 Dec 2003
Environmental news from GRIST MAGAZINE
Climate Change Alters Salt Levels in Atlantic Ocean, to Europe's Dismay
The Atlantic Ocean seems so vast that it's almost impossible to
imagine fundamentally altering it -- and yet, its salt levels have
changed so drastically over the last 40 years because of global
warming that the whole flow of ocean water is being disrupted,
according to a study published today in the journal Nature. As the
planet warms, more ocean water evaporates than normal, causing the
concentration of salt to increase in certain areas -- and, because
the overall salinity of the ocean must remain the same, to decrease
in others. Because salty water is heavier than fresh water, these
changes alter the way ocean water flows around the planet. In a kind
of vicious climate-change circle, that alteration will have its own
dramatic effects on the global climate, changing and redirecting such
basic forces as the Gulf Stream, which keeps places like England and
Ireland relatively warm and inhabitable, even though they share the
same latitude as the far colder southern Alaska. If ocean salinity
continues to change, the Nature study found, Northern Europe could
become as much as 10 to 20 degrees cooler than it is today.
straight to the source: The Globe and Mail, Alanna Mitchell, 18 Dec 2003
Atlantic's salt balance poses threat, study says
By ALANNA MITCHELL
Thursday, December 18, 2003 - Page A15
The delicate salt balance of the Atlantic Ocean has altered so
dramatically in the last four decades through global warming
that it is changing the very heat-conduction mechanism of the
ocean and stands to turn Northern Europe into a frigid zone.
The conclusions are from a study in the journal Nature that
is to be published today. The study describes planet-scale
changes in the regulatory function of the ocean that affect
precipitation, evaporation, fresh-water cycles and climate.
"This has the potential to change the circulation of the ocean
significantly in our lifetime," said Ruth Curry of the Woods
Hole Oceanographic Institution in Massachusetts, the study's
The study catalogues profound changes in the salinity of the
tropical and sub-tropical parts of the Atlantic Ocean. That part
of the ocean is becoming saltier because higher average global
temperatures are evaporating more ocean water than normal.
Over time, that water vapour travels north and south to the poles,
where it eventually replenishes colder oceans.
Because the overall salt content of the world's oceans is constant,
this means that as the equatorial ocean becomes saltier, the oceans
at the poles are becoming less salty and more fresh.
The implications of this are enormous. Until recently, scientists
had no idea how critical salt levels in the oceans are to the
hydrological cycle. They now understand that salinity is key
to the ocean's ability to move warm water around the planet.
Under normal conditions, the saltier waters of the far north and
south sink from the surface of the ocean to the deep abyss. Then
they are pulled along the bottom of the ocean back to the equator.
As that massive amount of water moves from north to south, warm
water from the southern Gulf Stream moves north closer to the
ocean's surface to fill the void. It's akin to a gigantic water
That warm water pulled up to the north also warms the air. It is
the reason England and Ireland are relatively balmy in winter
and not frigid like southern Alaska, which is at the same latitude,
said Professor Ransom Myers, holder of the Killam Chair in
Ocean Studies at Dalhousie University in Halifax and a
key researcher with the Census of Marine Life.
But as the waters of the far north become less salty, they lose
their ability to sink from the surface of the ocean to the abyss.
The conveyor belt is slowing down and may eventually stop.
"Northern Europe will likely experience a very significant cooling,"
Ms. Curry said, adding that it is expected to be in the order of 5 to
10 C cooler in winter in the course of 10 to 50 years, which is
considered to be extremely rapid climate change.
The trend in Europe will run counter to that of most of the planet,
which has been warming as greenhouse gases concentrate in the
The last time Northern Europe recorded temperatures that cold
was during the so-called little ice age that lasted from 1500 to
about 1800, she said.
If the ocean conveyor belt shuts down entirely, Northern Europe
will become as cold as Alaska and is unlikely to be able to support
as many people as it now does, Prof. Myers said. "We're changing
the Earth in ways that are just inconceivably large." he said.
The problem is that this change feeds on itself and scientists don't
know where it will stop, Ms. Curry explained.
When water evaporates more quickly in the tropics -- as it is now
from the effect of greenhouse gases that humans have emitted into
the atmosphere -- that water vapour creates a greenhouse effect that
helps to speed global climate change, including warming. In turn,
that increases evaporation, which increases the greenhouse effect.
And so on.
Melting of the arctic ice cap.....
"It could happen in 10 years," says Terrence Joyce, who chairs the
Woods Hole Physical Oceanography Department.
"As we continue to pile on atmospheric carbon dioxide, we're
going to have more unintended consequences," says William
Curry, a climate scientist. "We need to seriously consider steps
to curb greenhouse gases."
But first things first. Isn't the earth actually warming?
Indeed it is, says Joyce. In his cluttered office, full of soft
light from the foggy Cape Cod morning, he explains how
such warming could actually be the surprising culprit of the
next mini-ice age. The paradox is a result of the appearance
over the past 30 years in the North Atlantic of huge rivers of
freshwater-the equivalent of a 10-foot-thick layer-mixed
into the salty sea. No one is certain where the fresh torrents
are coming from, but a prime suspect is melting Arctic ice,
caused by a buildup of carbon dioxide in the atmosphere
that traps solar energy.
The freshwater trend is major news in ocean-science circles.
Bob Dickson, a British oceanographer who sounded an alarm
at a February conference in Honolulu, has termed the drop in
salinity and temperature in the Labrador Sea-a body of water
between northeastern Canada and Greenland that adjoins the
Atlantic-"arguably the largest full-depth changes observed
in the modern instrumental oceanographic record."
The trend could cause a little ice age by subverting the
the Gulf Stream, laden with heat soaked up in the tropics,
meanders up the east coasts of the United States and Canada.
As it flows northward, the stream surrenders heat to the air.
Because the prevailing North Atlantic winds blow eastward,
a lot of the heat wafts to Europe. That's why many scientists
believe winter temperatures on the Continent are as much
as 36 degrees Fahrenheit warmer than those in North America
at the same latitude. Frigid Boston, for example, lies at almost
precisely the same latitude as balmy Rome. And some scientists
say the heat also warms Americans and Canadians. "It's a
real mistake to think of this solely as a European phenomenon,"
Having given up its heat to the air, the now-cooler water
becomes denser and sinks into the North Atlantic by a mile
or more in a process oceanographers call thermohaline circulation.
This massive column of cascading cold is the main engine
powering a deepwater current called the Great Ocean
Conveyor that snakes through all the world's oceans.
But as the North Atlantic fills with freshwater, it grows
less dense, making the waters carried northward by the
Gulf Stream less able to sink. The new mass of relatively
fresh water sits on top of the ocean like a big thermal
blanket, threatening the thermohaline circulation. That in
turn could make the Gulf Stream slow or veer southward.
At some point, the whole system could simply shut down,
and do so quickly. "There is increasing evidence that we
are getting closer to a transition point, from which we can
jump to a new state. Small changes, such as a couple of
years of heavy precipitation or melting ice at high latitudes,
could yield a big response," says Joyce.
In her sunny office down the hall, oceanographer Ruth
Curry shows just how extensive the changes have already
become. "Look at this," she says, pointing to maps laid
out on her lab table. "Orange and yellow mean warmer and
saltier. Green and blue mean colder and fresher." The four-map
array shows the North Atlantic each decade since the 1960s.
With each subsequent map, green and blue spread farther;
even to the untrained eye, there's clearly something awry.
"It's not just in the Labrador Sea," she says. "This cold,
freshening area is now invading the deep waters of the
entire subtropical Atlantic."
"You have all this freshwater sitting at high latitudes,
and it can literally take hundreds of years to get rid of it,"
Joyce says. So while the globe as a whole gets warmer by
tiny fractions of 1 degree Fahrenheit annually, the North
Atlantic region could, in a decade, get up to 10 degrees
colder. What worries researchers at Woods Hole is that
history is on the side of rapid shutdown. They know it
has happened before. "