We continue to work in the Larsen B region, now just outside of the Crane Glacier fjord. The first light snow began to fall and the sea ice continues to consolidate, the only open water is now that from our channel, whereas when we began last week there was still open water along the southern coast. The sea ice, even though it is thin, makes swath mapping difficult as we have to cut a channel and resteam our track to get good data. We are also beginning to compile a set of nice sediment cores that record the inner portions of the ice shelf environment, one which is difficult to sample or examine in most places. But here the ice shelf collapse has provided open access to the workings of ice shelf, ice sheet transitions.
 |
Figure 1: Nikola captured the sun rise across a field of pack ice, ice bergs, and rising sea smoke. Such scenes were common for a while but now a low pressure system has locked in and we will be in cloud and overcast skies for the remainder of our cruise. |
 |
Figure 2: There is always the dirty job of cleaning up the bottom sampling equipment and here it falls upon Kim Roe (Hamilton College) and Cathleen Dale (Montclair State) to get the system ready for the next deployment. (Photo by S. Brachfeld) |
 |
Figure 3: A night launch of the kasten core might seem difficult but deck lights and lack of winds make it safe and efficient. We have been blessed by a lack of wind during our work, up till now. (photo by S. Brachfeld) |
As the polar winter descends, our world has begun to change. The open water of a week ago is no longer present and the pressing ice of the Weddell Sea pack has begun to fill the embayment. So at 4:00 pm local time (Clinton time as well) we decided that productive data collection toward the goals of our science program were no longer possible. I called Captain Mike Watson, the MPC Jim Holik, and the science watch chiefs to terminate science operations in the Larsen B region about 24 hours ahead of schedule. Our attempt to transit out of the region through the night has been slow going as we encounter a mix of bergy bits, growlers, and amalgamated multiyear ice all glued together with new ice and first year ice. Bergy bits are icebergs from glaciers that are hard and about the size of a car, whereas growlers are more the size of a house. Multiyear ice is remnant sea ice that has persisted for more than one year, one year being the normal life span of Antarctic sea ice. First year ice is ice formed last winter while new ice is that which has just formed. The mixture presents formidable obstacle because it is both deep keeled and has no one plane of weakness, just like plywood that is glued together is much stronger than a single sheet of wood of similar size. At present we are at 65 deg 22.5' S Latitude, 64 deg 49.21' W Longitude, the outside temperature is -11 degrees C, wind chill is -30 degrees C.
 |
Figure 1: View at about midnight of the 25th of April, looking astern along the starboard side of the vessel. Shown are the Cajun Cruncher (a small workboat) and one of two lifeboats. Surrounding the ship is the ice in which we are trying to navigate through. (photo by Taylor Burt) |
 |
Figure 2: View from the bridge (time lapse) of our attempt to see forward through the ice field using large spot lights. Changing wind and set direction complicate the navigation. (photo by Taylor Burt) |
During the night we changed strategy to try to exit from the tight pack ice of the Larsen B embayment. We cut back south, then east and currently are headed in the right direction (that is North) just southeast of Robertson Island. The going is tough as now we are in the true pack ice of the Weddell Sea in winter conditions. Large tabular bergs and multiyear ice cover the seascape, but it is easier going than in the mix of ice we were in yesterday at this time. We are averaging about 3-4 kt and hope to be out of the worst of the ice by nightfall. The outside temperature hovers at around -16 degrees C.
 |
Figure 1: As we bashed through the strange mix of sea ice and bergy bits some has landed on the back deck. Here the MTs and some of the Italian folks are trying to dislodge a solid chunk of bergy bit from the stern deck. (Photograph by S. Brachfeld) |
 |
Figure 2: The ice is not all frozen water. Along the bottom edges lay hidden growths of sea ice algae (mostly diatoms). These photosynthetic organisms can just get enough light at the bottom of the ice to make a living, but as the winter darkness grows their metabolism will slow down. Once spring comes the ice will melt and release the diatoms to the water to start a new season of growth in the surface layers of the Weddell Sea. Note the color layering which most likely delineates different concentrations or species composition. |
 |
Figure 3: We are also busy reducing the data. This is the colorimeter which V. Willmott has taught us all to use. It is used here by Kathleen Dale (Montclair State Univ.) and Sara Garner (Southern Illinois Univ.) to measure (cm by cm) the color spectra of the sediment core. This data will help us differentiate layers that we can't see with our eyes but which are important signatures of the origin of the sediment, the source, and the composition. |
April 28th brings us just off Robertson Island and the long three-day battle against the Weddell Sea pack ice has begun to show progress. Robertson Island was the locale that Sir Ernest Shackelton and his crew of the Endurance were aiming for while they drifted and edged across the pack ice of the Weddell Sea in 1915. It now rises off our port side as a impressive dome of ice, with a bit of dark rock along its southern tip. The island serves as the doorway to entering and leaving the southern waters of this region. Since it sits so far east of the mainland, pack ice can alternatively wedge against it (shutting the door) or blow out away to the east (opening the door). The ice is most definitely hard up against the island now, so the Palmer has to break down the door if we are to make our way north. We are almost through.
 |
Figure 1: Satellite image from NOAA of our present location (white cross) just off Robertson Island (coastline in green). The white patchy areas are tough pack ice (see other images from yesterday and today). The darker patches are light first and new ice, still formidable but easier to navigate. |
 |
Figure 2: A nice view of a tabular berg and our ship's wake taken some days ago, while we were still enjoying some open water. Photography by Nicole West (Colgate University). |
 |
Figure 3: Moon rise over the Weddell Sea. Photograph by Fabrizio Zgur (OGS-Trieste Italy). |
 |
Figure 4: Frost on pack ice, sea smoke, and icebergs. Photograph by Fabrizio Zgur (OGS-Treiste Italy). |
We finally busted out of the ice late last night and were able to make our way back north through the Prince Gustav Channel. Many old hands on board (including this one) said it was the worst ice they had ever seen down here. We are out of the brambles but not out of the woods yet. We had our last core station early this AM and it was a good one so now we are on our transit to the South Orkney Islands, some 500 miles to the east, north east. We should be there by Monday.
 |
Figure 1: A group photo amongst the relentless pack ice of the Weddell Sea at temperature of -20 degrees C. |
 |
Figure 2: Mate Robert Potter takes command of the bridge control as we attempt our break out from the Larsen B embayment. The stuffed Moose belongs to Kim Roe. |
Today is the last day of April and we left the Erebus & Terror Gulf late yesterday and are now speeding out toward the east, northeast and the South Orkney Plateau.We are still 24 hours from the first of a series of oceanographic moorings placed here some years ago by a team from Columbia University. Our goal is to retrieve one mooring and redeploy another. The moorings are lines of instruments anchored to the bottom by a large weight and tethered to a string of floats which keeps the more or less vertical in the water column. In such remote settings as the Southern Ocean these are the only means of determining oceanographic conditions over time spans of months to years. We are many miles from the nearest shipping lanes or surface traffic. Early yesterday we collected our last sediment core in the northern Prince Gustav Channel and at present are busy packing up our gear and stowing it away in our van for another, as yet to be determined, voyage.
 |
Figure 1: Pippa Halverson (an NSF post doctoral student at Toulouse University) and Kim Roe (Hamilton College, '08) sample our final kasten core (KC-11) for pore water. The chemistry of the pore water (the fluid that surrounds the mud) can be used to determine the pace and location of changes in the sediment composition such as the formation of the cold water mineral ikaite. Ikaite is often found in ancient rocks, mudstones that have signs of glacial activity, such as stones or rocks rafted by icebergs. Its formation remains a mystery but we have found some forming today in the mud that cover the seafloor in the Erebus and Terror Gulf. Hence understanding its formation here in the modern glacial setting of the Antarctic will help us understand its significance in the ancient record. |
 |
Figure 2: Nikola caught this group of sleeping crab eater seals on the pack ice. Since we entered the northern Weddell Sea we have seen an abundance of wildlife as opposed to the Larsen B region which seemed to lack any significant marine life, except a lone jellyfish reported off the Larsen Ice Shelf one cold morning. |
-- Commentary provided by Chief Scientist Eugene Domack
