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[music]

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NARRATION: Operation IceBridge has now returned to the Pine Island Glacier, not once,

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but twice in 2012. And the year-old

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giant crack in the glacier, poised to create an iceberg the size of New York City?

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Well it’s still there, and that iceberg has yet to break free.

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But the rift has grown longer, much wider, and spawned a secondary crack.

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Before we talk about when that mighty berg will be born,

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let’s take a look at the IceBridge missions themselves.

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IceBridge’s first return to the region was a high altitude flight over the entire region,

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including the Thwaites, Smith, and Kohler glaciers.

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After this campaign is over, scientists will be able to compare this broad survey

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with previous years’ measurements in order to better document the rapid and widespread changes

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in the region over time. For the second mission,

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NASA’s DC-8 flew, as it does for most IceBridge flights,

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at 500 meters above the ice, and this mission was about creating a brand new set of data.

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The flight lines took the team over previously unmeasured tributaries

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of the glacier, and also surveyed the bedrock below them,

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to provide a baseline for measuring change in the future.

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So why all this focus on the Pine Island region? NASA Goddard calving specialist Kelly Brunt

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says the ice in the region is substantially thinning and its flow is accelerating.

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BRUNT: Ultimately the change that we see

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in that whole region, not just Pine Island but also its neighbor, Thwaites Glacier,

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this change represents the largest input

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to sea level rise from an Antarctic source.

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NARRATION: The rift has been an intriguing phenomenon

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to watch over this last year, but is it a really important event?

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BRUNT: When we talk about Antarctica and we talk about

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the health and state of our ice sheets, we talk about mass balance.

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And what you have on one side of the equation is accumulation,

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or snowfall coming in. And when we talk about balance, that has to be balanced by things

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coming out. And in Antarctica that happens either through surface melt,

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or basal melt, or the big number, in Antarctica,

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is calving. Calving accounts for 80 percent of that side

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of the equation. So when you see calving in Antarctica, even

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even calving when we use small states or the island of Manhattan

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as a unit of measure – this is generally very normal – it’s part of the process.

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NARRATION: However, Brunt says once the glacier calves,

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the new calving front will be further upstream from any calving front we’ve seen in the last 40 years.

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BRUNT: I’ve used the analogy of a fingernail, to talk about calving.

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Generally, if your fingernail breaks

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in the white, it’s normal and you don’t worry about it.

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If your nail breaks below the white, you think about it, you remember it.

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If you lose your whole nail, that’s a big deal. Much of the calving,

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of the net loss through calving,

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can be equated to losing the white part of your fingernail.

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Things that we saw in the early 2000s in the Antarctic Peninsula side,

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the Larsen A the Larsen B … that’s equivalent to losing your whole nail.

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What’s going on in Pine Island is probably that intermediate.

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We’ve broken our nail and it’s below the white

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and it’s something to watch and it’s something to monitor over time.

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NARRATION: As a byproduct of the recent IceBridge flights,

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the team got some great views - and measurements - of the evolving crack,

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which has been filled in somewhat by blowing snow.

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The crack appears to only have a short distance to go before a new iceberg is born.

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It’s still hard to know when that will happen, but conditions seem to be right.

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BRUNT: Sea ice acts as a buttress or a

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dampener to sea swell that actually protects the front of these

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ice shelves or the front of these glaciers from calving. So the fact that there’s no

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sea ice in front of the Pine Island Glacier right now implies

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that it might be in a state that’s sort of primed to calve.

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NARRATION: After IceBridge heads back home from this campaign, its data will be used to monito

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the state of Antarctic ice sheets, while satellites will continue to watch