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  • >> This is a view of the earth that you probably not familiar

  • at looking at all the time,

  • looking down over the North Pole.

  • Here you've got the Arctic Ocean,

  • it's about 14 million square kilometers, and it's surrounded

  • by land on all of its sides, but then you have these regions

  • where water can flow in and out in here

  • through the Bering Strait, into the North Pacific, and then here

  • through Fram Strait and the Davis Strait

  • into the North Atlantic.

  • In the winter, the temperatures across the ocean on average get

  • down to about minus 30.

  • And because of these cold temperatures,

  • the sea waters freeze and it forms a layer

  • of ice known as sea ice.

  • And over average, the ice is about 2,

  • 2 and half meters thick,

  • and below it is kilometers of the ocean.

  • And in the winter, that ice completely fills the Arctic

  • basin and even reaches

  • out through the Bering Strait into the Bering Sea.

  • Now in the summer, that ice cover starts to retreat

  • as the temperatures get warmer and in the summer.

  • The average temperature across the Arctic Ocean is

  • around 0 degrees, and this video

  • that you've been watching here shows the summer September ice

  • extent minimum.

  • It's from the National Snow and Ice Data Center in the USA,

  • and some of you might be familiar

  • within the press every year around September,

  • you see headlines about we've reached another minimum arctic

  • sea ice extent, and it's a downward trend

  • since the satellite records began in 1979.

  • So, and then you often get kind of speculation

  • about when the arctic ice cuff is going to be ice-free

  • in this summer, and whether the Northwest Passage will be open.

  • And we can go back to PowerPoint now.

  • The [background noise], this is in the melting and freezing

  • of the ice [inaudible], that the ice kind of changes.

  • The ice is also moved around by the wind, it's dynamic.

  • And what you're looking at here is a video

  • that I took while I was on an ice company arctic.

  • And its two icebergs, basically being blown by the wind

  • and they crush in together, there's actually the sound

  • that you could hear, just before they lowered the volume,

  • was the sound of actually the ice [inaudible], the ice pushing

  • up against each other.

  • So as the ice is being moved around,

  • it's forming these ridges and it's thickening dynamically.

  • The other thing that happens as the ice moved is

  • that it splits apart, and again this was a picture I took during

  • an ice camp.

  • We've gone in for dinner into our mess tent and came out,

  • kind of-- just as the sun was setting and we were greeted

  • by this view about 100 meters from where we were camping.

  • The ice plain we were on had actually split in two,

  • so we're quite glad it hadn't happened straight on the center

  • of our camp, but it was an amazing view

  • and what happens here in the winter, because the warm--

  • the ocean is a lot warmer than the atmosphere.

  • It would lose heat to the atmosphere

  • and then ice-- new ice will form.

  • So these areas of open water become production areas

  • for the formation of ice.

  • So those figures I shared, or that animation I showed you

  • at the beginning, with the ice extent changing from year

  • to year, it's changing for 2 reasons,

  • one because it's melting or it's refreezing,

  • and the other thing 'cause it's changing dynamically.

  • So we don't just need to know how the area is changing,

  • we also really need to know how the ice thickness is changing,

  • 'cause then we can work out how the ice volume maybe changing.

  • Now sea ice has kind of an important role

  • in our climate system.

  • Something that you maybe familiar with it is this--

  • is the idea of the ice-albedo feedback mechanism.

  • So albedo is ma-- measure of the amount

  • of solar radiation that's reflected back in to space.

  • So sea ice covered by layer

  • of fresh snow has a very high albedo, about 0.9.

  • That means it reflects more radiation back into space

  • than the open water does and absorbs more radiation.

  • So when you have more [inaudible] from water,

  • more radiation is absorbed, you get more heating that can go

  • on to melt more ice and so on.

  • And of course the converse is true.

  • When you have more ice cover,

  • you get more radiation reflected,

  • and you can get cooling.

  • But this is isn't the only way the sea ice affects our climate.

  • It forms on the ocean so it forms a barrier

  • between the atmosphere and the ocean.

  • On the open ocean, the winds can free, they can't move the water,

  • but this isn't the case in the Arctic.

  • So that's another effect that it can have on,

  • on our climate system.

  • The third thing is that when it melts,

  • it adds fresh water into the ocean.

  • When it freezes, it add salt into the ocean.

  • So that can affect the density of the water,

  • but it's not just sea ice that's an important component

  • of the fresh water in the Arctic.

  • Now this diagram here describes a kind

  • of simple structure of the Arctic Ocean.

  • The sea ice actually fits in a very cool fresh layer

  • and that's separated from warm, salty Atlantic waters beneath,

  • by I think called the halocline.

  • So "halo" means salty and "cline" means slope.

  • It's a steep density gradient that's controlled by salinity

  • that separates these 2 very distinct water masses.

  • Now, I siad the sea ice forms contribution to that fresh water

  • in the top, but it's not just that.

  • In the beginning, you saw the map of the Arctic

  • and it was surrounded by continents.

  • And as you move in to the summer, these--

  • the rivers in those continents thaw and the river runoff runs

  • into the Arctic Ocean, and that provides another source

  • of fresh water, will also got cha--

  • changes from fresh water from precipitation and evaporation,

  • and also exchanges through those outlets that I showed you

  • into the North Pacific and North Atlantic.

  • And this diagram here is taken from a paper

  • and it shows the mean distribution

  • of that liquid fresh water in the Arctic.

  • And you'll notice it-- the red colors,

  • basically show we've got more of that fresh water

  • and that's predominantly in the Western Arctic.

  • So here you've got Greenland,

  • and this is the Canadian archipelago.

  • This is an area, notice the Canada basin

  • and it contains the Beaufort Gyre,

  • which is something I'm going to talk a bit more about later on.

  • Now we're interested in the storage and distribution

  • of this fresh water because if it is released even in parts,

  • it has the potential to disrupt the thermohaline circulation,

  • which then could have a knock-on effect

  • to our climate in Northern Europe.

  • So this slide is basically to summarize UCL's heritage

  • with working wit the European Space Agency to use satellites

  • to look at the changes in the Arctic.

  • This photo here was taken of the remote sensing group

  • at the Mullard Space Science Laboratory which is also known

  • as MSSS-- MSSL, and it's part of UCL.

  • This photo was taken about 20 years ago,

  • but actually our heritage with this kind of work starts,

  • even earlier than that, around the early 1980s, 1982 to 1983.

  • MSSL let us study for the European Space Agency,

  • looking at the feasibility of using satellites

  • to monitor changes in the Arctic.

  • But it wasn't really until the launch

  • of the Earth remote sensing satellites, which name is ERS1.

  • That was launched in 1991.

  • We can use data from 1993 onwards.

  • It wasn't until those satellites we launched

  • that we're actually able to have observations over the Arctic.

  • Previously, the satellites didn't go up that high,

  • we can actually see-- take data from there,

  • and it was really work done during this time

  • by Seymour Laxon who is sitting in the audience here

  • that pioneered the method that we used to calculate

  • or estimate sea ice thickness from space.

  • And I'm going to go on to the next few slides

  • and describe actually what this technique is

  • and how we're actually doing it.

  • So all of those satellites you saw were on the last slide,

  • and you carry an instrument known as a radar altimeter.

  • So the first bit of that is radar.

  • Now radar's a really useful tool for Earth observation.

  • This diagram here shows the opacity of the atmosphere

  • to different wavelengths of radiation.

  • And I'm sure you're all familiar with the idea

  • that an x-ray can see through your skin

  • and it can make a map with your bones.

  • Well, radar can see through our atmosphere.

  • It can see through the clouds and it can monitor what's going

  • on at the surface of the earth.

  • So that's why we use that frequency in Earth observation.

  • It also doesn't rely on having daylight,

  • which if you're using sort of an invisible wavelength,

  • then when it's dark, you're not going to see anything.

  • So it's useful for getting year-round measurements

  • over the earth.

  • Now the second word I mentioned was an altimeter.

  • Now this slide describes the measurement principle

  • for an altimeter.

  • And if you cast your mind back to your school days,

  • I'm sure you'll remember the relationship speed equals

  • distance over time, and that's basically what we're doing here.

  • The altimeter transmits a pulse of radiation, it travels to down

  • to the surface of the earth, it reflects to the surface,

  • and travels back up to the satellite.

  • And we measure the time taken for that pulse of radiation

  • to travel from the satellite to the earth and back again.

  • Now we know how fast the radiation is traveling.

  • We know the time, so from that we can work out the elevation

  • of the satellite above the surface that we've looking at.

  • So over the Arctic Ocean, we have the--

  • those areas of open water, the leads.

  • So we measure the elevation to the leads,

  • and then we measure the elevation

  • to the ice slopes next to them.

  • And if we take the difference between those measurements;

  • we can calculate the free board of the ice, so that's the amount

  • of ice, that sticky arc above the ocean surface.

  • Now, to kind of simply explain what we do next

  • to estimate ice thickness from this measurement,

  • the ice is floating and roughly nine tenths

  • of the ice is below the water level.

  • In reality, it's a little bit more complicated from this,

  • we have to take into consideration things

  • like the snow depth and density that's sitting on the top

  • of the ice and how it weights the ice down.

  • We have to consider the ice density

  • and the water density as well.

  • But that basically describes the principle of the measurement

  • and what were looking at.

  • Now, as I said today, I want

  • to present you our most recent results,

  • and I don't really have time to go into what we've looked

  • in the past, and though Seymour and myself had looked

  • at how the Arctic ice thickness has been changing,

  • but today just going to take the measurements over the ocean,

  • and this was actually started a couple of years ago

  • when we started looking at these ocean graphic measurements

  • on their own, and we noticed something was going on.

  • Now this is a video that's being made using our data.

  • The reds mean that the sea surface height is getting

  • higher, and we were looking at data between 1995 and 2010,

  • and what we could see is the sea surface height getting higher

  • and higher.

  • This area is in the Western Arctic, that area I pointed

  • out to you earlier where you get the largest storage

  • of fresh water.

  • So obviously after seeing this in the--

  • our data, we wanted to find out what was going on.

  • So our first port of call was to get and actually have a look

  • in the literature, and see what other people had been observing.

  • Now this figure here is from some work by [inaudible]

  • and what they've done is taken in situ measurements,

  • say measurements that should be made for being

  • on the Arctic Ocean, so from a ship or being in ice kind

  • of pool having a mooring floating around

  • or buoy floating around.

  • And here we've got data from 1992 to 1999.

  • There's some very small black dot from this plot

  • which actually show where the data are.

  • It's only data during the summer,

  • and that's because there's--

  • well there's not many measurements during kind

  • of Arctic winters, it's difficult to get

  • up to the Arctic when it's dark and it's so cold to actually

  • in situ observations, which is why satellites are really useful

  • because they can write kind

  • of a large scale view all year-round of what's going on.

  • So they collected measurements during the 1990s, and this group

  • of scientists then compared

  • that to measurements during the summer between 2006 and 2008,

  • and what you see when you just look at these two graphs,

  • this shows the amount of fresh water, and you can see here on,

  • here's the color scales,

  • so you're getting more fresh water in those later years.

  • This part here shows the difference between the two,

  • and when they added this up over the whole of the Arctic,

  • they got a number that was 8,400 cubic kilometers.

  • Now let's give you an idea of how much that was.

  • The figures I showed earlier with the fresh water

  • in the top layer of the Arctic Ocean, that contains

  • about 70,000 or just over 70,000 cubic kilometers.

  • If you are to amount all the sea ice, that would add

  • about 10,000 cubic kilometers.

  • So that number's kind of similar to the amount you'd have in all

  • of the sea ice, but it wasn't any of these guys

  • that as they always say, seen a change

  • in the fresh water storage.

  • This was another study done by some scientists,

  • and they had a hydrographic survey that took place in April

  • and March 2008, and they compared that to a climatology,

  • so a climatology just means like an average state,

  • and that average state was collected from or made

  • up from data collected between, I think, 1950s to the 1980s,

  • and there was another study

  • and they had 4 moorings again situated in the Western Arctic,

  • and they saw an increase in the fresh water during the Northeast

  • as well when they compare that back to the climatology,

  • I think, that was collected during 1950s.

  • So all of these data was pointing towards this,

  • they kind of snapped shots in time showing us

  • that something is changing in the Arctic,

  • the freshwater storage is changing.

  • Next thing a lot of these papers did was they used the models

  • to go and have a look at what was controlling that storage

  • of fresh water, and what these models told them was

  • that the wind was having an effect

  • on that storage and distribution.

  • Now this diagram here shows you what happens when the wind blows

  • on the ocean, so the thick, blue--

  • white arrows, that's the wind,

  • the thick blue arrows describe the average movement

  • of the wind-driven layer,

  • and thin blue arrows show the directions

  • of the surface current.

  • Now you might notice when you're looking at this figure,

  • the direction of the wind-driven layer,

  • the way of water is moving, is that right angle is to the way

  • that wind is blowing, and this was first spotted

  • by a Norwegian explorer and scientist Nansen and,

  • in the 1890s, Nansen decided he wanted to reach the North Pole

  • and he-- the way to do this was to sail his ship

  • which was called the "Fram," around kind of the Russian side

  • of the Arctic and let the Fram freeze into the ice

  • and then drift with the ice

  • and then hopefully the ice drift would take him

  • to the North Pole, so Nansen embarked on his voyage

  • and he would stay with his ship

  • for about a year while it was frozen into Arctic ice bank.

  • As they were drifting,

  • he noticed that the ice didn't drift

  • in the same direction as the wind.

  • It drifted kind of an angle 20 to 40 degrees to the side of it,

  • and when he finally returned from this kind

  • of epic adventure, he got back and explained what he'd seen

  • to other scientists and Ekman who I think was a Ph.D. student

  • at the time, came up with his theory of wind-driven currents

  • to explain the motion of the water in response

  • to the winds blowing on them.

  • So the average movement of that wind-driven layer is known

  • as the Ekman transport of water, and so you can see

  • in this situation here

  • where we've got anticyclonic circulation,

  • so there's winds blowing around in a clockwise direction

  • and you've got the water converging into the center

  • of the anticyclone, and that's making the water pile up

  • and that changes the sea surface height.

  • So that's that sea surface height here,

  • and that's something we can measure using our satellites.

  • On the other side, when you've got a more cyclonic circulation

  • system, you've got the opposite thing happening.

  • You've got the sea surface height lowering in the center

  • and then raising at the edges, and what the climate models

  • or the Arctic Ocean models showed was

  • that when you had the more anticyclonic circulation

  • where it seems fresh water was stored,

  • and then when you had more cyclonic

  • that fresh water was pushed to the margins

  • of that circular Arctic basin,

  • where it can be more readily released to the North Atlantic.

  • So what we can do now is take our sea surface height data,

  • and we can take some wind data,

  • and these 2 figures here show you this one here,

  • A is the trend in the sea surface height, so again that's

  • that Western Arctic, that's the Beaufort Gyre,

  • and this is a trend, so it's how the sea surface height is

  • changing through time, and what's happening here is

  • that you're getting an increasing domain of that gyre

  • and the center point's increasing height faster

  • than bits around the edges.

  • Now when you look at the other plot of what the wind is doing,

  • they're more blue, they're more negative,

  • means that the winds are becoming more anticyclonic,

  • so we've got, as we would expect

  • from what the models are predicting,

  • we've got the evidence for the sea surface height domain

  • and the winds becoming more anticyclonic, and then we--

  • when we [inaudible] the surface height data

  • and we did our calculations, we worked out that the change

  • in sea surface height due to, we'll say,

  • the change in the fresh water content due to the change

  • in sea surface height, was about 8,000 cubic kilometers,

  • so that fits in very well with what's been seen

  • in the in situ observations.

  • However, I wanted to look at this

  • in a little bit more detail, so I decided just to take

  • that Western Arctic region and average over it

  • on a year-by-year basis, and then look at how that rise

  • in the sea surface actually happened

  • on a year-to-year basis, and this is what you're looking

  • at on this graph here.

  • Now it's quite a lot to take in on this graph.

  • On the axis here, we have the sea surface height and that's

  • in pink, and then this side here we have the wind,

  • and that's in blue, and as the wind becomes--

  • as the trend here becomes more negative,

  • you get increasing anticyclonicity,

  • and what was really striking about this plot when we looked

  • to them, what surprised us a bit was,

  • it looks like there's 2 types of behavior going on here.

  • Now in the second half of our time period,

  • it looks like the relationship we'd expect, the wind is going

  • that way and sea surface height is going that way.

  • That's not just obvious in the first half of the time period.

  • I'll just clean up the graph a bit so it might make it,

  • kind of even more clear, so the obvious question

  • to us all is why is this happening?

  • Why are we not seeing this expected relationship

  • that we've kind of got the over--

  • evidence but when we look on a year-to year-basis,

  • it's not quite as simple as that, and there are a number

  • of different reasons you can think about.

  • Ekman transport and changes

  • in that Ekman transport aren't the only things

  • that control these storage of fresh water.

  • You could think about other things like kind

  • of [inaudible] water coming

  • in from the sides or changes in mixing.

  • But another, I think, quite interesting question is,

  • are changes in the ice cover affecting how the winds kind

  • of stir up the ocean?

  • Now earlier in the lecture,

  • I described to you how the Arctic sea ice forms a barrier

  • the atmosphere and the ocean, so that affects the transfer

  • of momentum between the atmosphere,

  • atmosphere in the ocean so it's peaceful that changes

  • in the sea ice cover could affect that transfer,

  • and then maybe towards the latter half of our time period,

  • the wind is becoming more efficient to spinning

  • up the ocean, and now there is actually other things

  • in the scientific literature that could also point

  • to this kind of change in the ice cover.

  • And there's the research done by a guy called Rampal who's looked

  • at the ice deformation rate so and how often you get things

  • like the leads forming and the ice cover,

  • how easy it is to move around.

  • And he's seen that during the year, during that latter half

  • of the time period that the deformation rate increased

  • and that implies that the mechanical strength

  • of the ice decreased, which sort of changed it's response

  • to the winds and the ocean currents.

  • So maybe there is something going on here,

  • and I think there's other another paper that was published

  • at the end of last year by a guy called Spreen,

  • who looked at changing ice velocities over the Arctic,

  • and talked about how the ice velocity can be fully explained

  • with what the wind was doing.

  • So I think there's other evidence that kind

  • of points towards perhaps something's going on here,

  • and in the future, this is a question I intend to go

  • and investigate further.

  • [Inaudible] and I'm being quite speculous here about the reasons

  • for that disparity I showed you in our last data report,

  • but I think it's a very interesting question.

  • And it's not just because it's the controls in the storage

  • and distribution of fresh water.

  • Now if you cast your mind back

  • to that schematic I showed you earlier, I showed you how the--

  • that cool fresh layer where the sea ice forms is separated

  • from the warm salty water, Atlantic water.

  • Now that warm salty water contains enough heat to melt all

  • of the Arctic sea ice in 4 years,

  • if it could get brought up to the surface.

  • So I think another question from this research is that,

  • if you've got a changing coupling between the atmosphere

  • and the ocean [inaudible] change in the ice cover,

  • could you increase the turbulent mixing in the ocean,

  • could you bring more of that heat up, and then could

  • that be another feedback to the ice [inaudible]?

  • And I think these are really interesting questions

  • that we can go on to look at with the satellite data

  • in the new observations from the CryoSat.

  • So now we're going to move on to CryoSat.

  • So in 1999, the European Space Agency put

  • out a quarter scientists and asked them to come

  • up with ideas, the satellites,

  • satellites that would monitor our environment or satellites

  • that could help tell us more about planet change.

  • And at UCO, a proposal was put forward

  • for a satellite called CryoSat.

  • It was led by Professor Duncan Wingham

  • and it also involved Seymour Laxon,

  • and they designed a satellite that would be dedicated

  • to monitoring the Polar Regions.

  • Everything I've shown you before from the ERS satellite

  • and MVSAT satellites which is work that I've been working

  • on previously, has been done with satellites that when sort

  • of optimized for looking at the Arctic or the Antarctic.

  • You may have notice in those plots I showed you,

  • showing the trends, there's a hole in the center

  • and that's not 'cause there's nothing there.

  • It's because the satellites don't monitor that high.

  • And CryoSat was different

  • because its orbit was different to those satellites.

  • It's designed to fill in that hole.

  • It goes all the way up to 88 degrees and it's a little bit--

  • it's also designed so it has a densest number

  • of sampling points in the Polar Regions.

  • But it's not just that that quite makes CryoSat different.

  • It carries an enhanced radar altimeter.

  • I'm not going to go into the details of how that works

  • but basically, it's processing

  • or the way it works it has the effect

  • of reducing the footprint on the ground.

  • Now by footprint, what I mean is if you imagine you had a torch,

  • so your torch has quite a small bit of like coming from here,

  • if I was to shine it at that wall,

  • you'd have a much larger area illuminated

  • on the wall 'cause the beam was diverging.

  • So if you imagine a satellite in space, it's transmitting a pulse

  • of radiation, but that diverges and when it reaches the ground,

  • the area that it's illuminating on a convention

  • or a territory is the order of kilometers.

  • However CryoSat employees enhance processing techniques

  • that reduces that area of illumination on the ground

  • to 300 meters and it's a cross track.

  • And that means that we get a better resolution

  • of measurement.

  • It should make it easier for us to pick

  • out those leads in the sea ice cover.

  • But it's not only that that it does.

  • It takes multiple shots, multiple looks at the same point

  • on the ground, so that means we can average all of those looks

  • to reduce the noise in our data.

  • And another advantage CryoSat-2 has is that when it's passing

  • over the ice sheets over Antarctica and Greenland,

  • it can measure the slope of the edges and that's where a lot

  • of the ice mass is lost.

  • So CryoSat-2 followed CryoSat-1 and I just finished my PhD

  • in 2005, and my first job as a post-doc was

  • to actually test the sea ice processing chain.

  • And in 2005, a group of us went to the one

  • of the European Space Agency bases to sit in a room

  • and watch the launch event live and watch the satellite go

  • up into space and this photo really is the last view

  • that we had of that satellite.

  • It was launched and we sat there--

  • this is us kind of sitting

  • in the room looking a little bit worried, and we waited

  • for about 15 minutes, after that time you expect the satellite

  • to send a signal back down to Earth to tell you

  • that it's in the orbit.

  • It's where it should be.

  • But that didn't happen.

  • So we waited another hour and still, still nothing

  • from the satellite and so by that point, of course,

  • through getting a bit worried,

  • and eventually I actually got a text from one

  • of my friends saying, "I'm sorry about your satellite."

  • And so they have-- they had somehow found out before I did,

  • but actually it had exploded on launch and when it was passing

  • over the Arctic actually.

  • But the European Space Agency quickly agreed

  • to build another version of the satellite, and in April 2010,

  • again we went to a European Space Agency base

  • and we were probably a little bit more nervous this time

  • after what had happened last time.

  • But I think you can probably see by the smiling faces

  • in this photo that actually this launch went well

  • and we are all absolutely delighted.

  • A few of those faces are from that photograph I showed you

  • from [inaudible] MSSO 20 years ago, Richard Francis was there

  • who was-- he now was European Space Agency's,

  • the mission manager for CryoSat, Duncan Wingham

  • who led the proposal, and so obviously we were all delighted

  • that that, it had gone well this time.

  • So following the launch at CryoSat,

  • it hasn't all stopped there.

  • UCL is still very involved with the way it was going on.

  • Not only will we be looking at the data and analyzing it

  • to look at how the Arctic and Antarctica is changing,

  • but we're also kind of making sure

  • that we really understand the data,

  • and part of that is validating our measurements

  • over the Arctic sea ice.

  • Now in April last year, myself, Seymour and [inaudible],

  • who is a PhD student in CPOM all went up to the Arctic

  • to actually take a radar and go

  • and investigate how the radar was penetrating

  • into the snow and ice cover.

  • And it was quite a complicated experiment, and what we wanted

  • to do was to be able to sample different ice types.

  • Now this part here is data from a guy called Christian Haas

  • and he was also heavily involved in organizing and participating

  • and designing this field experiment and he's

  • at the University of Alberta.

  • So this is data from an instrument called

  • electromagnetic bird.

  • It basically looks like a missile and it is towed

  • from an aircraft and it's tired so as it flies about 10 meters

  • above the ice and it transmits the signal

  • that then can be processed then from that week in

  • and measure the ice thickness from an aircraft.

  • And that's what this is, this is transects of an aircraft flying

  • out over the Arctic ice cover,

  • and the color codes show the thickness.

  • So you can see here it's thickened near the case.

  • This is Greenland, this is the Canadian Archipelago,

  • and if you fly out, it gets a bit thinner, and what we wanted

  • to do is sample that gradient and thickness.

  • So to do that, we had to get ourselves

  • up to a place called Alert, which is, sorry [inaudible],

  • she's about here, and it's a Canadian military base and then

  • from there, we got on to a small aircraft and we flew

  • out into the Arctic Ocean where we landed on the ocean

  • and on the frozen, on the ice, on the frozen ocean and got

  • to lock it out then did our experiments with our radar,

  • we did the ground surveys back in the plane

  • and then back to the base.

  • And we set up 2 sites, a North and South site on the ice

  • and a base as well on the ice

  • that was land far after the coast.

  • The other part of this experiment is

  • that it's difficult to take measurements that you make

  • on the ground, say, you got a radar and you're just looking

  • at the ground, it's maybe [inaudible] meters square

  • to something that you're observing from space

  • because of the different scales.

  • So another really important part of this field experiment was

  • to use aircraft to tie in the ground measurements

  • that we're making on the ground to the measurement

  • that CryoSat was making.

  • So not only did we have us on the ground,

  • we had aircraft flying over us

  • and then CryoSat flying over them.

  • So logistically, it was quite a big organization thing and a lot

  • of that organized by the European Space Agency.

  • So this Alert, you can't get a commercial flight there.

  • We had fly up and in with sort of [inaudible] aircraft

  • and you can see us all kind of packed into the aircraft,

  • with all our kits in the front,

  • and it's the [inaudible] most place on earth

  • where people actually live.

  • We're really dependent on weather when we do this.

  • We can't land on the ice if the visibility is poor.

  • Remember no one's been to where we're flying to before this.

  • No runway, and there has to be an instant

  • of them losing a plane through the ice before as well.

  • So the pilots need to make sure they can actually see what's

  • going on.

  • They can see if there's any lumps and bumps.

  • So this is Troy, our pilot.

  • He's kind of-- looking at the weather reports everyday

  • to see if we could fly.

  • On the days that we couldn't fly, we put everything,

  • all [inaudible] and went down to the ice that was grounded

  • to the coast and-- and kind of practice experiments as often,

  • experiments like that.

  • And we do spend time in the warehouses setting up our kit.

  • And these are polar bear tracks which I'm very glad to say

  • that we didn't actually see the bear

  • that made them 'cause it's something I particularly want

  • to come in to place contact with.

  • And but these little tracks next to it,

  • we're not quite sure what they were either.

  • Either it's this one or it was stalking something,

  • one of the team.

  • So when we finally could make it out and we set up two sites

  • in the ice, north and south site, we put out things

  • that like this bright orange tarpaulins

  • and bin bags for [inaudible].

  • So the aircraft, when they fly over, would have a target.

  • What is-- aircrafts are trying to hit these things,

  • they're called corner reflectors

  • and they provide a very bright target for the aircraft,

  • but they're difficult to spot when you're flying.

  • So putting things like this light bin bags,

  • just provides a simple target for them.

  • And here, one of our colleagues is also drilling through the ice

  • that we landed on to see how thick it was,

  • it was about 1.8 inches I think here.

  • And then as I mentioned, we also had the [inaudible] flights.

  • NASA, NASA had a plane up in the arctic during the time we're

  • there so they overflew as well

  • as the European Space Agency plane.

  • And around the lair as well, there's a pack of wolves,

  • they're-- are quite tame really and they pose very nicely

  • for photographs like this.

  • Well, the one other one was basically licking anything

  • that you'd left on the ground and hope

  • for finding food in there.

  • And this is our experiment site from the air,

  • so we try [inaudible] almost about 500 to a kilometer apart.

  • We've have 500 meters.

  • So we come-- so we tag these corner reflectors

  • and then we do dense snow surveys around them.

  • That graph that you see on this slide shows them,

  • our snow survey and shows how the snow varies

  • and we take our radar, we take measurements there.

  • We dig snow pits, we look at density, and we'll collate

  • in all these data so we can better understand how the radar

  • penetrates through the snow, which will depend

  • on the snow characteristics.

  • And this is just another going kind of shot,

  • I think that Rosie took and just showing our experiment site

  • and just after we've made all our survey lines,

  • and this is another shot of us showing, this is actually,

  • this a ridge, so that's when the ice is being pushed together,

  • and you're getting that dynamic thickening

  • and if you actually want to read a bit more about this experiment

  • and there's some blogs up at the European Space Agency web site.

  • And what I actually thought I'd show you next is,

  • it's going too advanced.

  • This is a video that shows you actually what it's like to land

  • on the ice, I think it's got sound on it as well.

  • [ Silence ]

  • The pilot would have done a couple of laps to check

  • that it looked okay before for he actually went in to land.

  • [ Noise ]

  • [Inaudible Remark]

  • [ Noise ]

  • So once the aircraft has landed, it will taxi around for a bit

  • to it actually flattened the snow

  • down to make sure we can take off again and also to make sure

  • that the skis don't freeze to the snow

  • and ice 'cause they quite warm once you come into land.

  • And then these next few shots might just give you an idea

  • of what it's like to be on the ice.

  • It shows the aircraft flying over the top of us.

  • You could put the sound back up.

  • [ Noise ]

  • [ Music ]

  • So just to summarize kind of what I've shown you today,

  • hopefully I've kind of introduced

  • to you UCL's highly long heritage with working

  • with the European Space Agency to use satellites

  • to monitor changes in the arctic, not only the Arctic

  • but the Antarctic as well.

  • And more recently, the research that are--

  • most recent discovery is

  • that it's not only the ice cover that's changing.

  • We're also being able observe changes

  • to the ocean's circulations

  • and that's revealing some interesting questions I think,

  • which is definitely something that I tend to look

  • into the future and try

  • to understand a bit better the physics

  • of actually what's going on.

  • I think UCL's involvement with CryoSat-2 is what hopefully,

  • you've se-- caught a glimpse of that by naming the full extent

  • of our involvement and there're numerous people

  • in our research group working very hard on looking at data

  • in CryoSat, and the map that's faded

  • out in the background here shows the ice thickness

  • for April 2011, and Seymour is hoping by April this year

  • that we should be able to have the first estimate of ice volume

  • since 2008, and that's should hopefully give us some

  • information about whether the volume

  • of the ice covering the ocean has been changing

  • over the recent years as well as the extent.

  • So, I'd like to thank you very much for your attention.

  • [ Applause ]

  • >> Thank you so much Katharine for such an exciting talk.

  • I think we have time for maybe one question, if anyone has any?

  • It's good.

  • Just run down the front and if you cold just wait for the mic

  • so they can hear you online.

  • >> I have one elementary question.

  • >> Okay.

  • >> Which is something that crops up whenever people talk

  • about the Arctic and or the Antarctic,

  • they talk about the West Arctic and one doesn't know

  • which direction is west when one is so close to the North Pole.

  • How is it related to the grand Meridian?

  • >> So when I talked about the West Arctic

  • and I would put [inaudible]

  • and moving towards Canada as-- as west.

  • That's-- that's how I think about it or how,

  • we don't typically describe it, and then east would be round,

  • kind of Russian and Siberian side.

  • >> Okay, I'm afraid that is all we've got time for today.

  • I want to thank you all for coming,

  • and I hope you could make some events this term and I would

  • like you to join me and thanking Dr. Katharine Giles.

  • [ Applause ]

>> This is a view of the earth that you probably not familiar

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從空間探索北極(2012年1月17日) (Exploring the Arctic from Space (17 Jan 2012))

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