Archive for June, 2011

Oh, and speaking of timelapse…

June 25, 2011

Speaking of timelapse videos, here are a couple of others that I quite like:

Sea ice near an Adelie Penguin colony. Shows the evolution of sea ice over a period of time (perhaps late spring and summer?) Partly I just like this because the motion of the tides makes it look like the ice is breathing.

Sea stars, urchins, Nemertean worms, and other denizens of the under-ice seafloor consume a seal carcass. Narrated by Sir David Attenborough! Not for the easily grossed out or those who are unsettled by crawly things.

Other people talk about ice!

June 25, 2011

I’ve been trying to do more with this blog than just write text and post it—WordPress offers a wide variety of features, and blogging is at its best when it’s part of a larger ecosystem rather than just one person talking in isolation. So I’ve been adding links to the blogroll. Allow me to present a few here:

From a Glacier’s Perspective offers detailed descriptions of glacier retreat around the world, with each post focusing on a different glacier. This post describes how a glacial feature called ogives can be used to help measure glacier velocity. (Ogives are “ripples” in the glacier that form due to the influence of icefalls: the area of ice that happens to be going over the icefall during the summer melt season melts faster than the ice around it, leaving a trough that then moves down the glacier.)

The IceBridge Blog recounts news from NASA’s IceBridge Campaign. The aerial surveys of IceBridge use a variety of instruments–lasers, radar, even a gravimeter–to survey the Earth’s ice. The information gathered from IceBridge will “bridge” the gap between IceSAT-1, which stopped taking data in 2009, and IceSAT-2, which is scheduled for launch in 2016. The blog includes both pretty pictures of icy landscapes and discussions of the science behind the work, such as this post on how airborne gravimetry can tell us about the shape of the land below water and ice.

For those of you wanting to see more of Antarctica (one of my favorite continents!) there’s the “Landsat Image Mosaic of Antarctica (LIMA)” which allows you to pan and zoom all over the continent. Anthony Powell’s photography shows the place on a slightly more intimate scale, mostly around McMurdo and including some justly famed timelapse films. Or Maria Coryell-Martin’s Expeditionary Art captures both the Antarctic and the Arctic, capturing the feel of the icy realms in a way photographs sometimes can’t.

I’ll be adding more as time goes along! In particular, I want to find some good resources on ice elsewhere in the solar system, which is a fascinating subject I haven’t even gone into yet.

One glacier, two glacier, fast glacier, blue glacier

June 20, 2011

Oneof the tricky bits about glaciology is distinguishing between different ice features. There’s the question of terminology, such as figuring out when an icefield (a large mass of glacial ice, often with many glaciers flowing out of it) becomes an ice cap (same thing, but larger and tending to be dome-shaped) becomes an ice sheet (like an ice cap, but over 50,000 square kilometers.) Today my dad (happy Father’s Day!) alerted me to an article in the Anchorage Daily News discussing the difficulties of counting glaciers.

Glaciers, like rivers and streams, often flow into each other or split apart. Exactly when one glacier becomes two glaciers can be a tricky thing to determine, and now that so many glaciers are retreating, these points of merging or splitting may disappear altogether. So what was one glacier with three branches might become three glaciers. For instance, in the photo below you can see how several tributaries merge into a single calving front at Columbia Glacier.

Columbia Glacier in 2004

Columbia Glacier in 2004. Photo by W. Tad Pfeffer.

(I got this photo from Wikimedia Commons.)

And here’s an amazing timelapse video from the Extreme Ice Survey (I’ve seen it shown at a lot of glaciologist meetings and conferences) that shows how the front of Columbia Glacier retreats back until the several “tributaries” start to look like separate glaciers again. It goes so far and so fast they have to move their camera several times so that the front of the glacier stays in the frame.

Of course, for many purposes, the important thing is not how many glaciers there are, but how much ice there is in the glaciers. Although there’s not very much water stored in mountain glaciers like these compared to the water stored in the great ice sheets of Antarctica and Greenland, the mountain glaciers are melting extremely quickly (well, quickly by glacial standards) so a major percentage of current sea level rise is due to meltwater from glaciers like the Columbia. You can’t tell how thick a glacier is just by looking, so determining the volume of the world’s glaciers—and just how fast that volume is changing—is one of the important ongoing problems in glaciology.

Feeding life, feeding back

June 16, 2011
A scanning electron microscope image of cells of Chaetoceros dichaeta, from Cefarelli et al. 2011.

A scanning electron microscope image of cells of Chaetoceros dichaeta, a type of diatom, from Cefarelli et al. 2011.

One of the most interesting aspects of climate dynamics is the role of feedbacks. There are two kinds of feedbacks, positive and negative. This earlier post about Snowball Earth describes a positive feedback, in which Effect One (the freezing of seawater) leads to Effect Two (the reflection of light back into space, which cools the planet) which in turn intensifies Effect One (more seawater freezes.) You can see a positive feedback effect at work in a more familiar environment when there’s a run on a bank: Effect One (the bank looks like it might fail) leads to Effect Two (depositors rush to get their money out of the bank) which strengthens Effect One (the bank, bleeding cash, now looks like it’s in even more trouble.) Positive feedbacks tend to make a system unstable. So they’re not really all that positive in the conversational sense of the word; in most systems, you want to avoid them.

This post, on the other hand, describes the carbonate weathering cycle–a negative feedback effect. In negative feedback, Effect One (warming of the planet from CO2) leads to Effect Two (weathering speeds up, removing CO2 from the air more quickly) which damps down Effect One (with less CO2, the planet cools down again.) Negative feedbacks make systems more stable.

Climate is an incredibly complicated system, with many feedbacks both positive and negative. This article at Science News, Melting icebergs fertilize ocean, describes the discovery of yet another one.

Living things in the ocean are limited by available nutrients, including iron. Some people think we should deliberately dump iron in the ocean to spur the growth of plankton that will suck CO2 from the atmosphere as they grow and then seal it away on the ocean floor when they die and sink to the bottom. Of course, many other people think that this is likely to have a lot of unintended consequences if we do enough of it to make a dent in atmospheric CO2.

But it turns out that icebergs in the Weddell Sea are already doing this, on a smaller scale. Glacier ice has a lot of iron in it compared to seawater, probably due to a combination of dust collected from the atmosphere and sediment from underneath the glacier. When icebergs break off the glacier and melt in the ocean, that iron is released, and thriving communities of algae and plankton spring up around the bergs. The more the planet warms, the faster glaciers flow and the more icebergs end up in the sea; the more icebergs there are, the more carbon gets soaked up by sea life, slowing down warming a little bit.

This effect is probably small compared to other feedbacks that are part of climate change, and it’s not very helpful from a human perspective, since each melting iceberg contributes to rising sea levels. But it’s always interesting to discover a new cog in the great machine of the Earth.

References:

Cefarelli, A.O., Vernet, M. & Ferrario, M.E., 2011. Phytoplankton composition and abundance in relation to free-floating Antarctic icebergs. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1436-1450.
Lin, H. et al., 2011. Free-drifting icebergs as sources of iron to the Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1392-1406.
Raiswell, R., 2011. Iceberg-hosted nanoparticulate Fe in the Southern Ocean: Mineralogy, origin, dissolution kinetics and source of bioavailable Fe.Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1364-1375.
Shaw, T.J. et al., 2011. Input, composition, and potential impact of terrigenous material from free-drifting icebergs in the Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1376-1383.
Smith Jr., K.L. et al., 2011. Carbon export associated with free-drifting icebergs in the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1485-1496.

The Voyage of the Endurance

June 11, 2011

Hey guys! I wrote you a song! It’s about the epic tale of survival that resulted from Shackleton’s attempted Trans-Antarctic Expedition; I used this website as a reference for some of the events, or you could read Shackleton’s own book on the experience, South. Be sure to check out the pictures, which are widely and deservedly regarded as the best part of the book.

Sung to the tune of (The Bonnie Ship) The Diamond.

The Voyage of the Endurance

‘Twas early in the century
The world prepared for war
But Shackleton intended the Antarctic to explore.
Some men sail for profit
Some sail for renown
But this one sailed for Science and the glory of the Crown.

Through the icebergs that clash, through the great waves that roll,
The mighty ship Endurance went a-sailing for the Pole.

The whalermen had warned them
That the ice would be severe
They were still above the Circle when the first floes did appear
Still bravely they sailed southward
But soon they were beset
Imprisoned in the heaving ice, but not defeated yet

Through the icebergs…

They whiled away the winter
Drifting ‘cross the Weddell Sea
When finally the sun arose, they thought they’d soon be free
But the mounting pressure of the ice
Was more than she could bear
In just days the stout Endurance was crushed beyond repair

Through the icebergs…

They loaded up the lifeboats
With provisions piled high
They watched her sink beneath the ice as, helpless, they stood by
The men camped on an icefloe
Let it take them where it would
It brought them near an island before breaking up for good.

Through the icebergs…

The isle was cold and barren
Inhospitable to man
So Shackleton devised another daring rescue plan.
He’d sail eight hundred miles
‘Cross the world’s most stormy sea
To the whalers on South Georgia he would make his earnest plea.

Through the icebergs…

A thousand times the pounding waves
Near sank the tiny boat
They lost most of their gear and food, yet somehow stayed afloat
When the party reached South Georgia
Thirst-tormented and sore
They realized the whaler-camp was on the further shore.

Through the icebergs…

They scaled the craggy mountains
And crossed crevasses deep
They stumbled into whaler-camp half-crazed from lack of sleep
The whalers were astonished
When these strange men came in view
Soon Shackleton secured a ship to rescue all his crew

Through the icebergs…

Let Shackleton’s Antarctic fame
For centuries survive
For with all their trials and troubles, every man came back alive!


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