This summer's record melt suggests the Arctic may lose its ice
cap seasonally sooner than expected. What impacts can we expect?
On Sunday, September 16, the sun did not rise above the horizon in the
Arctic. Nevertheless enough of the sun's heat had poured over the North Pole
during the summer months to cause the
largest
loss of Arctic sea ice cover since satellite records began in the 1970s. The
record low 3.41 million square kilometers of ice shattered the previous low—4.17
million square kilometers—set in 2007. All told, since 1979, the Arctic sea ice
minimum extent has shrunk by more than 50 percent—and even greater amounts of
ice have been lost in the corresponding thinning of the ice, according to the
U.S. National Snow and Ice Data Center (NSIDC).
"There is much more open ocean than there used to be," says NSIDC research
scientist Walt Meier. "The volume is decreasing even faster than the extent [of
surface area] as best as we can tell," based on new satellite measurements and
thickness estimates provided by submarines.
Once
sea ice becomes thin enough, most or all of it may melt in a single
summer.
Some ice scientists have begun to think that the Arctic might be ice-free in
summer as soon as the end of this decade—leaving darker, heat-absorbing ocean
waters to replace the bright white
heat-reflecting sea ice. The
question is: Then what happens? Although the nature and extent of these rapid
changes are not yet fully understood by researchers, the impacts could range
from regional weather-pattern changes to global climate feedbacks that
exacerbate overall warming. As Meier says: "We expect there will be some
effect…but we can't say exactly what the impacts have been or will be in
future."
On thin ice
Arctic
ice influences atmospheric circulation and, hence, weather and climate. Take
away the ice and impacts seem sure to follow. There's more warming to come, as
well, particularly in the Arctic, which is warming faster than the rest of the
globe. Given cumulative greenhouse gas emissions, there's likely at least as
much warming to come as has occurred to date—a rise of 0.8 degree Celsius in
global average temperatures, most of that in the past 30 years.
The biggest impacts of the
loss
of Arctic sea ice, of course, will be felt locally: from the potential for
more snowfall (which can act like an insulating blanket keeping the ice warm and
incapable of growing) to more storms with stronger winds. These will also whip
up waves to pound the shore, eroding it, as well as bringing warmer temperatures
to thaw the permafrost—leading to "drunken" trees and buildings as well as
villages slipping into the sea. A loss of sea ice will also affect the largest
animals in the Arctic: seals, walruses and polar bears. "My people rely on that
ocean and we've seen some dramatic changes," said Inupiat leader Caroline Cannon
at a Greenpeace event on the Arctic in New York City on September 19. "We are
the gatekeepers of the ocean. We speak for the animals. They provide for us so
it's our time to speak for them," by arguing to ameliorate climate change.
Noting the climate change in Cannon's backyard, the rest of the globe is
indeed taking action—just not the type that could reduce greenhouse gas
emissions. "The world is looking at the Arctic as a new ocean to be developed
and exploited," notes Arctic system scientist David Barber of the University of
Manitoba, most particularly oil as evidenced by Shell's bid to drill the
first
offshore well in the Chukchi Sea. The U.S. Geological Survey estimates that
the Arctic holds an oil and gas bonanza—and companies from Russia to the U.S.
are lining up to start exploiting it.
But the dwindling sea ice may actually interfere with that effort. Shell's
bid to drill this year had to be
halted due to the
dangers of drifting ice. In fact, the reduction in sea ice actually makes
the Arctic Ocean more hazardous for oil exploration, not less, thanks to massive
chunks floating free and much more speedily than in the past. "Overall, sea ice
is becoming much more mobile," Barber says. On the other hand, shipping across
the Arctic Ocean has become viable for the first time—and weak or rotten ice, as
it is called, suggests a path across the topmost part of the planet is already
open for at least a short period of time. "We have already reached that point,"
Barber argues, based on three decades of field experiments on the ice.
The warmer Arctic waters and land have also begun to release methane, a
short-lived but potent greenhouse gas that is also the primary hydrocarbon in
natural gas fuel. The Arctic Ocean alone contains more methane than the rest of
the world's oceans combined—though when and even if such a
thawing would contribute a massive
methane release remains a "known unknown" in the words of former Defense
Secretary Donald Rumsfeld and oceanographer Wieslaw Maslowski of the Naval
Postgraduate School in Monterey. "If we release that methane, we will amplify
global warming by an unknown amount," Maslowski says. "We have no idea."
Global impacts
On a larger scale, the biggest impact may
be the changes in the Arctic's ability to function as a cooling system for the
global ocean. Both the Pacific and Atlantic now have
warmer
waters from the top to the bottom, based on
measurements
from computerized floats. The Arctic has been functioning as a global air
conditioner, losing roughly 350 watts of heat per square meter of open ocean to
the atmosphere during the fall storm season as well as the early part of the
winter. A warmer Arctic may not be able to shed those greater amounts of
heat.
That inability, in turn, will affect the temperature differences between the
northern polar region and areas further south. In the atmosphere, it is that
temperature gradient that creates and
sustains the jet stream—a
band of high winds at altitude flowing from west to east that typically steers
weather systems in the Northern Hemisphere. "The jet stream becomes more
kinked," NSIDC's Meier notes, which allows cold air to spill further south or
warm air to penetrate further north.
The loss of this temperature gradient may also
stall weather patterns within the
jet stream, allowing particular weather systems to park for a while in one
place. That may, in turn, create stronger heat waves and droughts or
precipitation. "If it's a rain pattern that gets stuck in place, you get
flooding that becomes a problem," Meier says.
Understanding these so-called "teleconnections" is an urgent area of
scientific rsearch, given the potential impacts on farming and other vital
pursuits. "Our society depends on stable agriculture," Barber notes. It is also
likely to be the one that people notice. As climate scientists Jennifer Francis
of Rutgers University and Stephen Vavrus of the University of Wisconsin–Madison
wrote in a paper laying out
how Arctic
warming might stall weather patterns via the jet stream: "Gradual warming of
the globe may not be noticed by most, but everyone—either directly or
indirectly—will be affected to some degree by changes in the frequency and
intensity of extreme weather events as greenhouse gases continue to accumulate
in the atmosphere."
Warming oceans globally will also allow for
more
thermal expansion of the waters themselves—the distance between liquid water
molecules rises as the water grows warmer. That will raise sea levels further
than the current roughly three millimeters per year.
Those warmer ocean waters are already lapping at the icy shores of Greenland,
speeding the melt of outlet glaciers for the massive ice sheet. Combined with
weather anomalies, like a heat wave that hit central Greenland this July and
temporarily
melted
nearly the entire ice sheet surface, this could presage a more precipitous
meltdown in the North. "Extreme melting from past years is preconditioning this
year's melt," says ice melt researcher Marco Tedesco of the City College of New
York, by melting away any accumulated snowfall from the winter sooner. "It's
like putting money in a bank account. If you start spending more money than you
put in, you go negative. That is what is happening on the ice sheet."
If Greenland were to melt entirely—which is still a distant prospect
according to most glaciologists' estimates—the ice sheet contains
enough water
to raise sea level by six meters globally. "How many people live within six
meter sea level rise of the coast?" Barber asks. "The answer is: too many."
Not all is lost
The seasonal loss of all "Arctic sea ice
is one of those tipping points and unfortunately we're going to pass that
tipping point," said
climate
scientist James Hansen, director of the NASA Goddard Institute for Space
Studies in New York City, at the same Greenpeace event. "I think we're going to
lose that sea ice. The good news is: this tipping point is reversible." Should
local conditions change, for whatever reason, however, it is possible the ice
could regrow.
After all, the ice spreads anew each cold, dark Arctic winter. Some
scientists and environmentalists have even suggested it might be
time
to attempt geoengineering of one form or another to restore the Arctic's
cooler temperatures. "We need to look at the possibility of [
solar
radiation management], which some people call
geoengineering,"
which could be an option to control or reverse the Arctic meltdown, argues
environmentalist Rafe Pomerance, former Deputy Assistant Secretary of State for
Environment and Development. "Effectiveness and
downsides and what the
risks are, we need to know all that." Cutting back on emissions of
greenhouse gases other than carbon dioxide—such as methane or black carbon—might
also have a bigger impact in the Arctic than elsewhere, given the role that soot
plays in melting ice.
There are potential positives to the loss of sea ice to consider as well.
Open ocean might permit
more carbon-absorbing
plankton to bloom, much as happens in the Southern Ocean around Antarctica.
"At this time, the Arctic Ocean is a biological desert," notes ecologist Louis
Fortier of Laval University in Quebec City. If the plankton blooms, the tiny
photosynthesizers pull carbon dioxide out of the air and can serve as the bottom
of a food chain that could create new and productive fisheries. Plus, if the
plankton die without being eaten or decomposed, they could bury CO2 with them as
the tiny corpses fall to the seafloor. In fact,
artificially
fertilizing such plankton blooms has been tried as a geoengineering
technique in the Southern Ocean, with some success.
But that success is unlikely to be repeated in a more watery Arctic Ocean.
The northerly sea is "already more productive [in terms of plankton] than the
ice-covered ocean of the near-past," says marine biologist Victor Smetacek of
the Alfred Wegener Institute for Polar and Marine Research in Germany, who
helped lead those
biological
sequestration experiments in the Southern Ocean. But local conditions, such
as a lack of nutrients and a lack of deep- and shallow-ocean water mixing,
suggest that the newly open waters of the Arctic Ocean are unlikely to produce
massive blooms, large fisheries or sequester CO2. "The CO2 sequestration
potential of the Arctic is very limited," Smetacek says. The Arctic will not
save itself.
Model failure
Regardless of what the Arctic meltdown
reveals, what is increasingly clear is that the
computer
models that scientists rely upon to make predictions have failed to capture
the rapid pace of change in the far north. The problem stems from spatial
resolutions that are too large—a single grid in a typical computer model
encompasses 100 square kilometers—to "see" small but important features such as
warm ocean water currents or ice export. And the computing capacity is
insufficient to render Arctic cyclones and the role they play in breaking up the
ice. "Are the
models still too
conservative or not?" Maslowski asks of the computer simulations that
underpin future predictions. "If this present trend continues, we might be
having almost no ice by the end of this decade."
Such a
total
summer loss of sea ice remains speculative at this point. "I wouldn't expect
it to keep going straight down," NSIDC's Meier says. "The ice that is remaining
may continue to stay thick even with more melt and that may be harder to get rid
of. The melt could plateau." At the very least, the sea ice is likely to rebound
next year, as has happened after every previous ice melt record. "That wouldn't
surprise me at all," Meier says.
What may surprise, however, are the global impacts of the already far
advanced loss of Arctic sea ice, particularly on the weather. "We need a few
more years of empirical evidence to give a confident answer," Hansen says of the
challenge of figuring out how the
Arctic meltdown will affect the
rest of the globe. Thanks to
ever
increasing greenhouse gas emissions trapping more and more heat, the world
will find out this winter—and for many years to come.
"There's evidence in the paleo-climate record that the
climate
system is capable of changing quite rapidly," Barber notes. "We're moving
into new territory and the impacts of that are unknown scientifically."
