Drilling at Site U1361
Position: 64º 24.6’S, 143º 53.2’E
Water Depth: 3470 meters
11 more days!

ABOARD THE JOIDES RESOLUTION, OFF THE COAST OF WILKES LAND, ANTARCTICA– Hi folks! We’ve been busy the past 9 days. We are coming to the end of our work window here in Antarctic. Summer has ended, the nights are much longer, and next Tuesday we must begin our transit back to Hobart, Australia.

We made our last attempt to get into one of our continental shelf drilling sites but were stopped once more by sea ice. All of the ice here is frozen seawater as opposed to glacial ice.

The sea ice is porous and inside the pores are salty brines that support plant and bacterial life. Here we are trying to collect so ice, but it’s a long way down to the water for this little bucket, especially when working from a moving ship.

We finished drilling deep into the seabed at Site U1359, encountering sediments and rocks that span much of the last 13 million years. For several hundred meters we found layers of rock that alternated between green and brown over distances of 2 to 4 meters. The green parts of the cycle showed evidence of intense mixing of the sediments by animals living at the seafloor while the brown parts showed something quite different – very well-developed laminations that could not have survived if the sediments were mixed. There were different materials in the layers too – some contain more shells of diatoms, the main plant in the surface waters of the ocean. We don’t yet know what these cycles of green and brown represent but we think they reflect the continued glacial-interglacial cycling of the Earth’s climate many millions of years ago.

Today we are in a very cold period in the long-term history of the Earth, and have been for most of the past several million years. Because the Earth is already quite cold, when we have glacial-interglacial cycles, we see large ice sheets coming and going at both poles – in Antarctica, Greenland, and over large parts of North America and Scandinavia. This waxing and waning of polar ice is driven by small changes in the shape of the Earth’s orbit around the sun (it changes from an ellipse to more circular and back again over about 120,000 years), the tilt of the Earth’s axis (it wobbles a bit over 40,000 years), and the exact seasonal timing of when the Earth is at its closest approach to the sun. All of these “orbital” changes impact how much sunlight reaches the Earth as well as when and where it warms the Earth seasonally. Sometimes, the Earth is in an orbital configuration that produces warm winters and cool summers – a combination that usually allows ice sheets to form and grow. Some 10’s of thousands of years later, the opposite occurs – warm summers and cool winters – which can cause ice sheets to rapidly melt. In today’s cold world, these small changes have big effects as the Polar Regions are cold enough to allow large ice sheets to form and last through the warmer periods. Antarctica has been covered in a large ice sheet for many millions of years because of this overall cooling. It still waxes and wanes along its margins but it is always present in the continent’s interior. But prior to about 2.5 million years ago, there was no permanent ice sheet in the north polar regions – it was simply too warm. Further back in time, the Antarctic ice sheet was much smaller than it is today but it was still dancing to the rhythms set by the Earth’s orbit.

What we were seeing at our last drill site and what we are looking for at our latest site is evidence of how these glacial-interglacial cycles affected the Southern Ocean and how they in turn may have been different because the planet was a little bit warmer than today. By studying this we can learn more about how small changes in the planet’s temperature can affect things like ice volume, sea ice extent, and the productivity of the ocean. This is directly relevant to understanding our Greenhouse future. Although all the climate variability that occurred millions of years ago was “natural” (in other words, not caused by people), the strength of the signal that caused these past changes (the orbital changes in this case) is not very different from the strength of the signal we expect from the man-induced increase in carbon dioxide levels in the atmosphere.

The poles are a great place to study both natural and man-induced changes in Earth’s climate because of a phenomenon called polar amplification. We know from many hundreds of studies of the past 50 million years of climate change that whenever the Earth warms up, the poles warm up more than the planet’s average. The converse is true for times of cooling. We don’t yet fully understand the reasons why but based on these studies of the past we shouldn’t be surprised that the poles are warming up very quickly today, at a rate greater than what we see in the tropics or the temperate belts. The cores we collect on this trip have the potential to tell us more about when and why polar amplification occurs.

I’ll send one more blog from this trip once we have cleared our last hole and are heading for Hobart. Sixty days is a long time to be as sea and working every day for 14 hours or more. We are all excited to get home.

I had a chance to get off the JOIDES Resolution a couple of days ago when we were running a “man overboard” drill. We recovered the dummy and then I was able to take these shots. It was our warmest, sunniest, calmest day by far. You’d never know we were in Antarctic waters.

We’ve been seeing lots of whales at our continental rise sites. The whales come to Antarctic waters in summer because of the abundance of food.

At dawn one day, we had more than 35 Humpback whales around the ship. From a distance you usually first see their spout, which you can make out here.

More storms and more icebergs. This seems to be the story around here now. Once each week we get a major blow and the seas kick up.

Then when we are near the continental shelf we see more icebergs…..

The bone lander after recovering it on the back deck of the ship. The attached whale bones will be removed and analyzed by Dr. Craig Smith and colleagues to see what animals, big and small, have made these bones their home.

While the deep sea below the euphotic zone (the top 100 or so meters, or 300 ft, where light penetrates and primary production from algae occurs) was long thought as a vast oceanic desert where few organisms (even microbes) could survive, research in the last century starting with the Challenger Expedition between 1872-1876 has shown a rich diversity of marine life specialized to face the harsh conditions of high pressure, cold temperature, and complete darkness. One of these, the annelid worm Osedax, has developed the ability to feed on complex hydrocarbons in whale bones, using bacterial endosymbionts (bacteria living inside the worms) to break down the compounds inside the bones into a usable form of energy.

Our ship, the Palmer, breaking through sea ice in the Weddell Sea.

As luck or fate would have it, the sea ice around Antarctica seems to be unusually persistent this year, reaching far beyond its usual summer extent, which makes moving forward a slow going process. For those of you living in cold regions of the United States and the world, you might be used to seeing your lakes and rivers freeze and thaw as the seasons progress. Sea ice around the Antarctic goes through much of the same cycle, building during the winter (between April and September in the Southern Hemisphere) and melting during the summer. The extent of ice any given year is related to weather as well as global climate, and has been shown to decrease around the Antarctic Peninsula over the past 60 years.

Sea ice extent in September (austral winter) of 2009 as measured by satellite. Black corresponds to land, blue to open water, and the other colors to sea ice. The approximate location of the Larsen B ice shelf, our target, is indicated by a white circle. Notice the band of purple surrounding that location, indicating persistent sea ice.

Sea ice extent in December (summer) of 2009 as measured by satellite.

Here’s another view of the same data. In this version, grey corresponds to land, blue to open water, and white to sea ice. The approximate location of the Larsen B ice shelf, our target, is indicated by a black circle.

Sea ice extent in December (summer) of 2009 as measured by satellite.

Because the Antarctic serves as home to a rich assemblage of species, including fish, seals, sea birds, whales, and penguins, you can imagine that life doesn’t simply stop in the cold polar winter… it adapts. Algae, which you may think as growing only in bodies of water such as lakes, oceans, and rivers, can also grow on the underside and inside of sea ice. If you look at the picture of our ship’s track you’ll notice a surprising brown color to the normally white or bluish ice. This color is due to ice algae, which due to their adaptation to low light conditions thrive both in the summer and winter. Ice algae may play an important role in starting the phytoplankton blooms that are common in the ocean as the ice retreats in the spring. Because it grows in such great abundance it also provides an important source of food to higher trophic levels, include the krill that whales love to eat. So in a way, what happens on the often hidden underside of ice can have a great impact on the bigger Antarctic animals we all know and love!

Cracks in the sea ice expose algae growing underneath and inside the ice.

The three types of killer whales. From R. Pitman, P. Ensor, J. Cetacean Res Manage 5(2):2003.

Ross Sea killer whales appear in the McMurdo Sound area and the southern Ross Sea, in early December and ply various fast ice edges (ice attached to the land), which as the season progresses recede further and further south toward the continent. They also apparently forage under or along the edge of the Ross Ice Shelf by Cape Crozier on the other side of Ross Island. These whales feed on fish that live under the fast ice and as the ice recedes the whales are able to exploit more and more feeding territory. Sightings of these whales, from land, helicopters and ships have been carried out through the years, most recently from the Cape Crozier and Cape Royds penguin colonies on Ross Island, where it has been noticed that the presence of whales (including minke whales) follows a shift in the diet of the penguins.

Killer whales foraging in a sea ice crack.

In 2005 the ratio of C to B killer whales was 50-1, but over the next few years it steadily dropped to 16-1 by 2008. As the observed numbers of B whales (seal eaters) did not change during this time, the altered ratio was due to the decrease in Ross Sea killer whales. During the years of these observations another important series of events was taking place.

Although commercial fishing of the Antarctic toothfish (sold as “Chilean sea bass”) in the Ross Sea began in 1996, it was expanded in 2004 from 9 to 22 fishing vessels; not surprisingly that same year the catch reached its allowed limit of 3500 tones. These boats target the largest adult toothfish, which is the same size those taken by the whales. Toothfish are a slow growing species which do not reach maturity until 16 years old. Many of these fish taken in the fishery were over 25 years old, some older.

Antarctic toothfish.

Since 2004, the commercial catch has remained steady year by year. Catch and release efforts of toothfish by scientists in McMurdo Sound remained steady from the years 1974 to 2000, but dropped 50% in 2001 a few years after the commercial fishing began and then to 4% in 2007, only 3 years after the peak commercial catches began. It would appear that the drop in Ross Sea killer whale numbers is related to the increase in the commercial fishing of the toothfish.

Are there any other animals that would be affected by the reduction in toothfish numbers?

Weddell seals also take toothfish as a primary food source and their numbers have not decreased in McMurdo Sound, though trends elsewhere along Victoria Land are unknown. Seals are able to dive deeper and stay under longer than the whales and therefore able to catch the fish which are safe from the whales. Seals therefore not only forage where the whales forage, but also in areas the whales can not reach, places covered with extensive fast ice where small cracks provide breathing holes. Seals also eat silverfish. It is thought that whales also eat silverfish but there are no confirmed sightings for this. The whales therefore may be more sensitive to changes in toothfish availability. If the toothfish industry continues to extract the current yearly numbers, it is predicted these creatures will decline more rapidly.

For more information about the Ross Sea, the toothfish industry and how it is affecting penguins, whales and seals go to The Last Ocean.

The hut which is my home away from home for several days in Barrow.

Inside, the curve of the walls stands out. I am enjoying the last couple days on shore before heading to the ship.

This morning we woke to a thick dusting of snow which did not melt as the day warmed. We are staying at the facilities of the Barrow Arctic Science Consortium, or BASC, which is a kind of clearinghouse for many research projects that are based in this area. The area also houses the North Slope Borough Department of Wildlife, and I?isa?vik College.

This bowhead whale skull stands in front of the college. Subsistence hunting of bowhead whales continues to be an important cultural feature of this area. The autumn hunt begins tomorrow here in Barrow – perhaps over 30 people will launch in small boats from the beach outside of town in the morning, seeking to find and land a bowhead whale.

Our study is the lead project on the science portion of the cruise on the US Coast Guard Polar Sea which begins tomorrow. Several other projects and a total of 24 personnel are involved in the science portion, and in the last three days, everyone has arrived in Barrow and found temporary accommodations. Tomorrow morning I will get up early and walk over to a small warehouse with a large load scale, and, hopefully, beginning at about 715am, each person will come by and we can count, weigh, and label their baggage. Two helicopters and one small boat will be used to ferry people and luggage to the icebreaker, which is planned to be anchored several miles offshore to the west. Simultaneously, 32 people and all of their luggage will be disembarked from the ship. After several meetings and rounds of organization today, the schedule seems to be on track.

We heard that sound again two days ago at Cape Royds, having heard it before in January 2005, when a several square kilometer opening appeared in the fast ice just offshore in a matter of hours. The ice was dissolving, or would we call it melting?, and it was happening so fast that you could see it disappearing without even needing your imagination to be going overtime. It’s kind of like putting an ice cube in a cup of boiling tea water to watch it disappear; only here the water is just a degree above freezing. That’s plenty warm as ice goes. In 2005 the fast ice was thinner, so it went from white ice to blue water; this year it was much thicker, so for a couple of weeks it slowly turned darker shades of gray, as it took on more water. Then, fzzzzzzz.

Otherwise, except for this new patch of open water within the ice, called a polynya (a Russian word; without a doubt the Inuits have a name for this, too), there is still fast ice to the horizon as I have described in various of my previous dispatches.

The Swedish icebreaker Oden going south, very slowly, through the ice a few kilometers out in McMurdo Sound, while a polynya begins to form next to Cape Royds.

The south ‘shore’ of the polynya, the day after it initially formed, showing proximity to the Cape Royds penguin colony (tan area on left side of image). The polynya is to the right, beginning to dissolve the gray ice in the center of the image.

In fact, in the Arctic, Inuit villages — and, for that matter, seabird colonies — are located near to polynyas. And, wouldn’t you know, so are penguin colonies, although at the opposite end of the Earth. This is because polynyas allow these predators much easier access to their food. Normally, McMurdo Sound is one big polynya, and the penguins are here at Royds because of it. As I’ve been making the point in previous dispatches, the Royds penguins have been having a hard time of it this season, because their polynya didn’t form, owing to calm winds which allowed the ice to thicken until not even the strongest winds could blow it away. So, they’ve had a very long walk to get food. That is, up until a few weeks ago, when the few remaining penguins still having chicks were provided a large crack to feed in, just 4-5 km north of the colony. Now they’ve got a full-fledged, mini-polynya and all is right in the World!

Well, just like in 2005, within a day of the polynya forming, a couple of minke whales showed up in it! Where they came from, I’m not sure, but they may have followed the Oden into the ice (35 km from the fast ice edge), and then pealed off when a crack that intersected the icebreaker channel allowed them to get to the Cape Royds polynya. Maybe they heard it fizzing! Or the sounds of joyful penguins!

The minke whales, for several hours, cruised around the polynya feeding all the time. They’d submerge for 6-8 min at a time and likely were like big “Hoovers”, i.e. vacuum cleaners. Between dives, they exhaled (i.e. whale “blows”) 4-5 times, clearly audible in the still air from a kilometer away. Within a couple of hours after the whales’ arrival, the penguins’ diet switched from krill to fish. I’d been monitoring it by watching what passes between adult and chick everyday for the past few weeks. Wow! I knew that the whales could do this to the penguins, but I didn’t realize that the whales were so efficient! Not long after the whales left (they’ve not been seen for about 24 hours now) the penguins’ diet switched back to krill. Therefore, this is pretty good evidence for what we call “interference competition”. The whales certainly eat a lot but also their vacuuming causes the krill to try to escape, of course. And what krill do when being pursued, if they can, is to dive deeper and, it seems, deeper than penguins want to go, especially when there are enough fish to be had at shallower depths, though apparently not in a density that in this case would interest a minke looking for easy pickings. If the whales had vacuumed all the krill, when they left, there would be no food for the penguins. As it was, the krill ventured back up into the light (where the phytoplankton occurs that the krill eat), to then be caught by the penguins again. Both whales and penguins go for the easy meal, i.e. that nearest the surface.

Parent feeding its chick. With binoculars, if you get the right angle, usually it is possible to determine whether krill (pink) or fish (gray) is being fed to the chick.

Well, so, you’d think that maybe whales are an annoyance to Adélie penguins. As it turns out, though, minke whales are life savers! Adélie penguins, if given a choice, would always want to have minke whales around, despite the whales’ appetite and despite the best (?) efforts of the Japanese whalers. You see, minke whales — because, like Adélie penguins, they are pack ice denizens — have evolved a very long and sharp “beak”. When you see the whales in areas were the sea is freezing, it becomes quickly obvious why this is a good thing. The whales use their rostrum to break breathing holes in the new ice.

This ice is thick enough that penguins walk over it. With the whales around, though, the penguins can swim between whale breathing holes much faster than walking. In fact, several years ago, when on an icebreaker at the time of ice freeze-up in the Amundsen Sea, one day there were whales and penguins swimming around, and then the next day, with a dramatic drop in temperature and a freeze, there were whale holes but no whales or penguins. Together, they had escaped north far enough to move away from the area of freezing.

A minke whale pushing up through recently frozen sea ice, the ice around it being 4-5 cm thick.

All but one of these penguins found a hole left by a minke whale; the next whale breathing hole is just behind the lone penguin and this flock of penguins is next going to appear in that hole.

These penguins are not walking on frosted glass. They are walking on ice thick enough to support their weight, but not thick enough that a minke whale could not break a hole.

It is good for Adélie penguins to have as many minke whales around as possible. This one, like the pied piper, is making a “channel” through new ice, soon to be followed by a flock (school?) of penguins, who would much rather swim than walk.

Penguins need whales, especially minke whales, as friends.

Antarctic krill, Euphausia superba, is the largest krill species.

Adélie penguin nesting areas on Avian Island, stained red due to the penguins’ highly krill-based diet.

Dip a net into coastal Antarctic waters and you’re likely to pull up more than a few pinky-sized shrimplike crustaceans. These are krill, and if they look like small-time players in the game of life, it only goes to show exactly how deceiving looks can be.

The Antarctic food web is the simplest on the planet, and krill are at its hub. An estimated 500 million tons of krill live in the Southern Ocean, making this the most abundant animal in the entire world. Krill are such a universal food in Antarctica that for almost every animal that lives here, a “three degrees of krill” rule applies: You are krill, or you eat krill, or your food eats krill.

Whales, seals, penguins, albatross, petrels, fish, squid—every animal species living in Antarctica depends directly or indirectly on krill for survival. This heavy reliance on a single species makes the Antarctic ecosystem an unusually fragile one, particularly since many animals—including baleen whales such as the humpback, fin, minke, and blue whales—eat krill almost exclusively.

Krill, in turn, filter-feed on the abundant phytoplankton in the open ocean. In winter, they also gorge themselves on the ice algae that grow on the underside of the pack ice. A single krill can scrape clear the algae from a square-foot (.09 m²) patch of ice in ten minutes, zigging and zagging back and forth lawn mower–style.

Corethron, a type of phytoplankton, highly magnified under the microscope.

This image, taken by a remote operated underwater vehicle (or ROV), shows how most krill feed by swimming upside-down directly under the ice, grazing as they go.

Extra cold winters are a boon to most animals living in Antarctica. Colder winters mean more pack ice, and more ice algae to feed more krill, which means more food for all. In warmer years, when the pack ice is reduced, there’s a measurable decline in the krill population, sending shock waves of scarcity through the shallow Antarctic food web.

Even in good years, competition for krill can get fierce. Biologist David Ainley discovered that minke whales drive Adélie penguins from the best krill feeding zones, forcing the penguins to venture farther afield or switch to hunting fish. Humans have also joined the fray, using nets to harvest roughly 100 million tons of krill each year for use in animal feed, dietary supplements, as fish bait, and also for direct human consumption.

Researchers fear that global warming and dwindling pack ice are likely to pose serious challenges for the Antarctic ecosystem. In the short term, however, there is one perk to warmer temperatures: an increased number of icebergs. Marine scientist Maria Vernet has found that these floating oases deliver nutrients to the surrounding water as they melt, creating flourishing (if temporary) mobile ecosystems on and around the bergs.

Drawn to the cold, nutrient-rich Antarctic waters, ten species of whales spend their summers at the bottom of the world. Often sighted by research scientists are the humpback, minke, and orca.

Humpback whales in the “singing position.”

A playful humpback breaches near a Long-Term Ecological Research (LTER) ship.

A humpback fluke slapping near Palmer Station, Antarctica.

Humpbacks
Humpbacks are best known for their haunting songs—a sequence of squeaks, roars, moans, and whistles that, analysts say, contain rhyme, rhythm, and other elements found in human music. A song can last about twenty minutes (and may be repeated for hours), reaching an audience as far as twenty miles (32 km) away. It’s generally believed that only the males sing, and it appears that they sing primarily in their breeding grounds, so an early assumption was that these are songs of courtship. But further research showed that males, not females, are attracted to the singer, which calls the courtship idea into question.

All the whales in a particular population sing the same song, which evolves over time: Certain parts of the previous year’s song are omitted while new parts are added. This pattern of change has led some people to speculate that the songs are a form of oral history—an appealing idea, but one that seems impossible to prove or disprove. It’s likely we may never know the meaning of their captivating music.

Humpback song, courtesy of NOAA.

If being the opera stars of the ocean wasn’t enough claim to fame, humpbacks are also accomplished acrobats. They can propel their 50-foot-long (15 m) bodies out of the water (called breaching), sometimes twirling around before falling back into the sea with a loud crash. They can lift about a third of their body vertically out of the water (spyhopping) to take a look around. They may also slap their tail repeatedly on the water (lobtailing or fluke slapping), or slap the water with a fin. The reasons for these behaviors aren’t known, but observers find them enchanting. As marine science graduate student Cassandra Brooks wrote in a dispatch from Antarctica in February 2008:

Humpbacks are especially curious whales, and some encounters are amazing. Two years ago we had a pair of humpbacks that seemed just as delighted in us as we were in them. The whales spy-hopped, breached, rolled and fluked within only a few meters of the boat, and we dashed from port to starboard side and back again to follow every move.

Another distinctive humpback behavior is bubble-net feeding, a cooperative hunting strategy that involves creating a “fishing net” out of bubbles. The whales form a circle up to 100 feet (30 m) wide below a group of prey, usually krill or a school of small fish, and then blow a cylindrical wall of bubbles that encloses the prey. Then they swim up through the net to the surface, gulping rich mouthfuls of food. Humpbacks are baleen whales, named for the hundreds of flexible plates, called baleen, that are attached to their upper jaws. The plates are filters that trap the whales’ prey. The more densely the prey are concentrated, the better it is for the whales, so it’s good, from the whales’ point of view, that the prey won’t attempt to swim through the bubbles.

A minke whale surfaces in the Ross Sea, Antarctica.

Minkes
Although smaller, minkes are closely related to humpbacks. Both belong to the rorqual family of whales, also known as the “great whales,” all of which have a large number of pleats along their throats that expand while they’re feeding. There are at least two species of minkes: the common, or northern, minke and the Antarctic minke, with the dwarf minke considered a possible third. There are also several subspecies.

Minkes make a number of sounds, including clicks, grunts, thumps, and the interesting “boing” that was just identified as a minke vocalization in 2002. The sounds can vary from population to population and are helpful to researchers who study these animals.

The minke whale boing sound, courtesy of NOAA.

As acrobats, minkes are pretty much up to snuff. In the Antarctic summer, they’re seen spyhopping in the open pack ice, and they’re often observed breaching. Like their humpback cousins, minkes are curious, and they’ll often swim up to a ship to see what’s going on.

After a summer in the Antarctic, many minkes migrate to warmer northern waters to mate or to give birth to calves conceived the previous year. But some have been spotted in the middle of the winter pack ice where they apparently spend the season. Like other rorquals, they have rather pointed heads, which they stick up through narrow cracks in the ice to breathe.

Orcas amid the Antarctic pack ice.

An orca swims through a leed in the Antarctic sea ice.

Orcas swimming together in McMurdo Sound.

An orca skyhops next to the U.S. Coast Guard icebreaker Polar Sea, with Mt. Erebus in the background.

Orcas
On display at marine parks throughout the world, and often the object of whale-watching expeditions, the beautiful black-and-white orca is one of the best-known cetaceans. It’s also called the killer whale—a name that may be derived from “whale killer” or “killer of whales” because some orcas hunt baleen whales. Orcas belong to the dolphin family, Delphinidae, and like other dolphins they have strong, sharp teeth that they use in hunting.

Highly social, orcas are generally found in pods, groups typically containing from a few to fifty individuals. It’s thought that they talk to each other primarily with whistles, squeaks, and squawks. They also produce click sounds that mostly, it’s believed, help them know what’s going on in the neighborhood. The clicks are reflected back from objects so the whales can be aware of, say, an iceberg that should be avoided or perhaps some seals that would make a tasty breakfast.

Orcas are found in all the world’s oceans, but they’re most abundant in Antarctica. It’s believed that they tend to move northward in the winter, but they don’t have set migratory routes, and orcas have occasionally been seen amid the pack ice in midwinter.

Three distinct groups of orcas, known as ecotypes A, B, and C, have been observed in Antarctic waters. They’re distinguished from one another by differences in size, coloring, and dietary preferences.

Type A orcas go after the really big prey, primarily minkes, but larger baleen whales as well. Male type A orcas may grow to about 32 feet (10 m), about the same size as a minke but smaller than humpbacks and significantly smaller than the blue whale, the largest of them all at over 80 feet (25 m). The orcas’ strategy is to hunt in packs, which has earned them the nickname “wolves of the sea.”

Type B orcas fancy seals and penguins, while type C orcas dine mostly on fish. Interestingly, this puts penguins in danger of predation from type B orcas—and puts them, especially the Adélie penguins, in competition with the minkes for krill and in competition with the type C orcas for fish. As penguin researcher David Ainley noted in his dispatch from November 2007:

When the minke whales arrive in larger numbers, and the type-C killer whales, too, we can expect the penguins to have more difficulty finding food. These whales go after the same food as the penguins, and take much more of it in one gulp!

A 1790 engraving depicting Captain James Cook’s whaling party.

Past and Present
Humpbacks were hunted mercilessly, but they’re slowly recovering. Still, the population is estimated at only about 30,000 worldwide.

The minke population in the Southern Hemisphere seems healthy right now, with perhaps a million animals. Because of their relatively small size, about 32 feet (10 m) in length, they were ignored during the height of commercial whaling. And the decline of other baleen whale species due to hunting left more food for them. They’re hunted today, though: Japan issues scientific permits for killing several hundred Antarctic minkes every year. Many people think that this is simply a way to circumvent the moratorium on commercial whaling that’s been in place since 1985-86. And many scientists find it particularly disturbing when whaling (or fishing) is conducted in the Ross Sea, which is one of the last truly functional marine ecosystems in the world.

Orcas, like the minkes, escaped the horrors of commercial whaling. Their numbers in the Antarctic are thought to be about 70,000. But as top predators, orcas are particularly affected by chemical contaminants such as PCBs, and some people feel that live capture by marine parks and other institutions also harms the species.

Future
All these whales may face a serious threat if global warming causes a significant loss of sea ice. If that happens, it’s anticipated that the shrimplike krill will be in short supply—and at a time when krill are being caught in increasing numbers by commercial fisheries. This will be bad news for the humpbacks and minkes, as well as penguins, seals, and other predators that compete for these nourishing little morsels. And indirectly this will affect the orcas as well.

Placing a Mooring

Kate’s moorings, like most others, are constructed to be placed on the sea floor at a particular location and depth. Locating nearly anything on the surface of the Earth has become much easier with the widespread use of the Global Positioning System (GPS) and its relatives (assisted GPS, differential GPS, carrier-phase GPS, Real-Time Kinematic (RTK) GPS, etc). Knowing the depth (and associated bottom contours) at a point in the ocean is less straightforward, yet these details are important for designing and manufacturing moorings, as these details affect certain aspects of a mooring’s design such as the amount and strength of cable required, the weight of the anchor to be used, the amount of buoyance required, etc.

Ocean depths are typically measured with an echosounder (see below) and then recorded on bathymetric maps. Contour lines of the same depth are called isobaths. The map below indicates our ship’s cruise track, mooring deployment/recovery locations, geopolitical data, plus a number of isobaths (black lines) and bathymetric data (salmon-colored tracks).

Cruise track, made available to the science party underway, had a number of optional overlays. This shows the track, geopolitical map, bathymetric data, and mooring deployments/recoveries.

The bathymetric data used to create such maps are measured using either airborne platforms (e.g. satellites) or ships’ sonar systems. Healy has a multibeam sonar system. Using multiple sound beams allows the ship to map out more sea floor information per unit time than would a single beam.

In Healy’s multibeam, sound is emitted through hull-mounted projectors in the form of short acoustic “pings” (which sound a bit like bird chirps when you are on one of the lower decks– bring earplugs if you have to sleep there!). The pings are 12KHz acoustic waveforms that bounce off the sea floor and are picked up by an array of hydrophones (also mounted on the hull). The amount of time between when a ping is sent and when it is received gives an estimate of how long it takes sound to travel to the bottom and back. If the speed of sound in sea water is assumed to be 1500m/s, then the depth (in meters) can be estimated as (1500)(t)/2, where t is the time (in seconds) between the sending and receiving of the ping. However, this calculation really isn’t good enough. The reason is because the speed of sound in water varies based on a number of factors, including temperature, salinity and depth. So, data collected from onboard instruments: an expendable probe (see XBT, below), a CTD that is repeatedly cast into the water (see my previous dispatch that describes the CTD), and archived data, are used to form a sound speed profile which is then used as input to the ship’s SeaBeam 2112 control computer to make corrections to the simple formula above. Using all this information, while also taking into account motion of the ship itself when estimating the time between sent and received pings, the computer can form an accurate bottom map that is made available to anyone on the ship and also shared with others back on shore through one of the various archives at LDEO.

WHOI Mooring Ops. Engineering and Field Support Group logo.

As you can probably see, there is a considerable amount of subtlety in how this works inside the computer. For example, the ship may be experiencing rolling, pitching, or yawing. Movements such as these (especially roll and pitch changes) affect how the beams are reflected back to the hydrophones, and all this must be considered when creating an estimate of far away the bottom is and what features it has. In addition, the temperature of the water varies as a function of depth and can change over time. To determine the temperature/depth relationship at a moment in time, a device called an expendable bathythermograph (XBT) and/or a CTD (described last in my dispatch) is used (e.g., once daily or when the ship moves into an area with different ocean characteristics) to measure the temperature/salinity/depth profile.

An expendable bathythermograph sitting on its launcher.

An XBT looks like a small rocket that is launched by a fixed or hand-held launcher off the ship; the ship can be still or moving. The XBT itself remains attached to the launcher by means of a very fine 2-conductor copper wire that unspools as the XBT descends toward the sea floor. As it descends, it measures temperature while its depth is estimated using an assumed falling rate. The resulting information is displayed to the user and used in forming the sound speed profile for the multibeam echosounder (and for a few other things). To learn more about the finer points of estimating sound speed in water, this link provides a number of more detailed references as a starting point.

Moorings can be used for a variety of purposes, but for this cruise moorings are being used to keep acoustic and oceanographic sensors in place for some period of time (typically a year). Scientist Kate Stafford from the University of Washington’s Applied Physics Lab (APL) has a set of acoustic sensors forming a ‘hydrophone array’ that are to be recovered and (re) deployed later in the cruise.

Hydrophones are passive measuring devices– they do not emit any sound themselves, but instead convert acoustical energy in the water to an electrical signal. Kate analyzes the sounds or “vocalizations” of whales, bowhead and beluga whales in particular, using these instruments. Fixing a hydrophone array in place underwater for a relatively long period of time (a year) allows scientists to listen for the presence of cetaceans (whales, dolphins, and porpoises) from multiple locations, even in poor weather conditions.

Kate pictured with a large mooring float.

Detection Using Passive Hydrophone Arrays

Each hydrophone Kate uses sits inside an instrument that includes the hydrophone itself, a data recorder where the digitized audio samples are stored for later retrieval, and a pack of batteries to keep the whole instrument running for a year or more. These are the instruments that are attached to moorings that are deployed out at sea until they are recovered. When these types of instruments are placed sufficiently close together, more than one will pick up the same vocalizations or sound. When this happens it may be possible to locate and track a particular sound source (animal or otherwise) over time. When the instruments are used together in this way, they behave as an array, or group that is acting together cooperatively. Hydrophone arrays can also be used in estimating animal populations, although gaining high confidence using this approach is an ongoing challenge.

The hydrophone instrument.

When the data from Kate’s instruments is recovered, it can be processed in a number of ways. One way is to simply listen to the sounds on the recordings. A person with enough expertise in doing this can pick out some of the vocalizations and other sounds. As an example, you can listen to the recording of a beluga:

Beluga Whale Recording

A more quantitative approach involves taking the data and analyzing the frequency, timing and intensity (loudness) of particular sounds. A popular way of doing this is to visualize this information on a special kind of graph called a spectrogram. In this spectrogram of a beluga vocalization in the Beaufort sea, for example, the intensity of sound at a particular frequency at a particular time is indicated by the color (blue less intense; red most intense).

Spectrogram of beluga soundings in the Beaufort Sea.

By looking at the spectrogram or other types of graphs (or by using a computer program to do so), acoustic frequency patterns resulting from cetacean vocalizations (or boats, or the sounds of airguns used in seismic exploration, etc.) can be found.

For the interested reader, the analysis of hydrophone data is similar to both signal processing and image processing techniques. Common techniques include matched filters, band-limited energy summation and classification, image matching techniques on the spectrogram or time series, and other frequency-domain analysis techniques such as wavelet-based decomposition. A more detailed explanation of how this can be accomplished and why fixed passive arrays are useful for monitoring cetaceans is given in this paper.

The ultimate goal for much of the related science here is to estimate animal populations, which is important for both ecological understanding and policy-setting reasons. As suggested above, there are a number of factors posing challenges to doing this effectively using acoustic arrays. Animals may use different vocalizations at different points in time and these may vary in many ways (e.g., frequency, phase, amplitude, modulation, etc) based on its activity (e.g., feeding or seeking a mate). In addition, instruments are only capable of detecting a signal up to some distance (which depends on frequency), so forms of statistical inference must be employed in an attempt to estimate a population given a number of detections.

Necessarily, these are only estimates, but they are estimates based on measured data, and moored acoustic arrays offer some significant advantages for making such measurements versus the alternatives of visual observation from ships (or other platforms like airplanes, etc) or from towed hydrophones that only last a few days or weeks. Moorings last a long time and are relatively immune to poor weather so they can offer a richer data set on which to base estimates. Of course, they need to be designed, deployed, and recovered, which generally involves a ship such as HEALY…

Cruise track for HEALY Arctic West Summer Cruise 2008, Leg 4.

The principal work of the first evening included the project of Kate Stafford from the University of Washington, who is retrieving and redeploying moorings placed on the seafloor which are equipped with hydrophones to listen for the sounds of various marine mammals, including seals, walrus, and beluga whales, but with particular emphasis on recording the sounds of bowhead whales (Balaena mysticetus), the sounds of which can be heard at: http://www.dosits.org/gallery/marinemm/15.htm.

The bowhead whales are one of the key marine species in the ecosystem, and important for traditional Inuit culture — their meat and blubber a source of food, and their bones used as sled runners and in house construction. Their baleen (the horny plates in their mouths with which they filter the small shrimp-like euphausiids and copepods — their main food), as shown in the baleen model boat in Day One’s blog, was put to many traditional uses in Inuit culture: as a tough cordage for seal and fish nets; for short lanyards and lashings on sleds; as the tip of dogsled whips; for hunting snares for birds and rabbits; bent into boxes for keeping harpoon heads; made into traditional Inuit snow goggles to prevent snow blindness from glare off snow and ice; as a brow on hats for kayakers to keep spray out of their eyes; as fletching on spears and arrows instead of feathers; and as large knives for cutting ice for igloos, and smaller story knives used to tell stories by ‘drawing’ in snow or dirt. Baleen was also woven together without being cut to form racks hung from the ceiling for general storage, and as floorboards in the traditional semi-subterranean Inuit houses shown in the Day One blogs: a sort of Inuit linoleum! And, in earlier times when warfare between native groups existed, it was also used as plates woven together in the construction of armor. Making of woven baleen baskets was an innovation of the late nineteenth century begun by Barrow resident Charlie Brower.

The bowhead whale is still the principal whale hunted off Barrow. Getting an accurate count of bowhead whales has been a key issue for scientists and the Inuit people for many decades to ensure their proper management and conservation. Preliminary information on the results of the annual aerial survey, along pictures of bowhead whales may be found at: http://www.afsc.noaa.gov/nmml/cetacean/bwasp/index.php. Kate’s hydrophone arrays are deployed offshore of the 100 meter depth line at two locations along the coast in groups of three to allow tracking of whales passing along the coast. Their batteries allow them to operate for a year. In the first day of science, the arrays already deployed from the previous year are retrieved by positioning the ship over their location and generating a specific series of tones which activates an acoustic release. Floats which had remained submerged with the hydrophones are then released from their bottom weights, and the hydrophone and floats drift up to the surface where they are located by a small boat, and passed off to the ship, which then hoists them back onto the deck.

Coast Guard small boat used to retrieve moorings by snagging their floats after release from seafloor.

Once the hydrophones are retrieved, Kate downloads the data from the past year collected by the hydrophones, changes out the batteries and data recording computer hard drives, and later in the cruise will redeploy them. Of concern when retrieving the hydrophones is the ability to find them if there is heavy ice. High resolution (100 meter) satellite images have been requested by the ship showing where the ice is located.

100 meter resolution Radarsat satellite image showing ice concentrations in Beaufort Sea off Barrow, Alaska.

This imagery is from a Radarsat satellite, which is particularly useful as it can see through the ubiquitous fog. In areas where ice concentrations are heavy, hydrophone retrieval can be delayed until the ice has moved away, and the likelihood of retrieving the moorings is more certain: better to wait a bit for conditions to improve than risk a full year’s data.

The principal components of hydrophone mooring array, shown in the photo below being disconnected from the cable by Kate Stafford of the University of Washington and John Kemp of the Woods Hole Oceanographic Institution, are the hydrophone and acoustic release. When the mooring array is redeployed, a float is put over the side first. It is the float which provides the lift to allow the hydrophone and acoustic release to surface, be located by a small boat and retrieved. After the float goes over the side, the hydrophone, and then acoustic release go over, and last of all the weight for the mooring anchor is put over the side. When everything is in the water, the ship is positioned precisely over the desired mooring location, and a manual release is used which, when a rope attached to it is pulled, drops the weight at the correct location, and the entire array is pulled downward to the bottom, where it remains until the ship returns to ‘ping’ the acoustic release with the precise acoustic series of tones to retrieve it a year hence.

Hydrophone and acoustic release mooring components.

Float, weight, hydrophone and acoustic release.

Manual release for weight.

Bowheads were among the whales fairly heavily hunted during the golden days of whaling in the second half of the nineteenth century. Bowhead populations in advance of this period have been cited as about 16,000 animals, although of course, it is impossible to know for certain their historical abundance. The current estimate of the Beaufort-Chukchi-Bering Sea bowhead population is about 8,000-10,000 animals. The numbers of these whales seems to be stable and actually increasing. It is important to get good data on their numbers and habitat use as changes occur in sea ice and ship traffic in the Beaufort and Chukchi Seas.

Each year the bowhead whales migrate south through the Bering Strait in the winter to avoid seas completely covered with heavy ice, so that they can continue to surface and breathe. In the spring they migrate north from the ice edge in the Bering Sea into and through the Chukchi Sea, and many migrate north around Barrow and then east along the coast toward the Canadian arctic and Northwest Passage channels. Maps of the migration routes of some whales tagged by Alaska Fish and Game Department personnel can be seen at http://www.wildlife.alaska.gov/index.cfm?adfg=marinemammals.maps&name=8-10.jpg. As winter arrives, the whales return south along the coast to the Bering Sea.

Interestingly, the bowhead whales are often accompanied north by beluga whales (Delphinapterus leucas), the truly “white whales” of the northern seas. Because of their much smaller size, the belugas cannot easily break through the ice to make breathing holes themselves, and follow the bowhead whales using them as their own ‘icebreaking vessels’ to access more northerly waters in spring. Once in the Beaufort Sea the bowhead whales appear to distinctly prefer the waters closer to shore along the Alaskan North Slope, while aircraft sightings and tagged animals show that belugas remain further offshore in deeper waters, with a fairly distinct separation of habitat use. The fact that bowheads prefer the more nearshore waters along the North Slope makes them potentially more susceptible to increased human activities, and Kate’s project all the more important to contribute to continued monitoring of population levels.

Hunting whales by certain arctic peoples is much more than simply an avocation or way of harvesting food. This is perhaps difficult for outsiders to fully comprehend, but whaling in traditional Inuit and other arctic whaling cultures was, and still is, almost a religious or deeply spiritual enterprise, surrounded with rituals of moral purification and behavioral restrictions. It is still emphatically pointed out that one does not actually hunt whales, but one simply goes hunting for whales: it is the whale that gives itself to the hunter and whaling crew which has strictly maintained the traditions associated with successful whaling. In the arctic this invariably includes, among many other things, widespread distribution of the animals taken to everyone in the community, and other communities as well, practices which are still sustained. George Naekok, who is with us as an Inuit observer on this cruise, has been whaling most of his life.

Barrow resident George Naekok.

Insignia of the Barrow crew which includes George Naekok.