100-Sq.-Mile Ice Island Breaks Off Greenland Glacier

suraj.sun sends word of a 100-sq.-mile (260-sq.-km) ice island that broke off of a Greenland glacier on Thursday. "The block of ice separated from the Petermann Glacier, on the north-west coast of Greenland. It is the largest Arctic iceberg to calve since 1962... The ice could become frozen in place over winter or escape into the waters between Greenland and Canada. ... [NASA satellite] images showed that Petermann Glacier lost about one-quarter of its 70-km-long (43-mile) floating ice shelf. There was enough fresh water locked up in the ice island to 'keep all US public tap water flowing for 120 days,' said Prof Muenchow." The Montreal Gazette has more details and implications for Canadian shipping and oil exploration, along with this telling detail: "the ice island’s thickness [is] more than 200 metres in some places... [or] half the height of the Empire State Building." The NY Times has a good satellite photo of the situation.

Comments

Re:Clearly a sign of AGW

[Rei]

Right, because global warming predicts that all weather will cease to exist, right?

Seriously, what sort of idiot thinks that there will be no randomness from year to year? Climate is about *averages*. And the trends are clear.

Re:In terms of rum & cokes,

[Sovetskysoyuz]

Volume of a 15 x 2 x 3 cm chocolate bar: 9e-5 cubic metres
Volume of an Olympic swimming pool: 2.5e3 cubic metres
Volume ratio is 1 : 2.78e7
Total volume of the oceans is 1.3e18 cubic metres
Iceberg volume, in the same ratio as chocolate bar : swimming pool, would be 4.68e10 cubic metres
If the iceberg is 200 m thick, then the area is 234 square kilometres.
The area of the iceberg, according to the article, is 260 square kilometres
O.o
You, sir, have astounding powers of estimation.

Re:Clearly a sign of AGW

[Rei]

If it's about averages, then you have to set the bar for the average. You can say a 30 year average is significant, or a 60 year average, or a 600 year average, or a 6,000 year average.

No, that would be called "making things up". Statistical significance requires statistical evidence. And we have ample evidence that the planet's temperature is dominated on the inter-annual scale by ENSO, and to a lesser extent, by other factors, but is dominated by AGW on the multi-decadal scale.

We have tons of data on ice extent. Most people know that, back to 1979, we have a beautiful record of satellite readings with only small holes. But there's a lot more.

Before that, we have sailing logs and logs from Arctic cities for the arrival and departure of ice. A particularly good source of data is the records from the US and Soviet navies' submarine fleets, which has been made available to researchers. There's direct written records from sailors all the way back to the dark ages, although these progressively become much patchier and are usually only good for localized ice extent.

From coastal records, the data dates back as far. Starting in the late 1800s, it becomes very good, and is near complete starting in the 1950s. Iceland has a good 1,200 year record.

Probably the best long-term record we have is that of sediment cores, and just recently we've started getting an increasingly number of papers on the subject (due to the hostility of the region, only readily have many cores become available). Here's a good review. There are several types of sediment proxies.

The first includes the deposition of ice-rafted debris. Large grains of minerals don't just appear in the middle of the ocean. They're too big to blow and too heavy to float. We observe the process of ice rafted debris being deposited in present day. The debris comes in two types: smaller grains from coastal margins, and larger grains from icebergs. The size, shapes, chemical signatures, and surface characteristics of the grains bear hallmarks of their origins and of the type of ice conditions at the time.

A second source of data in sediment cores is that of microfossils. Different types of plankton have different habitats in which they can live (i.e., some can live under ice, others can't) and known sedimentation and preservation rates. A third, and similar, technique involves the fossils of bottom-dwelling organisms. This may seem odd, as they're not directly affected by the ice -- but they're *hugely* indirectly affected. Very little organic matter, which such organisms eat, is deposited beneath the ice sheet; however, vast quantities are deposited around the edges of the ice, and a normal amount beyond it. Their populations are shown to well correlate with ice cover.

A fourth technique, like the above, involves the amount of organic matter itself deposited. Beyond just quantity, you can look at chemistry -- for example, there are chemical biomarkers for diatoms that live in sea ice.

At the coasts, you have a lot more data, as sea ice has significant affects on the land when it touches. This affects everything from whalebone to large mollusks to driftwood to plant matter and so forth. Even arctic tree records provide significant data, as arctic trees do not survive along coasts perennially lined with ice.

Concerning driftwood: wood cannot pass through ice. Driftwood floats, becomes waterlogged, and sinks in open water. Driftwood entrained in sea ice collects in quantity at the ice margin, and corresondingly sinks in quantity at such locations. Massive quantities of driftwood fossils are available.

Various types of sea mammals closely correspond with the ice margins -- polar bears, various species of seals, walrus, narwhal, beluga, and bowhead. T

Re:Clearly a sign of AGW

[Rei]

It's not true. The Earth warmed this much, and this fast, from 1900 to 1945

No, today's warming is faster.

The early 20th century warming is a combination of several factors -- first, a strong shift in the PDO, and then followed by not only a decline in PDO, but a rapid increase in global industrialization. The latter might seem like it would have just the opposite effect, but you have to remember that until the 1960s/1970s, there was very little regulations on power plant emissions. While CO2 causes warming, it has to accumulate for this to happen. Far more rapid is the cooling effects of chemicals like sulfur dioxide, which were emitted en masse until the first world started mandating scrubbers on its power plants. While SOx has a relatively short (compared to CO2) residency, so it's really just a masking of the real climate, its affects are quite powerful.