Seymour solved the problem of separating ice from water in satellite altimeter signal. Seymour’s innovative research allowed him, other colleagues and myself, to use satellite altimetry over the ice covered Arctic Ocean, revealing, the Arctic Ocean’s gravity field, surface circulation, the thickness of its sea ice cover, and, more recently, how the changing ice cover might affect the coupling between the Arctic Ocean and the atmosphere. Seymour’s work provided evidence with which to propose and, eventually launch, the CryoSat mission. His paper describes the first results over Arctic sea ice from CryoSat-2.

The head line result from this paper is that Arctic sea ice volume has declined by 36 per cent in the autumn and 9 per cent in the winter between 2003 and 2012. The research, led by Seymour, used new data from CryoSat-2 satellite spanning 2010 to 2012, and data from NASA’s ICESat satellite from 2003 to 2008 to estimate the volume of sea ice in the Arctic.

The paper also provides the first observations of the annual cycle of sea ice growth throughout the Arctic Ocean and compares this seasonal cycle to output from the Panarctic Ice Ocean Modeling and Assimilation System (PIOMAS).  PIOMAS is based on a numerical model with ocean and ice components which is forced with NCEP Atmospheric Reanalysis data and assimilates other data to improve it’s ice thickness analysis. The animation shows the seasonal cycle of the sea ice volume estimates from CryoSat and PIOMAS.

Animation credit: CPOM/UCL/ESA/UW-APL/NSIDC/Planetary Visions

An interesting observation from this paper is that during the CryoSat time period (2010-2012) the winter ice growth is greater than during the ICESat time period (2003-2008). Averaged over the entire basin, this represents an extra ~36 cm of ice growth. Thin ice grows faster than thick ice in the winter, so this may explain why we see more growth during the winter in the later years. However, the increase in winter ice growth does not compensate for the summer melt and over all there is a decrease in sea ice volume between the two time periods.

A huge amount of effort went into validating the CryoSat-2 estimates of sea ice thickness and the paper involved collaboration between scientists from UCL, the European Space Agency, the Jet Propulsion Laboratory, the University of Washington, York University, Alfred Wegener Institute for Polar and Marine Research, Woods Hole Oceanographic Institution, Morgan State University and the University of Maryland.

The field work I described in the last series of blogs I posted here was part of that validation effort and I have picked a few photos from it to put here.

Photos: Top: Seymour (Photo from R. Willatt) inside the Twin Otter aeroplane as we travelled up to our base in the Arctic to take part in the CryoSat-2 validation experiments. He is taking the bottom photo which includes some of his co-authors (Christian Haas, Rosie Willatt, Malcolm Davidson and me).

Photo: The Polar-5 aircraft flying over one of our validation sites. It tows an instrument that measures ice thickness called an EM bird. It looks like a missile and flies about 10 meters above the ground (the aircraft is only flying at about 200 feet) so when it passes over you it feels like it is going to hit you. Data collected by instrument was used in Seymour’s paper to validate CryoSat’s estimates of ice thickness. (Photo credit R. Willatt)

Seymour would have been very proud and happy to see his paper published (and to read the BBC story about it by Jonathan Amos).

The paper has been published in Geophysical Research Letters and can be found here.

Banner photo credit R. Willatt.

We were all very happy to have got the break in the weather we needed to land at our sites on the Arctic Ocean and we were even luckier that the good weather continued at Alert and we made it out onto the fast ice site on both the 17^th and 18^th April. This time we travelled by skidoo. The ice has lots of lumps and bumps so some carful driving by Seymour made sure the radar got to the site in one piece, but from then on it didn’t go so well for the radar.

Photo: Beautiful day on the fast ice

Its operating temperature is 21°C, so there is a heating system inside its container. Usually it heats up pretty quickly, but we made the mistake of leaving it outside for an hour while we had our first hot lunch in days before we headed to the site. So it took much longer than usual to heat up. We spent a bit of time scouting out good test sites for it, then, just as it was approaching operating temperature our generator broke. Justin and Malcolm went to the rescue and headed back to the base to find a new one, while Rosie, Seymour and I got on with one of the snow depth surveys around a corner reflector. We eventually got it back up to temperature, but after already being out for 8 hours or so, it was getting very hard to keep our concentration and we decided to call it a day after taking a few calibration shots – which is definitely better than nothing.

Photo: Me making snow measurements with Stefan, underneath the radar (thanks Seymour for the photo)

The 18^th went much better. Stefan, from the Polar-5 team joined Seymour, Rosie and I on the ice, the radar kept it’s temperature well, the generator worked and we got all the measurements we were hoping to take the day before – and made it back for dinner. All in all it was a really good day on the ice and a great way to end our experiment.

Photo: Lunch time. I’ve had enough of frozen sandwiches. We kept these ones warm in the radar box – but it only takes about 5 mins exposure for them to become solid. (thanks Seymour for the photo)

There has been a pair of wolves roaming around the warehouse next to the airfield over the past couple of days. While we were waiting for permission to cross the airfield on our way to the fast ice site, one of them was basking in the sunshine next to us.

Today, just as we were about to leave in the Twin Otter for Resolute one of the wolves was hanging around, posing for photos. Justin left his rucksack on the ground, turned his back and the wolf nicked it. Luckily the wolf dropped it when Justin chased him.

The Polar-5 surprised us today on the south site. It tows an instrument that measures ice thickness, which looks like a missile, about 10 meters above the ground (the aircraft is only flying at about 200 feet). So when you see this thing coming towards you it looks like it will hit you! Here is the video of it – it takes about 30 seconds before you can see the plane in the distance coming towards you.

Yesterday we made it back to the north site after having to take a slight detour to wait on a different ice flow for a couple of hours until the cloud lifted enough for Troy and Derek to land on the ice. It’s pretty cold waiting in an unheated plane for that long, so it was great to finally land at our site. Despite having a shorter time on the ice than we hoped for we still got the corner reflector survey done and made some measurements with our ground radar.

Photo: Derek, Troy and Justin, still smiling after some very hard work dragging the radar sledge.

Today the conditions were perfect for landing and we managed to stay for 8 hours on the ice (in -30°C). We decided to start the radar surveys at the corner reflector site farthest away from the plane. Troy, Derek and Justin helped us drag it the 600 m or so through the snow (and back again!).

Photo: Blue ice on the ridge

There was a beautiful ridge at this site. Where two ice flows have been pushed together so the ice buckles up (and down) in large blocks, leaving exposed blocks of blue ice on the surface. This ridge had a deep cavity too, which was also spectacular.

Photos: Setting up the radar next to the plane, the cavity in the ridge

After eight hours in the cold I stopped feeling my toes and had to jump in to the plane to try and warm up while the others loaded up our kit. Derek kindly let me sit in the cockpit as it was a bit warmer in there. I think they’ve just about defrosted as I write this! This is a photo of Rosie at the end of our day on the ice, covered in frost.

So after checking the weather forecast again with Troy we went down to the airfield, loaded up the Twin Otter and were airborne by about 9.00 a.m (the top image is us loading up the Twin Otter). Due to the early start I managed to sleep all the way there and woke up when I felt the plane losing altitude. Troy and Derek were circling around the ice looking for a safe place to land, where the ice was thick enough to support our weight without us ending up in the ocean beneath. After a few low passes at about 15m to scout out the makeshift runway we landed pretty smoothly. You can see the landing in the video above. After we landed they taxied around for a bit to compress the snow and make a runway for us to take off from. This was my first ‘unseen’ (i.e. no one has ever been there before and one has test how thick the ice is) landing on sea ice and it was pretty exciting.

Photo: One end of our site marked by orange material and bin bags. You can just see the corner reflector behind the flag, which we use to line the site up).

Our first site was at 85.6° N 69.8° W, the furthest north I have ever been and will probably ever get to. The conditions were great around -25°C and not very windy, we set up the corner reflectors and marked their locations with large coloured sheets of material and bin bags full on snow, so Henriette and the other Twin Otter could see them from the air. Malcolm then used a satellite phone to call back to the base and tell the Henriette that they could leave to overfly our ground site, taking measurements with their airborne radar and laser. We also measured the ice we landed on – it was about 1.80 m thick (below is 100s of km of ocean).

Photo: Christian drilling through the ice to see how thick it was.

We then headed south again to 83.3°N 62°W to set up our second site. It was colder and windier here, but the set up went well again and the most important thing, we saw that the snow cover at the two sites appears to be different. This is important for our experiment as we want to see if the radar sees through the snow in the same way when the snow has different properties.

We only needed about 30 m of runway to take off from the second site as we were lighter after leaving the corner reflectors on the ice and we made it back to Alert for dinner. Rosie, Seymour and I have spent the rest of the evening making sure that our ground radar is working and as I’m typing this in the common room, Malcolm is using the data from the GPS buoys we put with the corner reflectors to track where they are moving as the ice moves.

P.S. I’m very tired while writting this so sorry if the grammer isn’t great!

Yesterday we spent an afternoon on the fast ice a few km from the base. Fast ice is a frozen bit of the ocean that is attached to the shore and doesn’t move. So you can reach it by skidoo, which is what we did yesterday. It was a beautifully sunny, clear day (the bad weather was where we wanted to fly to, not on the fast ice) and after winding our way through the blocks of ice, and stopping a few times to roll the skidoos back over when they hit the ice a bad angle, we found a suitable site to deploy the corner reflectors. It was a pleasure to be out there yesterday, unfortunately I forgot the battery for my camera so I have posted some of Seymour’s great photos in this blog. I think they show you what it was like better than I can tell you. We even saw Polar Bear tracks on our way back (see photo above), which is a bit scary – we make sure that we look out for them while we are working.

Today the conditions were nowhere near as good. The visibility was so poor that we couldn’t even skidoo down onto the fast ice again. Although the air temperature was only -23°C the wind chill was -37°C. We did go out near the base though to practice laying out the survey grid that is positioned around the corner reflectors and to see how long it took us to make some snow depth measurements (that’s what Justin and Rosie are doing in the photo above). All this is still useful to us, as when we do get out onto the Arctic Ocean itself we will have limited time on the ice before we have to get back into the plane and only one chance to get it right.

Photos: Waiting in departures; Justin, Rosie, Malcolm, Christian and Seymour, View from the Twin Otter

We got the all clear to leave for Alert at breakfast. So we headed for the airfield met our pilots for the next 10 days Troy and Derek, loaded up the Twin Otter with our bags and climbed onboard. The conditions were beautiful, clear skies and sunshine, which gave us fantastic views of this untouched scenery on route. Mountains covered by snow, glaciers and sea ice.

Photos: In flight entertainment, inside the Twin Otter

Travelling on the Twin Otter to the far north is an interesting experience. We travel in full Arctic kit, firstly, as the plane is very cold when you get on (it did warm up enough to take our jackets off) and secondly, you need to be in your kit in case you have to get out in a hurry. It took around 3 hours to fly to Eureka, were we had a quick stop to refuel and then another hour and a half to Alert.

Photos: Re-fuelling at Eureka, Jim and Kevin’s vans as we unloaded our kit

Alert is a military base but welcomes scientists who need to operate in the high Arctic and there is a great team of civilians also working here who are looking after us (Jim and Kevin). There is also a pack of wolves roaming around. Rosie and I spotted one on the road up to the base. It looked like a huge (they can be 6-7 feet long) white dog, surveying the land.  We’ve been told we have to be very careful not to encourage them onto the base as they might have rabies.

We spent the afternoon in a very cold warehouse sorting out our kit with the idea that we will fly tomorrow if the weather is good.