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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.

freeze up 1

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).

freeze2

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.

freeze3

pancake ice pushed up against multi-year pack ice

 

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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

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

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

View from the waverider alongside Oden

 

buoy & gull

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

The Oden from the waverider buoy

 

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

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

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).

Barbara launching a balloon during a pleasant Arctic morning. (Photo by Dan Wolfe)

Launching the balloon

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

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.

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 (Photo by Björn Eriksson)

Polar Bear and cub

 

 Mum leads the way, on the hunt for herring (and scientists) (Photo by Björn Eriksson)

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)

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

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.

On Thursday what we’d all been waiting for was spotted: the first Polar Bears of SWERUS-C3 Leg 2! The first one was pretty far off, I only saw it through binoculars, but still, very exciting. The second one came much closer and most of the ship got a look and a photo.

ola bear

Polar bear

This bear photo was taken by Ola Persson, leader of the Leg 2 meteorology team. Ola has been taking some great photos on the cruise, and I’ve included a couple more of my favourites here. The first is from the open-ocean work that began Leg 2, in the Chukchi Sea north of the Bering Straight (Photo 2). A series of low pressure systems built up the wind and waves in the area, as dramatically shown in the photo. Conditions onboard got a touch uncomfortable, Oden is much happier breaking ice.

bow wave

bow wave

The photo also gives a nice view of some of the instrumentation the met’ team has installed on Oden for this expedition. On the bow is the flux mast, with sonic anemometers for measuring 3D wind speeds, plus temperature and humidity sensors, at the top of the mast and at the mid point. These are my main area of scientific interest and I will probably talk about the mast more in a later post.

On the roof of the port (left) side container, partially contained in a metal cage, is the scanning aerosol Doppler LiDAR, from which we get information on cloud layers, plus aerosols and turbulence. The metal cage has motors and motion sensors and is used to counteract the movement of the ship and keep the LiDAR level. On the roof of the white container is the opening (covered in plastic sheeting) for the W-band radar. This is also motion-stabilised and gives us information on clouds. Finally, the white poles making a grid structure are the 449 MHz profiling radar, the only one of its kind deployed on a ship, which is used to measure the wind profile, i.e. the changing wind speeds up to a height of at least 3-4 km.

The final photo I’ve included is one of Dan and I looking out from Oden’s bow at passing ice. It nicely shows the beguiling nature of the ice, the complex and varying shapes and range of colours that make the Arctic a beautiful as well as a harsh environment.

ice

ice

The meteorology team for the second leg of the SWERUS-C3 / ACSE Arctic cruise is shown in Photo 1, sporting snazzy windbreakers from our Swedish hosts.

While we all have slightly different responsibilities, we work closely together and help each other out with our various jobs. A cruise like this is a great opportunity to develop new skills by getting to put them into practice, and I’m very lucky to be working with such experienced, skilled (and fun) colleagues.

The leg-2 meteorology team: Ola, Dan, John, Barbara, and Georgia

The leg-2 meteorology team: Ola, Dan, John, Barbara, and Georgia

As an introduction, we’ve all put together a paragraph or two about ourselves. These are below, lightly edited by me (I claim any spelling/grammar errors).

Ola –
Ola Persson is a seasoned Arctic researcher with NOAA’s ESRL/PSD/Weather and Climate Physics Branch out of Boulder, CO and team leader for the Boundary-Layer Meteorology Team. His specific interests are in the interactions between the atmosphere, ocean and sea ice along the ice edge, or marginal ice zone, including those associated with clouds, mesoscale dynamics, and ocean waves. As team leader he is responsible for making sure that our scientific interests continued to be met throughout the cruise. Ola was born in Sweden moving to the US at the age of 8, though his home in the U.S. had a very strong Swedish flavor to it. He has returned numerous times to Sweden to visit relatives and work for periods of a few months to a few years. His Arctic interests began with a summer job he had working as a field assistant at the University of Stockholm’s Tarfala glaciology station in northern Sweden, where he made surface radiation, mass balance, and runoff measurements on the glaciers. This job was arranged for him by Bert Bolin, a famous Swedish meteorologist who has given his name to the research center in Stockholm and who was a former folkdance partner of Ola’s mother. Besides being a great liaison he has provided us with some insights to the crew and things that are foreign to the rest of us.

Barbara –
Barbara Brooks is from the UK’s National Centre for Atmospheric Science (NCAS) and is based at the University of Leeds, UK. She has fingers in a number of instrument pies, primarily the atmospheric sounding system, LiDAR, and Radiometer, but is also helping out in the running of the Leeds flux mast and Waverider buoy. In her spare time she is also baby sitting the methane measuring system from Stockholm University that ran on the first leg. Her husband Ian Brooks [who runs this blog} was on the ‘Met Team’ for leg 1 and they managed to say hello during the crew change over in Barrow. This is the first time she’s actually sailed on ODEN: during the 2008 ASCOS project she had instrumentation deployed on the ship but spent the project flying over it in the NASA DC8 research aircraft along with Ola as part of the AMISA project.

Dan –
Dan Wolfe “Grandfather of the BAO”, though semi-retired, volunteered for this research cruise with the desire to explore a part of the Arctic he’d never seen. He first came to the Arctic in 1970 on board the U.S. Coast Guard Icebreaker Glacier as part of WEBSEC, a baseline study north of the Western Beaufort Sea prior to the Alaska pipeline. It is this adventure that encouraged him to begin a career in meteorology first with NOAA and now half-time for NOAA through the Cooperative Institute for Research in Environmental Science at the University of Colorado. He sees this as a chance to launch one more of what could be his last weather balloon in the same environment as he launched his first!!! For those of you who don’t know, BAO stands for the Boulder Atmospheric Observatory. He has been a part of this research facility and its 300m tower located near Boulder, CO since its inception in 1977 and is kiddingly referred to as the grandfather by a number of his much younger colleagues. Dan is also blogging about the cruise at http://ciresblogs.colorado.edu/icebreaker/

Georgia –
I’m a
 PhD student at the Department of Meteorology, Stockholm University. I was born in Athens, Greece, I got my bachelor degree in Physics and master degree in Environmental Science at the National and Kapodistrian University of Athens. I moved to Stockholm two years ago to study the Arctic boundary layer and Arctic clouds. This is my first time in the Arctic and my first time involved in fieldwork! On Oden, I am responsible for the weather station, the temperature and humidity sensors and the sonic anemometer deployed midway up the flux mast. Launching radio soundings twice per day is my favorite task.

John –
I’m a postdoc scientist at Leeds University in the UK, working for Ian Brooks. This is my first time in the Arctic. I’ve previously been south on a hydrographic section from the Falkland Islands to the British Antarctic base Rothera, and I’m pleased to get to visit both ends of the world, though sadly not the poles (unless things on Oden go badly wrong…).

My main responsibility on this cruise is the air-sea flux mast on Oden’s bow, making use of my scientific background in directly measured air-sea fluxes. As a sort of hybrid oceanographer/meteorologist, I also deploy the Waverider buoy when conditions allow, launch the occasional radiosonde and help out Barbara and the others with their various systems.

That’s the met team – I’ve also added one of Dan’s IR camera pictures of us from the team photo shoot (Photo 2). The photos were both taken on the Oden’s helipad in a bitter wind, but I think we’ve managed to make our grimaces look like smiles.

Other blogs from the cruise, for both legs 1 and 2, can be found via the official SWERUS-C3 website: http://swerus-c3.geo.su.se

The meteorology team in infra red!

The meteorology team in infra red!

After five days of open ocean work north of Wrangel Island, the Oden has moved further north to our second work area and we have entered the ice! After the grey and featureless monotony of the Bering Straight, everyone on board was excited when the first ice was spotted, some so much so that they were able to ignore the wind chill (about -20°C; Photo 1).

[Photo 1 caption: Pedro braving the wind to spot the first sea ice on leg 2].

So far we have stayed in loosely spaced ice away from the pack and havent spotted any wildlife. The ice is beautiful, with the passing small bergs and patches having a surprising range of shapes and colours (Photo 2), and the actual breaking of ice by the Oden is noisy and dramatic.

[Photo 2 caption: The author enjoying the view. Photo courtesy of Dan Wolfe].

At night (fairly brief this far north in August) the Oden’s front spotlights shining through falling snow onto approaching sea ice creates a spooky, atmospheric scene (Photo 3).

[Photo 3 caption: Oden moving through sea ice at night].