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.

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!

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.

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– After a four day trek looking for other icebergs we might want to study, we came back to continue studying iceberg C18A. Iceberg diversity and how it affects surrounding ecosystem is one of our goals. If the icebergs are delivering nutrients, one of our main hypotheses, we expect to see big changes when the iceberg is traveling in nutrient poor waters. The trick turned out to be how to find these nutrient-poor waters in the Weddell Sea. Looking at published nutrient values it seemed that the central Weddell Sea, far from the coast, could be a good possibility. From satellite pictures we speculated that B15L, an iceberg from the Ross Ice Shelf, could be in such waters.

As we arrived at 65º 28.362’ S, 40º 56.856’ W, B15L was surrounded by the biggest phytoplankton bloom we have seen on this cruise. Instead of half a milligram of chlorophyll a per liter we encountered ten! These waters did not seem poor in nutrients at all. The iceberg was large, tabular and somewhat more square than C18A but of similar size and characteristics. It would have been perfect for our studies. After taking a first look at the iceberg, many pictures, samples for phytoplankton and nutrients, we decided these conditions were not conducive to answering our questions. The ice edge was less than 100 nautical miles to the south; B15L was trapped in what is known an ice-edge bloom, one of the best studied high productive areas in high latitude oceans.

B15L as seen close to the ice edge in the central Weddell Sea. This iceberg has traveled from the Ross Ice Shelf half a continent away.

The ice edge bloom was dominated by diatoms. A high diversity showed many new species not sampled so far. Several Chaetoceros spp. were very characteristic: chain-forming species with interlocking spines.

Dominant diatoms at the ice-edge bloom close to B15L: Chaetoceros spp.

How best to continue our studies? Keep looking for a new iceberg in the middle of the Weddell Sea or go back to where satellite images show icebergs abound, the Iceberg Alley? We decided for the latter. In another 24 hours we were back to the western Weddell Sea. We decided to study C18A for a few more days; there were many unanswered questions still. So we are glad to have a second opportunity. A few things are different this time around. C18A had kept moving towards the NE and its position is now more along an East-West axis than a North-South one. We will be here for the next 3 days and sampling has already started.