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NARRATION: Operation IceBridge has now returned to the Pine Island Glacier, not once,
but twice in 2012. And the year-old
giant crack in the glacier, poised to create an iceberg the size of New York City?
Well it’s still there, and that iceberg has yet to break free.
But the rift has grown longer, much wider, and spawned a secondary crack.
Before we talk about when that mighty berg will be born,
let’s take a look at the IceBridge missions themselves.
IceBridge’s first return to the region was a high altitude flight over the entire region,
including the Thwaites, Smith, and Kohler glaciers.
After this campaign is over, scientists will be able to compare this broad survey
with previous years’ measurements in order to better document the rapid and widespread changes
in the region over time. For the second mission,
NASA’s DC-8 flew, as it does for most IceBridge flights,
at 500 meters above the ice, and this mission was about creating a brand new set of data.
The flight lines took the team over previously unmeasured tributaries
of the glacier, and also surveyed the bedrock below them,
to provide a baseline for measuring change in the future.
So why all this focus on the Pine Island region? NASA Goddard calving specialist Kelly Brunt
says the ice in the region is substantially thinning and its flow is accelerating.
BRUNT: Ultimately the change that we see
in that whole region, not just Pine Island but also its neighbor, Thwaites Glacier,
this change represents the largest input
to sea level rise from an Antarctic source.
NARRATION: The rift has been an intriguing phenomenon
to watch over this last year, but is it a really important event?
BRUNT: When we talk about Antarctica and we talk about
the health and state of our ice sheets, we talk about mass balance.
And what you have on one side of the equation is accumulation,
or snowfall coming in. And when we talk about balance, that has to be balanced by things
coming out. And in Antarctica that happens either through surface melt,
or basal melt, or the big number, in Antarctica,
is calving. Calving accounts for 80 percent of that side
of the equation. So when you see calving in Antarctica, even
even calving when we use small states or the island of Manhattan
as a unit of measure – this is generally very normal – it’s part of the process.
NARRATION: However, Brunt says once the glacier calves,
the new calving front will be further upstream from any calving front we’ve seen in the last 40 years.
BRUNT: I’ve used the analogy of a fingernail, to talk about calving.
Generally, if your fingernail breaks
in the white, it’s normal and you don’t worry about it.
If your nail breaks below the white, you think about it, you remember it.
If you lose your whole nail, that’s a big deal. Much of the calving,
of the net loss through calving,
can be equated to losing the white part of your fingernail.
Things that we saw in the early 2000s in the Antarctic Peninsula side,
the Larsen A the Larsen B … that’s equivalent to losing your whole nail.
What’s going on in Pine Island is probably that intermediate.
We’ve broken our nail and it’s below the white
and it’s something to watch and it’s something to monitor over time.
NARRATION: As a byproduct of the recent IceBridge flights,
the team got some great views - and measurements - of the evolving crack,
which has been filled in somewhat by blowing snow.
The crack appears to only have a short distance to go before a new iceberg is born.
It’s still hard to know when that will happen, but conditions seem to be right.
BRUNT: Sea ice acts as a buttress or a
dampener to sea swell that actually protects the front of these
ice shelves or the front of these glaciers from calving. So the fact that there’s no
sea ice in front of the Pine Island Glacier right now implies
that it might be in a state that’s sort of primed to calve.
NARRATION: After IceBridge heads back home from this campaign, its data will be used to monito
the state of Antarctic ice sheets, while satellites will continue to watch
the rift in the Pine Island Glacier as the melt season continues.
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