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so what we're talking about is the

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Earth's northern polar icecap and what

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that's made of is ice that's floating on

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top of the Arctic Ocean

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and this is ice that's anywhere from

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like three feet at the thinnest to about

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20 feet at the maximum and we're

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interested in this ice for a couple of

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reasons the first thing is right now it

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functions like a giant mirror on the top

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of the planet and when sunlight comes in

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it reflects those rays of light back

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into space well ice has very different

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reflectivity than water water is a lot

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darker so as that ice retreats we get

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more dark water exposed now that

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incoming solar radiation gets absorbed

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and it heats up the water and that also

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increases the amp out of ice that melts

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now somebody need to understand too is

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that that ice is dynamic every winter it

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grows and continues out and then every

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summer it melts back the reason people

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are concerned right now is that in the

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past few years we've seen a dramatic

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summer melting that takes the ice back

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to a point that's far far far smaller

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than we've ever seen it before and in

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2009 we set the stage for another year

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of this continued melting and reaching

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what are near record lows this is

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important though not just because of how

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much ice we have in terms of extent the

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thickness of that ice is also important

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and in 2009 what we also released were

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some new satellite results where with

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first time were able to figure out what

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the thickness of the Arctic ice is all

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over the place and we're finding is that

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it's thinner now and that also thinner

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ice is easier to melt and thick ice and

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so all of this is setting the stage for

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predictions of an Arctic that is

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ice-free in summer months somewhere in

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the coming decades now we don't know

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when it's gonna happen but it's the

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kinda thing that a lot of people are

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working on trying to model but it's so

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obvious that this is happening that

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people that live in the Arctic regions

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and the countries that border the Arctic

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are planning facilities based on there

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being less ice there are people building

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warm water ports there are oil companies

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preparing to do exploration people

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talking about using it as a

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transportation route but also the Arctic

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people's that live there they're

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observing these change and they're

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saying things like hey we used to be

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able to walk out on the sea I

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and now we can't do that anymore so

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these changes are real and they're

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happening and what we're trying to do at

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NASA is like I say to go out and

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characterize this ice understand how it

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works how is it affected by ocean

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currents how is it affected by winds how

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is it affected by sunlight so that we

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can correlate that with the changes we

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see in the atmosphere and develop better

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predictive models we study the Arctic

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sea ice with a range of tools the most

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important tools are satellite tools you

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need to think of this ice as being

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continent scale okay this isn't

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something you can get with a single

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aircraft light and that's why NASA is

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really important because we operate the

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satellites you can study it with because

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from that we can tell what the

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concentration of ice is you know is it

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ice that's a foot thick that's covering

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everything or is it little patches of

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ice but that's not the whole story we

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also need detailed studies we're

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interested in how rough is the surface

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this ice is in some places it's smooth

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like that pond in the Midwest that

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freezes every winter but in other cases

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that ice has been blown and crunched

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together and we get ridges and mounds

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and things like that we also put people

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out there on the ground just walking

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around studying things we'll also study

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with aircraft and aircraft are great

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because the tools we can use an aircraft

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do different things and satellites or

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ground studies we map how much snow has

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fallen on the ice we try to measure the

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size of cracks as they were called

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leaves and put all that information

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together now why should you care if you

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don't live in the Arctic areas that's a

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really good question and the fact is

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this all this stuff we talk about when

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you retreat the ice cover and you heat

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the ocean up with more sunlight you also

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have to think about there's gonna be

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more water evaporating to the atmosphere

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there's a lot of other exchanges going

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on that's gonna change the way that the

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Earth's climate works and we expect

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weather patterns over in North America

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to change now this stuff is very very

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difficult to model but the most recent

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models suggest is that if we lose the

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Arctic ice cap we may have more droughts

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in North America so these are important