Ticking Along

After the endless problems of the first week, we’re now happily ticking along quite smoothly. We even managed to sort out a substitute for the failed Vaisala radiosounding system. Axel and Lars, the IT and electronics engineers on board, managed to build a very effective system from an old broad-band radio scanner, some downloaded software (COAA Sonde Monitor) produced by and for enthusiasts to receive radiosonde data in real time, some co-ax cable, a spare 12V power supply, some terminal block, and a capacitor (see below)

While we can’t do all the processing required to generate the WMO standards compliant messages required for use in initialising weather forecast models, we are able to get all the data required for later analysis. It’s amazing what can be achieved by people with the right skills and endless enthusiasm for solving other people’s problems.

Since we don’t have any web access, we couldn’t complete the online registration for the SondeMonitor software; a big thank you to its creator,  Bev Ewen-Smith, for sending us a registration ID by email.

A Long Week

It’s taken a while to get around to writing a first post from the
Arctic. The first few days on board are usually hectic as we reinstall
instrumentation, fire everything up, and then start trouble shooting the
inevitable problems. As first weeks of cruises go, this has not been one
of our better ones; we’ve suffered rather more technical problems than
usual. To make things more challenging, half of the problems are with
kit that we’re running on behalf of colleagues from other institutes,
and with which we’re not fully familiar.

We joined Oden in Longyearbyen on Svalbard last Monday (Aug 8). The
meteorology team – myself and John from Leeds, Piotr from Stockholm, and
Anna from SMHI in Norrkoping – immediately started sorting out all the
instrumentation that needed reinstalling. Most of the work was done back
in May, and all the sensors installed and tested, but we didn’t want to
leave them on the mast for the two months before the cruise started.

We got everything installed and powered up, and almost immediately found
our first problem. The Licor gas analyser, which makes water vapour
measurements, wasn’t starting up properly. We took the spare up, and
tested that: working! So, a complete swap of sensor and it’s interface box.

The next problem was the radio sounding kit. This is the ground station
for weather balloons. Data from weather balloons is used to initialise
weather forecast models, providing measurements of temperature,
humidity, and winds from the surface up to an altitude of about 25 km.
When we first ran through a dummy sounding – just running the radiosonde
on deck – to check the configuration of the system, we got no reception
of the radio signal. After several days of intermittently trying to get
this working – checking all the cables to antennas, double checking them
on a standalone radio receiver, etc, and many email exchanges with the
manufacturer’s engineers, we think the radio receiver card in the
sounding station has failed. A week on and we’re still testing and
trying out possible fixes but with no luck yet. This is a major blow to
the meteorology programme; there are very few direct measurements in the
Arctic, and forecast centres are always keen to get any they can.
Fortunately, it doesn’t actually impact most of the other science we’re
undertaking.

Meanwhile, back on the foremast another problem had cropped up. The
sonic anemometer – a sensor that uses pulses of sound to measure the
3-dimensional turbulent wind and air temperature – was outputting error
messages instead of data. The error messages indicated a mixture of
implausible measurements and a complete lack of signal on different
pairs of transducers. I initially thought this was a calibration
problem; the instrument was calibrated in a nice warm lab, worked OK
when first installed in May, but was now operating in sub-zero
temperatures. We tried to do a field-calibration on the lift platform
alongside the top of the mast, but with no luck. So, stripped it all off
the mast for tests back in the lab. So far we’ve failed to get it
working, but have determined that temperature changes affect which
transducers work and which don’t. Meanwhile we’ve installed another
sonic anemometer; this is working, but doesn’t have a heated head like
the first one, so if we get heavy icing conditions we’ll lose data.

Because most of the science on this cruise is piggy-backing on a
Canadian led sea-bed mapping expedition, we have to fit in around the
other work on board. We can only get up the mast when the ship is
stationary and conditions not too harsh. For the last couple of trips up
this has meant working between 11pm and 3am the following morning. Last
night’s trip up the mast was also pushing the limits of workable
conditions; with winds of 16 m/s we were swaying around rather more than
we were entirely comfortable with.

But for now at least, we’re finally getting the majority of the
measurements we really need. A great relief.

 

Returning to the Arctic

It has been a while – nearly two years – since the last post from the SWERUS cruise around the Arctic Ocean on Oden. We had a year off fieldwork last year, but are about to return to the Arctic Ocean, and the Oden, (probably) the best icebreaker in the world and certainly our favourite. We are participating in the Arctic Ocean 2016 expedition – a 6-week cruise that will take us to the North Pole, and down the Lomonosov Ridge towards Greenland.

We join the ship in Longyearbyen, on Svalbard, in a week’s time. There are several very different science projects sharing time on the ship – more on those later. I am leading a small team to study interactions between the atmosphere and sea-ice. In addition to myself and my post-doc John Prytherch we have two early career researchers: Anna Fitch (from the Swedish Meteorological and Hydrological Institute) and Piotr Kupiszewski (from ETH, Zurich and the Meteorological Institute, Stockholm University). All four of us will be posting updates here.

Another cruise blog is that of Runa Skarbø: https://runaskarbo.wordpress.com/

Ian.

Freeze Up

Summer has certainly ended here in the Arctic at 85N. The vernal equinox has passed and the sun stays very low in the sky all day, normally behind thick cloud.

Air temperatures have been between -2C and -7C depending on whether the wind is blowing onto or off the ice. Seawater temperature has been hovering around -1.5C, the approximate freezing point for water this saline (about 26 PSU, normal sea water is around 35 PSU).

We have been in mostly open water for the last couple of weeks but the conditions are causing the ocean surface to begin to freeze. This dramatically changes the appearance and behaviour of the ocean and is fascinating to see. It is also of scientific interest, as the interplay of air and water temperatures, winds and waves and the surface energy balance that affect the freeze up are complex and not well understood.

calm sea with grease ice at the surface

The first visible stage in sea ice formation is the formation of ‘grease ice’, a thin layer of ice at the surface, giving the ocean the appearance of being covered in a grey rubbery mat (Photo 1). In the presence of waves, either from wind, swell or the wake of a ship, the ice layer suppresses the smaller wind waves, but longer wind waves and swell are still present. The suppression makes the wave construction and interference less chaotic, and creates beautiful patterns in the water that look more like computer simulations than natural phenomena (Photo 2).

The ship’s walke supressed by grease ice

The next stage is the formation of pancake ice (Photo 3). Sometimes this is quite spread out, giving the ocean surface a mottled effect looking like the top of a whale shark. In the photo here, there is thicker multi-year ice in the background and the wind has blown the pancake ice onto it, pushing it together as if washing up on a beach.

pancake ice pushed up against multi-year pack ice

 

Wave Riding

The meteorology team on Oden is primarily interested in the ways that Arctic clouds influence sea ice, and vice versa. An important component of this is the sea state, the height and length of all the sea surface waves, in or close to the edge of the sea ice.

Waves influence the turbulent transfer of momentum and gases, such as CO2 and methane, between the air and water. The sea state is dependent on the wind speed, the distance the wind has blown over open water (termed the fetch) and on the presence of swell (longer period, more regular wave motion, typically created in a storm some distance away).

The presence of sea ice affects waves both by limiting the fetch, and by dampening the waves themselves. Waves in turn can break up the edge of the ice pack, and swell waves can travel into and through sea ice areas. All these interactions are quite poorly understood due to the difficulty of making good measurements in and around sea ice.

On Oden we are measuring the sea state using a Waverider buoy, deployed from the ship. The buoy floats on the sea surface, moving with the waves as they pass by. It uses instruments such as accelerometers to measure both the vertical wave motion (the heave) and the horizontal direction in which the waves are moving.

The waverider crew

Due to the presence of sea ice, which might trap the buoy, and for operational reasons, we can’t let the buoy free drift and so we are deploying it tethered, on a rope 200m long (including a snatch-chain between two floats to prevent Oden pulling on the buoy). We deploy it during stations, when the ship has stopped, and is putting instrumentation down to the sea floor to measure the sediments and/or the water properties. The stations usually last between 30 minutes and 3 hours.

buoy, waves, and ice

Deploying the buoy is straightforward – it is lowered over the side and allowed to drift away from the ship – actually it is the ship that drifts away from the buoy as the wind pushes on Oden like a large sail, and carries her away from the relatively stationary buoy. We then monitor the buoy while it is deployed to make sure it isn’t hit by any passing sea ice and that it doesn’t interfere with any of the other instruments and cables being lowered into the water nearby. To recover the buoy, the rope is simply pulled in – a good workout when time is tight and there is a lot of wave motion!

View from the waverider alongside Oden

 

buoy & gull

As well as our own science, we are also using the buoy to help calibrate Synthetic Aperture Radar (SAR) measurements made onboard satellites. SARs measure wave height and are typically tuned for open ocean conditions. Near-ice measurements such as those we are making help to better calibrate the sensors for Arctic regions. Coordinating a buoy deployment at the same time as when a satellite is overhead, and when winds and waves are high, isn’t always easy. When conditions are calmer, we at least get the opportunity for nice photos of Oden from the water.

The Oden from the waverider buoy

 

Ballooning

So as promised, a science post! As well as spotting wildlife and taking photos, the meteorology team on Oden are busy making measurements. One of the more hands-on of these are radiosondes, which we are responsible for launching four times a day, every six hours, throughout the 3 months of the cruise.

Radiosondes are a small instrument package, consisting of temperature, humidity and pressure sensors, plus a GPS antenna and an aerial for communicating the measurements back to the base station (Photo 1). The instrument package is attached to a balloon filled with helium, which rises through the atmosphere. As the balloon rises, the GPS enables wind speed to be estimated from the difference in position if the base station and the sonde.

A radiosonde

The instruments are used to get a profile up through the atmosphere, that is, a measurement of the variation in temperature, humidity and wind speed with height. The radiosonde is the workhorse instrument of meteorology and atmospheric physics; by directly measuring the profiles we can diagnose the physical state of the atmosphere at that location, obtain some of the key information required for weather forecasting and climate modelling, and calibrate remote sensors (such as those based on satellites, or the radiometers we have installed on Oden).

Filling the balloon

Launching a radiosonde involves setting the instrument up, filling the balloon, attaching the sonde to the balloon (Photo 2), then releasing it. Once the sounding has finished, usually because the balloon bursts (at a height of around 23 km for the balloons we use on Oden), the data is archived and then sent to meteorological agencies to be incorporated into weather forecasts. In normal conditions, preparing and launching a radiosonde is straightforward (Photo 3). On a moving ship with high winds, turbulent eddies from the ship’s superstructure, and freezing rain covering surfaces, including the balloon, with ice, things can be a little trickier (Photo 4).

Launching the balloon

Dan trying to stop Rez being launched with the balloon on a very windy day

For this cruise on Oden, we are particularly interested in conditions near the edge of sea ice areas, so we have been launching extra sondes in these locations. As there are very few radiosonde launches occurring in the region we are in, our radiosondes have a larger than usual impact on local forecasts, which in turn help the other scientists and crew on Oden to plan their work.

Gratuitous wildlife post

This is primarily a blog about science, and that was what I was intending this post to be. However, pretty much all real work on the Oden came to a halt for several hours yesterday when a couple of locals paid us a visit (Photos 1, 2 and 3).

Polar Bear and cub

 

Mum leads the way, on the hunt for herring (and scientists)

The polar bear and cub arrived while we were on station, i.e. stopped in approximately the same position, drifting with the ice, as various instruments were lowered down to the sea bed and back. The bears got close, 5 metres from the ship, perhaps attracted by the lunchtime smell of fried herring, and stayed long enough for many, many photos to be taken (Photo 4). And, well, they’re just too cute not to be worth a blog post. Science can wait!

Mum shows off her teeth. (Photo taken by Dan Wolfe)

It was a fantastic bit of luck to have bears come so close and stay for so long. While some of the crew were being necessarily cautious (the Oden’s flat stern could be climbed by a hungry enough bear, and was patrolled by the armed first mate), the other crew and scientists had a great, enjoyable afternoon, before heading off to the next station and a return to work.

bear watchers

I’ve already tweeted a couple of my own bear pictures, and Oden has many better photographers with very flash cameras and lenses. Björn Eriksson of Stockholm University and Dan Wolfe of NOAA have kindly let me post some of their pictures here.