A large adult male polar bear, anesthetized and laying on a gray tarp for BIA analysis.

Footprints of the same male. His footprints are side-by-side and consist of two rounded prints topped with short, sharp imprints from his claws. My handprint, small by comparison, is just to the right.

Without food, it is generally thought that animals go through 3 phases of fasting. Phase I occurs directly after a meal, when an animal breaks down carbohydrates from the food for energy. In phase II, hours to days have passed since that meal. The animal begins to burn its body fat for energy, and importantly, the animal mostly avoids breaking down its protein (e.g. its muscles) for energy. Finally, in phase III, the animal runs out of body fat and begins to burn its protein for energy. These three phases are broad categories, and many animals prolong a phase or a transition between phases to survive periods without food. Polar bears in the summer may be in a prolonged phase II – we plan to find out using BIA and other measurements.

Weather has been poor this week. It has been overcast with temperatures mostly in the teens (Fahrenheit), and snowfall and ice fog dramatically reduced visibility. Some days we have not been able to fly at all; other days we launched but flew only several miles before being turned back by low visibility and icing conditions. Our helicopters are only instrumented for flight with visual references (in other words, they do not have the instruments which commercial airliners can rely on in reduced visibility) and there is no point in flying when you cannot see bears. While we wait for better weather I have been able to get other work done – and I have managed to catch the last twenty minutes of “The Incredible Hulk” movie twice, on the television in our living space. The skies began clearing during dinner this evening. Hopefully we will get out tomorrow!

On a recent capture, brief sunshine ended when this bank of clouds and snow followed us home.

This week has been very windy as well. At capture sites, we set up a wind shelter to make sampling easier. Collection bags full of bear breath are visible in the near side of the shelter.

For field work, we have very nice accommodations here in Deadhorse including occasional meals at one of the hotels in town. Polar bears do not have the luxury of eating regularly – sometimes they must go for days or even weeks and months without having the opportunity to kill a seal for food.

Site of a seal kill by polar bears, probably a sow and cub we spotted nearby that afternoon. Seals – here, likely ringed seals (Phoca hispida) – maintain lairs carved out in snow drifts on the sea ice, in which females give birth and nurse their young. The lair is over a hole in the ice, allowing the seals to come and go without being seen. Polar bears seek out lairs and pounce through the snow roof to catch the seals inside – this likely created the hole in the center of the photo. We hovered about fifteen feet above the site for this photo.

Polar bears specialize in hunting seals and seals provide most, if not all, of the polar bear diet. During summer, some bears remain on shore as the sea ice retreats far north; seals are typically not available for hunting on shore during summer, so these bears probably have little to eat. Some bears follow the retreating sea ice north; however, if the sea ice retreats too far north (as has happened in recent years) it moves beyond productive near-shore waters where it is thought that seals congregate. In that situation bears spending the summer on the sea ice may find little to eat as well.

To find out if bears are getting by without food during the summer, we are taking samples indicative of fed status for bears on shore and those on ice. One sample is exhaled breath. Once the bear is anesthetized, we place a mask over its snout; the mask is connected to a two-way valve and the exhaled air fills a collection bag. Usually it takes less than a minute for the bear to fill the bag.

The mask and two-way valve at the right, connected the collection bag at the left.

One analysis estimates how much of the carbon in the exhaled carbon dioxide is actually carbon-thirteen (13C). This is a stable isotope of carbon; unlike a radioactive isotope, it does not readily break down (thus the term “stable” isotope). 13C is slightly heavier than regular carbon and is present in small amounts in most things. The carbon in exhaled carbon dioxide comes from digested food – and, the amount of 13C in carbon dioxide will be slightly different if a polar bear is breaking down its own fat stores for energy than if a polar bear is digesting a seal it has killed. Once our collection bag is full of exhaled breath, we take a small sample of the breath and inject it into an airtight container for stable isotope analysis back at the University of Wyoming.

Another site of a seal kill by a polar bear. Nearby we caught a 940 lb male.

A back paw of the male captured near the seal kill, with a glove for perspective. We had to move quickly to finish this capture and fly back to Deadhorse because a snowstorm moved in and we were losing visibility fast.

PUNTA ARENAS, CHILE– Late last night we arrived at Punta Arenas, Chile. This marks the end of our Iceberg 3 cruise. We have finished analyzing the samples, re-calibrating instruments and we are now ready to start packing. We leave in 4 days; in the interim we will do an inventory of supplies, clean instruments, enter data and pack to be ready to leave on the 19th. Some of us are going back home, others will travel for a few days in the South of Chile or as far north as Ecuador.

Earlier today we met to share our findings during the cruise and plan data analysis and publication of results. Each of us gave a 5 minute (sometimes extending to 15 minute) presentation. It was impressive to see how much we had learned. We have now data that shows the changes in physics, chemistry and biology in the wake of an iceberg, we have improved the comparison of areas affected and not affected by the presence of an iceberg and we can tell how different the iceberg imprint in surface waters is at different times of the year in the North West Weddell Sea (summer, fall and winter). We have accomplished our goal of testing the release of iron to surface waters and the response of phytoplankton and bacteria. This was done not only by measurements in the ocean at different distances from icebergs but also through experiments with iron additions.

These photos show some of the wide variety of icebergs we saw in the northwest Weddell Sea. Notice the blue ice in this iceberg.

The black stripes in this “dirty” iceberg are caused by sediments trapped in the ice.

It was decided we will meet next month in Monterey, California. At that time we expect to have a more in-depth analysis of data that will allow us to synthesize findings in a more comprehensive way. Science carried out in interdisciplinary groups is based not only on results from the individual researchers but also on how well we can combine our findings to describe the iceberg system.

Until the next one!

Nineteen of these subunits are populations of several hundred to several thousand bears; the 20th subunit is the Arctic basin, the area surrounding the geographic North Pole. Bears have been observed almost all the way north to the pole, but it is unknown if any bears are actually residents there. You can see a map of the subunits at this website: http://pbsg.npolar.no/en/status/population-map.html.

Some of the most well-studied polar bears are in western Hudson Bay, where bears come ashore near Churchill, Canada, during the fall months. Bears in the southern Beaufort Sea are also well-studied – this is the subunit of bears on which we are focusing. It is difficult to study what may be the most mobile mammal on earth; in some areas polar bears have home ranges over 500,000 sq km. Because bears move over such a large area and because they travel on variable sea ice, they are difficult to trap. Instead, finding and darting bears from a low-flying helicopter is the most common capture method.

We are using this helicopter this spring as a platform from which to dart bears. The pilot maneuvers the helicopter low and close to the bear, then a gunner leans out the window on the far side and uses a specialized firearm to shoot a dart into the bear. The dart contains a drug that immobilizes the animal and puts them under anesthesia. Here, the helicopter is parked in front of the lab with covers over the engine and the base of the rotors; space heaters beneath the covers keep critical components warm enough to start in the morning.

We are using this helicopter to aid in spotting bears, and to carry personnel and gear. It is smaller than the darting helicopter. The white tank attached to the belly is an extra fuel tank, giving us an additional 30 minutes or so of flight time.

The sea ice at this time of year is very interesting. Almost the entire Arctic Ocean is frozen over, creating vast ice sheets. Ocean currents and wind push these sheets against each other and they break and crumple into jumbled ridges where they meet. This leaves a totally flat landscape punctuated by randomly-strewn ice chunks, some bigger than houses. It is an otherworldly place to fly over, and to walk through.

This is me crouched in front of some ice blocks near our last capture site, on the sea ice about 30 miles north of the coast of Alaska.

We have been down for weather for several days. After working in Kaktovik last weekend, we used a charter plane to haul all of the USGS gear to Deadhorse. We set up all of their base equipment and got out for a capture on Monday afternoon. It was about 0 degrees (Fahrenheit) and mostly sunny. The weather began to turn that night, steadily becoming warmer, windier, and cloudier. Several inches of snow fell yesterday afternoon as well. All of these factors have reduced visibility to the point where we cannot fly. However, the skies are clearing this afternoon, so we hope to get back out today.

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– We are experimenting with iron additions to phytoplankton populations to see possible effects of icebergs as a source of iron. Measuring iron and phytoplankton in the ocean is not sufficient to determine cause and effect. With that purpose, we grow cells under blue light in a freezer van maintained at zero degree Centigrade. We mimic day length (12-hours light) and water temperature (varying from -1 to +0.5 degrees Centigrade). We add iron to some bottles and others are kept without addition, as controls. The cultures are studied for several days, in our case for 2 weeks. This is enough time to determine if iron influences higher growth rate and if final cell concentrations are different among treatments.

Incubations under controlled conditions to study effect of iron addition to phytoplankton.

We are lucky that the phytoplankton growing in our cultures are the same species found most abundant in surface waters. This ensures our results are representative of what occurs in Nature and any manipulation in our experimental design is similar to what the melting of icebergs can introduce to the ocean. Fragilariopsis sp. and Corethron criophilum are the dominant diatoms. They belong to nano- (2-20 micros) and microplankton (>20 microns) respectively. Anything smaller (picoplankton or cells < 2 microns) cannot be analyzed on board and will be studied once at home.

Corethron criophilum in the cultures.

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– Not only do we want to know about what type of phytoplankton grow close to icebergs but we also want to know how well they grow. Primary production, or the rate of inorganic carbon taken up by cells is one of the methods used on this cruise to determine productivity. Diane Chakos takes the water collected by the Niskin bottles in CTD rosette (see previous dispatch) and incubates them for 24 hours under sunlight to estimate daily organic carbon production.

Diane Chakos in the lab preparing samples for a 24-hour incubation under sunlight.

Based on underwater light levels we sample water from surface and at depth corresponding to 50%, 25%, 10%, 5% and 1% of surface light. Within the layer defined by 100% and 1% surface light most of the primary production occurs. Biomass, light intensity and abundance of nutrients, including inorganic carbon, all contribute to production. During austral fall in Antarctic waters we are experiencing only 12-h day light, plenty of nutrients and phytoplankton biomass equivalent to 0.5 milligrams per cubic meter results in about 5-10 milligrams carbon produced per cubic meter per day.

Karie Sines filtering cultures to estimate phytoplankton abundance in productivity experiments by chlorophyll concentration.

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– Within 40 nautical miles southeast of C18A iceberg, we found an area known as the Iceberg Alley: a large concentration of icebergs in western Weddell Sea, moving in a north-northeast direction following the clockwise circulation around the Weddell Sea gyre. Hundreds of icebergs, medium and small, bergy bits and growlers can be seen all the way to the horizon. Our question is: Are phytoplankton here similar to what we found close to the large icebergs? Can we see similar iceberg effect?

An iceberg in the Iceberg Alley.

More icebergs in the Iceberg Alley.

A striped iceberg in the Iceberg Alley.

The number and variety of icebergs is incredible. We sample from surface to 500m with a CTD rosette (Conductivity-Temperature-Depth sensors mounted on a stainless steel frame with twenty-four 8-liter bottles). Phytoplankton concentrate on the surface, where there is plenty of light. Our sampling is designed to see plant abundance and composition and to capture any vertical structure in relation to the chemical and physical properties of surface ocean waters.

CTD rosette: Conductivity-Temperature-Depth sensors mounted on a stainless steel frame with twenty-four 8-liter bottles.

If icebergs change the physical and chemical structure, we expect phytoplankton to show parallel changes. With the release of the micronutrient iron from the ice, do phytoplankton change their concentration? Do we find more large cells, as expected from relief of iron limitation? Or is the mixing of the upper 200 meters pronounced and we see less stratification in the Iceberg Alley when compared to non-iceberg impacted waters? Analysis of cell number, microscopic determination of species and nutrient concentration at different depth will give us answers to these questions? Unfortunately we need to wait until we are back in our home institutions before analysis. The ship motion precludes any detailed analysis under the microscope.

The ARIB Nathaniel B. Palmer’s shadow seen on an iceberg during a clear evening at the Iceberg Alley.

Polar bear tracks in the snow along the Arctic coast in northern Alaska, in October 2008.

Dr. Henry Harlow, Dr. Merav Ben-David, and John Whiteman (left to right) with an adult male polar bear who has been sedated for measurements. They’re sitting in front of a temporary windbreak (to make measurements easier) on sea ice off the northern coast of Alaska in October 2008.

Summer is a critical time for polar bears and climate change is lengthening Arctic summers, which could have a substantial effect on bear populations. However, much of what is known about polar bears comes from studying them out on Arctic sea ice during late winter and spring. During summer, most sea ice retreats far to the north, leaving some bears on shore for several months. Scientists suspect that these bears face difficult conditions on land; temperatures are warm and there’s little to eat. In contrast, some bears follow the retreating ice north, where temperatures are cooler and there may be opportunities to hunt seals.

To find out how polar bears fare in the summer, PhD candidate John Whiteman and his advisors Drs. Henry Harlow and Merav Ben-David are collaborating with scientists from the US Geological Survey and the US Fish and Wildlife Service. They are capturing and examining bears in early summer and attaching GPS-tracking collars, then re-capturing the same bears in late summer and examining them again. Comparing early- and late-summer indicators of body fat, muscle, and diet tells the scientists how well polar bears are faring in summer months. Additionally, they can use this information to forecast how longer Arctic summers may affect polar bear populations.

The “Welcome” sign at the general store in Deadhorse.

Deadhorse sits at the north end of the Dalton Highway, also called “the haul road.” From my understanding, this highway was built as a service road for the Trans-Alaskan Pipeline, which runs from the oilfields of Prudhoe Bay to Valdez where the oil is loaded onto ships. The Dalton Highway parallels the pipeline for much of its long, winding journey. The highway was opened to the public in the 1990s, although it is still mostly gravel and rough driving. The highway begins here in Deadhorse, where I drove past it today on my way to the general store.

North end of the Dalton Highway.

However, we would not be driving to Deadhorse – we have done all of traveling by plane. Alaska Airlines flies to Deadhorse from Anchorage and Fairbanks, and many oil companies have private flights for their workers. The surprising accessibility of Deadhorse – if you are willing to spend days in a capable vehicle or willing to buy an expensive plane ticket – must be due to its role in oil extraction in the Prudhoe Bay oil fields. The town itself feels like a giant construction site. All buildings sit on elevated gravel pads, about eight feet above the tundra. Trucks and heavy machinery are everywhere, and equipment is constantly rumbling.

More accurately, the town feels like a cross between a construction site and a lunar module. Everything is built to withstand the fierce winter weather, with windchills that can fall below -100 Fahrenheit. Most buildings seem to have been built for ease of transport and assembly – many buildings are actually a series of connected, insulated trailers.

Our research team was up here last August for our first season of polar bear captures. We caught almost 30 bears (this includes adults and cubs) for measurements. Some adult bears received a GPS satellite collar as well. We tracked these bears via satellite during September. We returned in October and recaptured as many of these bears as possible, to re-examine them and see how they had changed during the intervening 1-2 months. This spring we are beginning another capture season – our first day of captures, weather permitting, will be Monday, April 20th.