Ice dynamics, again

I’m once again compelled to point out that we know far less than we’d prefer about ice dynamics–all those melting and flowing and calving glaciers involving chunks of ice the size of various US states or (sometimes) small countries. The critical point is not just that we know less than “would be nice”, but that as we learn more we keep stumbling upon nasty discoveries that almost always tell us climate change is happening quicker and with more serious consequences “than previously thought”.

What’s doing said compelling this time around, you might well ask? The flurry of articles in the last day like this one: Mammoth iceberg could alter ocean circulation: study:

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.

…

The billion-tonne mass was dislodged by another, older iceberg, known as B9B, which split off in 1987.

Jammed against the Antarctic continent for more than 20 years, B9B smashed into the Metz tongue like a slow-motion battering ram after it began to drift.

Both natural cycles and manmade climate change contribute to the collapse ice shelves and glaciers.

Tide and ocean currents constantly beat against exposed areas, while longer summers and rising temperatures also take a toll.

…

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.

The Metz Glacier Polynya is particularly strong, and accounts for 20 percent of the “bottom water” in the world, he added.

(The best imagery I could find of this event was published by Yale Environment 360 here.)

My very first reaction upon reading articles related to the Mertz Glacier was something I can’t quote here, out of respect for the delicate sensibilities of some readers.

My second thought was, “Did we just discover a really major mechanism that’s part of how the environment responds to a swift warming cycle?” To be honest, I have no idea if this mechanism is news to experts, if it’s something that’s been speculated about and we’re only seeing it (potentially) happen for the first time, or if it’s an old concept that’s getting its 15 minutes of fame in the media. I doubt it’s the last two, simply because none of the articles I’ve seen mention those possibilities; but then I could be acting foolishly by trusting the media on such a nuanced point.