"Mammoth iceberg could alter ocean circulation: study"

From: http://news.yahoo.com/s/afp/20100225/sc_afp/climatewarmingglacierantarcticaiceberg

PARIS (AFP) – An iceberg the size of Luxembourg knocked loose from the Antarctic continent earlier this month could disrupt the ocean currents driving weather patterns around the globe, researchers said Thursday.

While the impact would not be felt for decades or longer, a slowdown in the production of colder, dense water could result in less temperate winters in the north Atlantic, they said.

The 2550 square-kilometre (985 square-mile) block broke off on February 12 or 13 from the Mertz Glacier Tongue, a 160-kilometer spit of floating ice protruding into the Southern Ocean from East Antarctica due south of Melbourne, researchers said.

Some 400 metres (1300 feet) thick, the iceberg could fill Sydney Harbour more than 100 times over.

...

"Obviously when there is warmer water, these ice tongues will become more fragile," said Legresy, who works at the Laboratory for Geophysics and Oceanographic Space Research in Toulouse, southern France.

http://en.wikipedia.org/wiki/Thermohaline_circulation

"The term thermohaline circulation (THC) refers to the part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents (such as the Gulf Stream) head polewards from the equatorial Atlantic Ocean, cooling all the while and eventually sinking at high latitudes (forming North Atlantic Deep Water). This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of around 1600 years) upwell in the North Pacific (Primeau, 2005). Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's ocean a global system. On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

"The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the meridional overturning circulation (often abbreviated as MOC). The term MOC, however, is more accurate and well defined, as it is difficult to separate the part of the circulation which is actually driven by temperature and salinity alone as opposed to other factors such as the wind. Temperature and salinity gradients can also lead to a circulation which does not add to the MOC itself."

Read the rest about how such things work.

A bit more from the news article:

"Since breaking off, the iceberg -- along with the newly mobile B9B, which is about the same size -- have moved into an ajoining area called a ploynya.

"Distributed across the Southern Ocean, ploynyas are zones that produce dense water, super cold and rich in salt, that sinks to the bottom of the sea and drives the conveyor-belt like circulation around the globe.

"If these icebergs move east and run aground, or drift north into warmer climes, they will have no impact on these currents.

"But if they stay in this area -- which is likely -- they could block the production of this dense water, essentially putting a lid on the polynya," Legresy explained."


As a totally unrelated bit of good news you might appreciate, the Antioch College revival project seems to be succeeding. Core principles re-affirmed. Teaching and co-op work ethic resumed, buildings being rehabbed, accreditation re-established: http://antiochcollege.org/ and http://alumni.antiochians.org/s/1050/start.aspx

The new president/grad has an absolute grasp on why it such a valuable teaching resource --> To repeat Matthew Derr's statement: “Antiochians know how to navigate the world with comfort. We feel comfortable in our own skins and with finding our way."

That was the best life lesson I could ever have learned, and, now looking backwards, nearly every good thing I experienced or did was something that would have not have been possible without Antioch and that lesson. Other routes and learnings, sure, would maybe yield some pride and more money, but nothing like what those words describe and the experiences and values that follow. I wish every school had work-study-travel as an intrinsic part, and a one year plus wander-year after or during. What a different world we would be.

(edit, because it is always something)

He'll plink it in his martini and take care of it.

It's been expected to calve for months.

But another iceberg ran into it and broke it free. *That* iceberg was the remains of an iceberg that calved in 1987, at about 2000 sq miles. http://www.guardian.co.uk/environment/2010/feb/26/antarctica-iceberg-global-ocean-circulation