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earth's rising seas are some of the most

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visible signs of our warming planet over

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the last 20 years nasa's satellites

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airborne missions and field campaigns

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have shown a steady rise in global sea

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levels as the world's polar ice sheets

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melt here to tell us more about this is

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dr tom wagner from nasa's goddard space

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flight center um start by telling us you

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know you have some new images what do

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these new images show us

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about sea level rise you know they show

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us two really important things you know

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and the first thing is this sea levels

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are rising around the world and in the

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last 20 years they've risen by over

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three inches on average and we know this

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number really well it's actually

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recorded by a number of different

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satellites that go over the earth and

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bounce radar signals off the ocean to

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determine its height the other amazing

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thing though is that the ocean has

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topography you know you can almost think

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of it like a mountain range with peaks

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and valleys and the coast of california

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in this case actually is a little bit of

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a valley right now and this is caused by

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a combination of wind and ocean currents

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but what people really need to take away

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is that sea levels rising and it's going

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to continue to rise and it's rising

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enough that it's already impacting us

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what's causing sea levels to rise what's

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causing sea level rise are two basic

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things one is that as the planet warms

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up the volume of the ocean expands and

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that's about half of the sea level rise

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the other half comes from melting of ice

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that's on land in particular the

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glaciers and ice caps of alaska and

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canada and also the major ice sheets of

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greenland and antarctica and we have

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this other amazing satellite called

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grace which actually allows us to map

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changes in the weight of the ice sheets

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and what we found is that in the

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greenland case we're not only losing ice

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but the ice loss seems to be

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accelerating and that's something that

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we're trying to account for in our

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models as we move forward

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what is nasa doing to understand how

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much sea level could rise in the future

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nasa is doing three basic things you

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know one is we're developing the

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technologies

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to study sea level rise and then we're

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deploying them on satellites and also on

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aircraft to measure how fast the ocean

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is going up but we're also trying to

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understand the processes that are

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driving the ice loss and that's why we

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put scientists out in the field to study

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what's going on with the ice itself both

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on the ice and in the oceans around the

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ice because that's an important factor

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and then finally we pull all that data

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together into models and those models

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are important for us to understand the

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processes of ice loss and also to do the

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forecast into the future to kind of

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produce those numbers that society needs

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to plan for 10 50 100 years out

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and where can we learn more and see some

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of these images one of the best places

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to go is nasa.gov backslash earth where

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you can learn all about the work that

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we're doing right now the data sets that

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are available to see and also learn