Monthly Archives: April 2011

Monitoring sea-ice conditions around Svalbard

From Mark (ESA), NL, 30 April

Over the next several days from 28 April–16 May, Arctic ice-thickness surveys will be taking place north of Svalbard, along CryoSat ground tracks.

Airborne measurements of sea-ice thickness are being conducted by the Norsk Polarinstitutt (NPI) in the sea-ice pack north of Svalbard using an EM-Bird from a ship-based helicopter, in combination with field teams taking measurements of ice thickness from the Norwegian vessel RV Lance.

Sea-ice concentration around Svalbare 20 April (credits: DTU/ESA/Polar View)

This AMSR-E satellite ice-concentration image shows the ice conditions north of Svalbard on 29 April, (Day 119) where this sea-ice component of the validation campaign is taking place.

The following ice chart from 28 April shows the corresponding interpretation of the sea-ice conditions by the Norwegian Met Service.

Ice chart showing sea-ice conditions on 28 April (credits: Norwegian Met Service)

Finally the plot below shows the CryoSat orbital ground tracks overlaid onto the map of the average April sea-ice edge in grey (and indicating the black outline of Svalbard). It also shows the days of potential airborne underflights of CryoSat by the AWI Polar-5 with EM-Bird and DTU Twin Otter with ASIRAS.  

CryoSat tracks over Svalbard 28 April to 5 May (credits: ESA)

The coloured legend with numbers indicates the digital dates of the coloured dotted CryoSat ground tracks, where day 118 = 28 April, day 121 = 1 May, and day 125 = 5 May.

The trick is for the ground teams to seek the best possible sea-ice location, over which the combination of coincident surface, airborne and satellite-borne data acquisitions are possible.

Naturally, we wish the NPI teams out on the sea ice the best of luck with the combination of sea ice and flight (visibility) conditions. Currently the perspectives look best to the northeast of Svalbard, where the ice conditions currently appear to be most favourable. Stay safe out there!

Austfonna ground control ready and waiting

From Thomas (UIO), Svalbard, 29 April

As various teams gather to kick off the measurement campaign around Svalbard, bad weather has delayed today's flights. Nevertheless, all the equipment is in place on the Austfonna ice cap and ready for when the weather is clear enough to fly.

One of the five corner reflectors on Austfonna (credits: T. Schuler)

A team of two from the University of Oslo spent the Easter week on Austfonna setting up the ground control points and preparing the base camp for the main campaign.

Five corner reflectors are now in place awaiting the overflight. As usual, conditions were difficult. This time, however, Easter brought surprisingly mild temperatures and rainfall all across the ice cap!

Maintenance work at an automatic weather station on Austfonna (credits: T. Schuler)

The resulting ice layer on top of the winter snow pack ensures an interesting stratigraphy. This layering will be studied in snow pits and by radar-profiling over the coming days by the main team. Four team members already out there working on the ice.

The remaining three team members are stuck in Longyearbyen due to bad weather and the overflight that was scheduled for today has unfortunately been postponed. Hopefully, the weather will clear soon and we can begin in earnest.

Back cruising through the sea ice

From Angelika (NPI), Arctic Ocean north of Svalbard, 29 April

After a week's break between cruises, the Norwegian Polar Institute sea ice group is out again for more work on the ice north of Svalbard.

Icebreaker KV Svalbard (credits: A. Renner)

Currently, we are waiting to get the helicopter for EM-bird flights onboard - cross your fingers that the clouds lift a bit!

A short trip into the pack ice yesterday showed us how different the ice edge is now. Only two weeks after our last station in the same area, there is now lots of broken ice, brash, and only small floes, which are difficult to work on and not really suitable for CryoSat calibration and validation work.

As soon as the helicopter arrives, we will head northeast to find some better ice for extensive stations, which will hopefully be coordinated with Polar-5 and Twin Otter overflights.

Kicking off a new round of measurements in Svalbard

From Tania (ESA), Svalbard, 28 April

I've arrived in a relatively balmy Svalbard; it's actually only 0°C, so not that cold. From the plane, I was able to watch the transition from a green snow-free Oslo to the completely white vista of Svalbard. So far, I haven't seen any polar bears – just this impressive landscape!

Svalbard (credits: T. Casal)

Lying between 74° and 81°N, the archipelago of Svalbard constitutes the northern most part of Norway – it's about midway between mainland Norway and the North Pole.

The team from the Technical University of Denmark also arrived this evening and the plan is to start this leg of the measurement campaign tomorrow over the Austfonna Ice Cap.

From the Norlandair Twin Otter plane we will be taking measurements from above while Jon Ove Hagen's team from the University of Oslo are busy gathering data on the ice below.

Looking forward to getting started!

NASA IceBridge flies Greenland EGIG line for CryoSat

From Michael (NASA), Greenland, 26 April

Today was our last opportunity to fly a science mission from Kangerlussuaq and the weather was favourable for Geikie 01, our last remaining high priority mission plan.

Geikie Plateau (credits: M. Studinger)

We expected some clouds over the interior of the ice sheet and down in the fjords and had to abort our flight up Nansen Fjord and Christian Gletscher because of a 3000 ft clouds base and 13 000 ft terrain.

Other than that, it was a perfect day. As the photo above shows, the razor sharp flood basalts of the Geikie Plateau are spectacular.

After we had finished the glacier runs around the Geikie Plateau, we went up Daugaard Jensen Glacier and continued on to the interior of the ice sheet back to Kangerlussuaq.

Daugaard Jensen Glacier calving front (credits: M. Studinger)

We flew along the EGIG (l’Expedition Glaciologique Internationale au Groenland) traverse route in support of ESA’s CryoSat campaign.

NASA IceBridge flight plan for 26 April (credits: M. Studinger)

The CryoSat-Validation and Calibration Experiment along the EGIG route is designed to provide ground truth data over the ice sheet for the airborne ASIRAS radar and CryoSat's SIRAL radar.

Geikie Plateau (credits: M. Studinger)

We will use IceBridge radar and laser altimeter measurements to link ground and satellite measurements to better quantify radar penetration issues over the various zones from the edge to the interior of the Greenland Ice Sheet.

Post adapted from Michael Studinger's NASA IceBridge flight report (F27/26 April)

Getting ready for a six-week stint living on the Greenland ice sheet

From Santiago (University of Edinburgh), UK, 22 April
 

Following the success of the first leg of the campaign in Canada, activities are about to continue over the Greenland ice sheet in a few days. This includes two teams from the UK that will living and working in central Greenland for the following six weeks.

The first team, led by Prof. Liz Morris from the Scott Polar Research Institute at the University of Cambridge, is already on the ice. Liz will be travelling by Skidoo from Summit Station down to a refuelling depot called simply T21.

Liz has been measuring snow and firn density over the Greenland ice sheet for several years using a neutron scattering probe. This instrument was originally designed to measure soil moisture, but has actually been very useful for measuring the bulk density of snow. The work done by Liz has extended the snow accumulation record to 25 years.

Area of Greenland to be surveyed by the UK teams (credits: S. de la Peña)

On 29 April, our team (Santiago de la Peña and John Pailthorpe) will be uplifted by a Twin Otter to a site known as T21. This a refuelling depot, located at about 2600 m above sea level on central Greenland. Here, we will meet with Liz for a couple of days before she leaves the ice sheet, leaving us two skidoos.

Very High Bandwidth radar in the field (credits: J. Scott)

We will ski down to a site located at an elevation of 2000 m, and then start our traverse that will take us to Summit Station, at 3200 m for 25 days. We will literally be living in the ice, under constant katabatic winds and temperatures ranging between –30 and –40° C. By the end of our little expedition, we will have travelled 600 km and surveyed more than 20 sites.

We will be using a Very High Bandwidth ground radar, which operates in a similar fashion to SIRAL and CryoSat's airborne equivalent ASIRAS, making snow density/stratigraphy measurements, taking infrared photography of snow structure, and assessing snow melt over the percolation zone of the ice sheet.

So what is so important to make us want to spend a month in such a harsh weather?

Well, for starters, measurement of snow density is crucial to interpret elevation changes as estimated by CryoSat in terms of mass change, and thus, fresh water input to the ocean and sea level rise.

ASIRAS profile over percolation zone of Greenland (credits: S. de la Peña)

Changes in the surface elevation of the ice do not necessarily produce changes in mass (for instance, seasonal densification may cause a negative elevation change, but no change in mass. Likewise, water from rain that refreezes in the snow, add mass to the glacier, but do not cause elevation changes).

Ice layers (credits: J. Scott)

The second objective is to characterize the radar response to a wide range of snow structures found over Greenland.

This is a crucial step for the interpretation of SIRAL signals, since the penetration depth of radar signals varies depending on snow structure, melt and accumulation.

The above images show ASIRAS profiles taken over the percolation zone of Greenland. Subsurface ice layers reflect radar signals better than the snow at surface.

Overall, we are very optimistic of the outcome of our expedition and, personally, I can’t wait for work to start next week.

Time to bid farewell to Alert

From Katharine (UCL), Alert, 19 April

Time to leave Alert now, but here's a quick update on the last couple of days here on the ice before we head off home.

The team before leaving for Resolute (credits: S. Laxon)

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 good weather continued to prevail at Alert. We were able to make it out onto the fast ice site on both the 17 and 18 April.

Beautiful day on the fast ice (credits: K. Giles)

The ice has lots of lump and bumps so some careful skidoo 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 we use on the ground.

The radar operates at 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 site, but just as it was approaching operating temperature our generator broke. Justin and Malcolm came 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 the radar back up to temperature, but after already being out for eight hours or so, it was becoming 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.

In a snow pit (credits: S. Laxon)

Monday 18 April went much better. Stephan, from the Polar-5 team joined Seymour, Rosie and I on the ice, the radar kept its temperature well, the generator worked and we got all the measurements we had hoped to take the day before – and made it back for dinner.

Lunch on the ice (credits: S. Laxon)

It was a really good day on the ice and a great way to end our experiment. We had lunch on the ice, but I’ve had enough of frozen sandwiches. We kept these ones warm in the radar box – but it only takes about 5 mins of them being exposed before they freeze solid.

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.

Arctic wolf at Alert base (credits: K. Giles)

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.

Fabulous photos of Greenland courtesy of NASA IceBridge

From Michael (NASA), Greenland, 19 April

Although not flying for CryoSat today, the following extract and photos from Michael Studinger's report provides some insight into the daily NASA IceBridge flights. IceBridge is the largest airborne survey of Earth's polar ice. As part of a collaborative effort between ESA and NASA, IceBridge is also contributing to the validation campaign for CryoSat.

Kangerdluqssuaq Glacier (credits: M. Studinger)

We are back from Flight 23 after another spectacular day over southeast Greenland and a very successful science mission. We accomplished longitudinal surveys along the center lines of Kangerdlugssuaq Glacier, Helheim Glacier, several branches of Midgard Glacier, and several glaciers nearby.

Kangerdluqssuaq Glacier (credits: M. Studinger)

This was an important mission to complete since the glaciers are all on the list of the big ones in Greenland and the area is difficult to fly. Midgard Glacier, which has changed rapidly in recent years, was of particular interest.

Midgard Glacier (credits: M. Studinger)

We also extended the survey lines in the fjords for gravity and magnetic data and were flying low at 600 ft and slow for better gravity data. Some of the icebergs in the fjords were around 700 ft tall.

I had a Landsat 7 image from the year 2000 on my laptop and was plotting the trajectory of the P-3 over the satellite image. It is amazing to see with your own eyes how much the calving fronts of most glaciers have retreated within 11 years.

Midgard Glacier (credits: M. Studinger)

All in all, we had a very successful day with an important mission on the books. We also very much enjoyed today’s flight!

 

Time to draw breath

From Seymour, Katharine & Rosie (UCL) in Alert, 18 April  

Ground work (credits: S. Laxon)

As the main activities in Alert are winding down, it's time to draw breath before the next leg of the campaign kicks off in Svalbard and Greenland. The UCL team has been looking back at what has been achieved over the last week.

After arriving in Alert, bad weather initially prevented the aircraft from flying to the experiment sites. However, a break in the weather and safe arrival of the DTU team with the precious ASIRAS instrument on 13 April meant that everything was in place to get the campaign off the ground.

Heading north (credits: S. Laxon)

The break in the weather held so that they were able to survey both experiment sites.

The northerly site is 85.58° N – less than 500 km from the North Pole. Landing here incurred several bounces as the plane touched down. After unloading, the plane then left to cool down its skis.

The skis get so hot during landing that if the plane just stops it will freeze solid to the ice, making it impossible to move again – clearly, not a good idea when you're 400 km from base.

Both sites were marked out with flags and then the corner reflectors are erected and tarpaulins placed on the ground to help the aircraft locate the line.

Setting up the ground radar (credits: K. Giles)

With the sites set up, the aircraft were able to make their survey flights over the following days. This includes the DTU Twin Otter carrying the ASIRAS instrument, the AWI Polar-5 towing the torpedo-shaped electromagnetic sensor and the NASA P-3 aircraft.

The Polar-5 flight proved a little disconcerting as the instrument hangs from the plane, just 10 m above the ground. The plane itself only flies at an altitude of about 200 ft while it's taking measurements.

Polar-5 towing the EM-Bird low over the ground (credits: S. Laxon)

Friday 15 April was a significant milestone in the campaign as the coordinated NASA underflight of CryoSat went perfectly.

It's been a pretty intense period and we've worked flat out in the hostile Arctic environment, and always at the mercy of incoming cloud.

This sometimes means waiting for the cloud to lift before the planes can take off and be sure of a safe landing on the precarious floating sea ice.

Although it's been a busy few days working in extremely cold conditions, the team did have a little time to take a few snaps, showing the beauty the Arctic holds.

For example, this was a beautiful ridge at the site formed as two ice floes push together.

Blue ice ridge (K. Giles)

The ice buckles up and down in large blocks, leaving exposed lumps of blue ice on the surface. The ridge also had a very deep cavity.

Ice ridge (credits: S. Laxon)

This photo shows one the Arctic wolves from the pack living around the Alert base.

Arctic wolf (credits: R. Willatt)

Keeping CryoSat on track

From Robert (ESA), 18 April, currently in the Lake District, UK

With all the excitement going on in the Arctic, one might think it’s business as usual back in Europe operating CryoSat’s main payload, SIRAL. Far from it; on top of the routine monitoring of CryoSat's health, there have been a number of background activities going on over the last few months to assure the success of the Arctic campaign.

CryoSat ground path (green) NASA P-3 path (yellow) (credits: R. Cullen)

First of all, we need to make sure SIRAL is being commanded as expected. The science measurement mode commands are transmitted to the satellite about a week before the radar is operated.

The team at ESA very confident that the automatic commanding is correct – as it has been since the facility that generates the commands was brought into operation early May last year.

Nevertheless, it’s worth a check during the critical period of a validation campaign.

Also, there’s CryoSat's orbital path to consider. Since the ground and air teams need to know to an accuracy of meters where the CryoSat ground track will be, it’s left to the experiment teams to determine this using the latest orbit predictions supplied from the Flight Dynamics Team based in ESA-ESOC, Germany.

The closer we do this to the CryoSat overpass, the more accurate the prediction is. Recently, there has been a lot of solar activity and this affects the accuracy of the prediction and how long it is valid for. It was therefore necessary to re-emphasise to the experiment teams the need to tune the air experiment flight plan as late as possible.

CryoSat's path on 15 April (credits: R. Cullen)

Furthermore, early last week it became clear that CryoSat was approaching its 'reference orbit dead band zone', which is an across track distance about the nominal reference for which CryoSat is kept to achieve its mission objectives. Ideally, one would want to avoid any maintenance manoeuvre to keep CryoSat as close as possible to its mission reference orbit. It became clear it was best to do this last Thursday to avoid a larger manoeuvre later in the campaign.

The first ground team activities with NASA and CryoSat under flights were planned for 15 and 17 April respectively, so it was a tough call for the Mission Manager to agree to the manoeuvre, albeit a necessary one.

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