May 31st, 2016 by Kristina Mojica
So far we have been blessed with calm seas and fair winds. We arrived yesterday at our last station, somewhat rested after a 24 hours transit and ready for the grand finale. Neptune had another plan. Half way through the station the winds picked up very quickly, reaching 50 knots with gusts of 60 and the ocean began to build up. The aerosol team got very excited. For oceanographers, the prospect of completing the station looked gloomy. At 11:00 PM I went to the Alvin hanger, the official gathering spot of the nocturnal NCC (NAAMES Coffee Club). All the ‘regulars’ were there with the coffee mugs and it was clear that there would be no overboard deployment of instruments at night (or the day after) so we just sat for a long time, on a pile of crates (aka the bleacher), watching the waves flooding the stern and admiring the power of the ocean. A visit to the bridge provided even more dramatic views of the developing storm.
The nocturnal NCC
Images from ‘the blow’ experienced on-board the Atlantis. Photo: Lee Karp-Boss (top left), Nils Haentjens (top right and bottom left), : Cleo Davie-Martin
A wave splashing on deck of the RV Atlantis during ‘the blow’. Photo: : Cleo Davie-Martin
Twelve hours later, a fully developed sea with 30 ft. waves. Two of the incubators on the fantail got damaged and other items shifted place or were lost for good. No one is allowed on deck. We are rocking and rolling but everyone is still smiling. Lunch required good motor skills and coordination, eating a hamburger while keeping the plate and cup from flying across the table. The lab spaces that normally hustle and bustle with activity are fairly quit today and people take the opportunity to get much needed sleep, process data, relax and play cards. For our team (and the aerosol group) sampling continues through the inline system (described in an earlier blog), pumping seawater into the lab and measuring optical properties, abundances and species composition of plankton. Tomorrow we will begin our journey back to WHOI. Some high seas are still expected but nothing like what we have experienced today.
Written by Lee Karp-Boss (member of the nocturnal NCC)
May 31st, 2016 by Maria-Jose Viñas
By Walt Meier
May 29, 2016 — This morning, we had our second modeling exercise, led by Ian Eisenman of the University of California, San Diego, where we investigated whether sea ice loss is irreversible – i.e., is there a tipping point for sea ice, a point of no return? In the simple models, like the one we used yesterday, once the sea ice disappears under warming temperatures, the ice does not come back even if temperatures cool back down to where they started. This means the loss is irreversible. However, the ice loss is reversible in more sophistical models such as those used for most future climate projections. So are the simple models missing something essential, or do the more sophisticated models get it wrong?
We examined an in-between Goldilocks model –not too simple, not too complicated– and found that the simpler models do miss important processes, such as the fact that heat diffuses into larger regions. This spreads out and slows down the ice-albedo feedback so that if the temperatures cool, the sea ice will come back.
In the afternoon, my group did an optics exercise out on the ice. This primarily involved measuring albedo of the ice. Albedo is basically the proportion of sunshine that gets reflected by the surface. At its simplest, it can be thought of as the whiteness of the surface. A perfectly white surface reflects all of the sun’s energy and has an albedo of 1 and a perfectly black surface will absorb all of the sun’s energy and has an albedo of 0. Albedo is key for sea ice because the ice has a much higher albedo than the ocean. So as temperature rises, the ice decreases, the albedo drops and more energy is absorbed. This added energy warms things further and you get what is called the sea ice albedo feedback, which amplifies the effects of warming temperatures. But the ice doesn’t need to disappear to have the sea ice albedo feedback. Changes on the ice surface – such as melting and ponding – also reduce the albedo.
Measuring sea ice albedo.
Our goal for the day was to measure albedo along a 100-meter (328-feet) line across the ice. It was our first day here with substantial sunlight; we had blue skies interspersed with clouds. Unfortunately, this was a bad day for albedo: to get good measurements, consistent light is desired. So the intermittent clouds make things difficult. Don told us that normally, if he were in the field in such conditions, he would skip the albedo measurements and drill some thickness holes instead. But we went out and gave it our best effort.
In the evening, we had a visit from two native Inupiat whale hunters, Billy and Joe. They told us how hunting bowhead whales is a fundamental part of their culture. The hunters go out onto the ice to the edge of fast ice (ice attached to the coast) and wait for the whale to surface. When they catch a whale, they bring it up onto the ice and share it with the rest of the community. Sharing is part of the fabric of their society – though the hunters make the kills, they are supported by the entire community. At the end of the whale-hunting season in June, there is a big celebration throughout the town with food, music, and dancing.
Because they use the ice to hunt, the Inupiat have intimate knowledge of the ice cover. They have shared this knowledge with scientists; this provides a valuable complement to our scientific data because they see things that satellites, models, and even scientific field observations don’t. For example, they can sense the softness of the ice, indicating a weaker ice cover. They also provide a long record from their personal observations and oral histories passed down over generations. The hunters mentioned how the fast ice used to extend at least 4 miles from shore, but now it only about half that distance. The ice moves out earlier as well, which affects their seal hunting. Also, there used to be a lot of multiyear ice in the area, but now it is rare.
The Inupiat work with the scientists to better understand the changes in the sea ice and their changes on the community. The scientists also help Inupiat by providing data and scientific guidance. With the changing ice conditions, going out on the ice has become more dangerous for the Inupiat – ice floes can break off without warning, stranding hunters. They now can use the Barrow sea ice radar to see how the ice is moving to get a sense of when and where it is safe to go out onto the ice. It was really interesting to hear the perspective from the local community, an essential source of knowledge that provides a view of sea ice that we scientists don’t get in the field, in our models, or in our satellite data.
May 31st, 2016 by Maria-Jose Viñas
By Walt Meier
The Red Team on sea ice.
May 28, 2016 – This morning we did our first modeling exercise. We started simply, modeling the ice’s thickness as the balance between ice growth and ice melt. Ice grows during the winter and melts during the summer. But from this simple start, a lot can be gleaned. The growth and melt rates are influenced by many factors – the amount of solar energy onto the ice, the amount of energy lost from the surface, the heat from the ocean below. We used a simple model to adjust these parameters to see how the thickness responded. Even such a simple model can demonstrate how the sea ice responds to climate change. For example, just a slightly darker surface (e.g., due to more melt ponds during the summer) results in a thinner ice cover because there is more melt.
Two members of the Red Team holding the electromagnetic induction instrument to measure sea ice thickness.
In the afternoon, my group’s activity for the day was ice thickness measurements, led by Jackie Richter-Menge of the U.S. Army Cold Regions Research and Engineering Laboratory in New Hampshire. There were two methods we were shown how to use – drilling with an ice auger (a boring tool) and measuring thickness directly, as we did the day before, and using an electromagnetic (EM) induction instrument. The EM creates a magnetic field that is differently affected by the ice and water. The modification of the field indicates the thickness of the ice. The EM looks like a long pole with a box about the size of a car battery in the middle. You carry the box with a harness around your shoulder and the poles sticking out to each side. You need to hold the pole parallel relative to the ground. Working with it looks rather like a high-wire walker with a balance pole. Unfortunately, the EM instrument was not working, so we couldn’t collect any data, though we took turns carrying it to get an appreciation of what it’s like to use it. It’s just heavy enough and awkward enough to be a challenge, but when it works, it can provide a nice transect of thickness estimates and it’s quicker and easier than drilling holes.
Two members of the Red team drilling with an ice auger.
Without the EM functioning, we had to rely on the ice auger. This is the most accurate way to measure sea ice thickness…or is it? Drilling a hole and using a tape measure is the most direct way to measure thickness and it is indeed most accurate – but only at that point. The ice is tremendously variable. As we saw during our morphology activity, thick 5 meter (16.4 feet) ice can be right next to first-year ice of 1 meter (3.3 feet) or less thickness. You could drill a hole and make the most accurate measurement possible, but it may be totally unrepresentative of the surrounding ice. This can be addressed to some degree by taking several measurements, but you can only cover so much area during a given expedition. It’s just not possible to cover 25-50 km model and satellite observation grid cells in a reasonable of time.
We set out a 200 meter (656 feet) line, drilling holes every 25 meters (82 feet). We also used a snow probe (a long stick you push down through the snow) to measure snow depth every 5 meters (16.4 feet). Part of the trick of doing these measurements is to make sure the observer doesn’t interfere with the measurement. So you don’t want to be making footprints where you measure, because you compress the ice. We set up the convention of walking on the left and measuring on the right. It sounds simple enough, but if you’re not always mindful of that, it’s easy to step over the line.
With our work finished, we ended the day in the traditional way for the Memorial Day weekend: with a BBQ! We had the traditional meal of hamburgers, hot dogs…and reindeer sausages. Along a number of delicious potluck sides brought over by the other huts, it was a great meal. We relaxed and enjoyed good food and good conversation while recounting our day’s adventures and discussing our research.
May 31st, 2016 by Maria-Jose Viñas
By Walt Meier
Walt Meier on a snowmobile.
May 27, afternoon – After our morning orientation and introduction sessions, I headed out onto the ice for the first time. We were split into four teams; each team will rotate through a different activity every day with each activity being led by one or two experts that will serve as our guide. I was assigned to the Red Team. Our activity for the day was sea ice morphology, or studying the forms of sea ice, and it was led by Chris Polashenski at the U.S. Army Cold Regions Research and Engineering Lab and Andy Mahoney at the University of Alaska, Fairbanks. All the other activities were being conducted within a short walk of the beach, but in order to see different types of ice, we needed to roam farther. This meant using snowmobile. After getting comfortable on the machines, we headed out. Our first stop was on a first-year ice floe, or is ice that has grown since the previous summer. This type of ice is generally thinner than multi-year ice (ice that has survived at least one summer melt season) and its thickness is largely controlled by the air temperature during the winter (though how much snow falls is important too). Colder temperatures mean more ice growth and thicker ice at the end of winter. We measured the thickness by drilling a hole through the ice using an auger. Then we dropped down a measuring tape. The tape has a folding metal bar at the end that catches the ice at the bottom of the hole; the tape is pulled taut and the thickness is read off the tape.
An ice mass balance station in Barrow, AK.
According to Chris and Andy, first-year ice in the area normally should be about 1.5 meters (5 feet) thick. We measured only 0.75 m. That means it’s been a very warm winter around here. But that is nothing new; in recent years, warm winters have become the norm as indicated by thickness measurements. For the past several years, Andy has been installing a sea ice mass balance station on the ice, automatically taking thickness readings every 15 minutes through the winter. The data is available online here.
A polar bear in the distance.
Next we head further north, past Point Barrow, the northernmost land in the U.S., toward the fast ice edge. On the way, we spotted two polar bears in the distance. Polar bears are not an uncommon sight. They usually hang out near the ice edge hunting seals, though they sometimes wander into town, which can be a problem. At this time of year they are attracted by the whale carcasses that the native populations pull onto the ice as part of their traditional whale hunts. The bears were distant and barely visible, but it was quite exciting to see a bear. Polar bears can be dangerous and during all of our activities on the ice, we will have a polar bear spotter –a trained local resident carrying a shotgun – with us at all times.
We left the polar bears to their business and rode further out to a multi-year ice floe that was more than 5 meters (16.4 feet) thick. We attempted to measure the thickness, but we didn’t break through the bottom of the ice at our auger’s (boring tool) maximum 5-meter length. To my untrained eye, the multiyear ice didn’t really look much different than first year. But with careful viewing, one could see an elevation change compared to the first-year ice. It wasn’t a lot, but a just little more elevation on the surface that floats above the ocean translates into much thicker ice because roughly 90 percent of the ice thickness lies beneath the surface of the waters. So a 5-meter thick floe of sea ice rises only about 50 cm (20 inches) above the waterline. The most distinguishing characteristic, at least at this time of year, are the brilliant blue melt ponds that form on the surface. As the snow melts, the melt water will accumulate in depressions in the ice, pooling into ponds. The crystal clear water on top of the pure multi-year ice produces a distinctive turquoise color reminiscent of the water around a tropical island. Melt ponds are very important because they absorb much more solar energy than the surrounding ice, which accelerates the melting process. But to be honest, when seeing a pond in person, the first thought one has is how pretty they are.
Walt, standing on a melt pond.
Just a few meters away, back on first-year ice, was another melt pond. But this had a much darker color due to the thinner and flatter ice. The water was also somewhat salty because first-year ice still retains some salt. The salt gets flushed out of the multiyear ice, so the blue ponds on the multiyear ice are fresh water suitable for drinking. We tried some and it was quite refreshing – ice cold!
Next, we headed over to a large piece of ridged ice. Ice ridges form due to ice floes being piled into each other due to winds or waves. The fast ice does not move, but the drifting ice beyond does and when the winds blow toward the land, the drifting ice collides with the fast ice, forming mountains of ice. The one we investigated was around 5 meters (16.4 feet) high. This means the ice could extend 50 meters (164 feet) deep below the surface. However, the water is fairly shallow off the coast and in reality, the ridge was likely grounded to the sea floor. These grounded ridges actually stabilize the fast ice by acting like big support columns, holding the fast ice in place. This explains why the coastal ice remains in place long after the drifting ice has retreated.
The morphology activity was quite humbling to us satellite data scientists and modelers. We work at scales of 5 to 50 kilometers (3 to 31 mi) – i.e., we’re observing or modeling sea ice in 5-50 km aggregates. Here over just a few kilometers we saw a tremendously varied icescape. Even over just a few meters, we saw multiyear ice, first-year ice with melt ponds on each. How can interpret our satellite data to account for such variability and how can we simulate it the models?
With the ridged ice, we completed our tour of the various forms of ice found in the Barrow area at this time of year. We hopped on our snow machines for the ride home. In front of us the sun broke through the clouds, behind us the polar bears roamed, and all around us, a lovely landscape of ice.
May 30th, 2016 by Kristina Mojica
Today is the last first day of a station, since we reached station five around midnight last night. I think the entire ship was glad to finally have a day to sleep as we traveled yesterday! It was business as usual for the aerosol people though, since we do not have to deploy most of our instruments—they are running 24/7 and collecting air and particles for us. There are many aerosol people looking for specific compounds, including biologically produced chemicals like dimethyl sulfide. In contrast, I am looking for a needle in a haystack. Rather than looking at water vapor clouds, I study ice clouds.
View of the van ‘trailer park’
These are clouds that tend to form higher in the atmosphere where it is colder. These colder temperatures can cause the water vapor to freeze into ice crystals, changing the properties of the clouds. I am interested in the individual ice crystals and when they form. The water vapor normally freezes at very cold temperatures in pure air—around -40 °C. But wait, doesn’t water freeze at 0 °C? The answer is yes, but not if the droplet is small enough, which these are. These small droplets instead get supercooled and freeze at much colder temperatures. If there are particles in the air, sometimes ice can form at warmer temperatures, up to about -5 °C. We call these particles ice nuclei, and they can be anything from pollen to dust to proteins. This is what I am looking for in my samples. We do this by taking ambient samples (samples collected from a tall mast on the bow of the ship) all the time, and while we are on station we take seasweep samples.
The seasweep is a structure that creates bubbles that then burst and create aerosols that are sucked up by a tube that goes to our van and to my filters. As an oceanographer rather than an atmospheric scientist, these are the samples I am most interested in. These samples represent everything the sea could produce as aerosols, and I am hoping these samples have lots of ice nuclei. However, I won’t know what I have collected until I get back to the lab, since my instruments do not travel well. So for now I keep collecting samples.
Above view of a deployed sea sweep.
Written by Elise Wilbourn