Press Archive

Greetings from the South Pole

SDSC Iceberg Researcher Joins Antarctic Expedition

Published 03/23/2009

Returning to Antarctica eight months after a previous expedition, a research team led by Ken Smith, senior scientist with the Monterey Bay Aquarium Research Institute (MBARI), continues to study biogeochemical cycles around icebergs. This third expedition, underway until April 15, is providing scientists the opportunity to study the pelagic ecosystem both near and further away from icebergs during prime growing conditions. Together, the scientists will target three to four tabular icebergs during their 40-day mission in the Northwestern Weddell Sea.

On board the research vessel ice breaker Nathaniel B. Palmer is John Helly, director of the Laboratory for Environmental and Earth Sciences with the San Diego Supercomputer Center at the University of California, San Diego. Now on his third research cruise to the region, Helly is responsible for measuring the physical geometry of icebergs using oceanographic and meteorology instruments, computer systems, laser ranger, and an inclinometer.

Posted below are random logbook entries from Helly, giving readers a glimpse into the daily life aboard a research vessel navigating though often severe conditions. Entries will be made whenever possible, due to limited email and Internet service. Visit the MBARI website to view additional entries from other crew members, research updates and to track the ship's voyage.


LOGBOOK: JOHN HELLY



Iceberg III: Iceberg Hunting in the Weddell Sea

8 April 2009 / 0841Z

Latitude -062 49.0514
Longitude -050 06.3565
Air Temp -2.3C
Wind Chill -9.8C
Sea Surface Temp -0.702C

Moonlight over Antarctica has finally been realized. I just went up on the bridge to set up our next surface mapping operation and there was a nearly full moon backlighting an iceberg on the horizon and lighting up the ocean surface all the way to the ship. I've been trying to see the moon for weeks but the overcast has not been cooperating. We are now running a box pattern that I'm using to allow us to cover a lot of territory, about 100 square-nautical miles, in just less than 6 hours at 11 knots. This is the last week of measurements before we head back to Punta Arenas so I'll recap all the haps since my last note.

At last report, we were headed for B15L. Well, that turned out to be a bummer because it was embedded in a huge chlorophyll bloom due to phytoplankton that famously grows at the melting edge of the sea ice boundary. That's wonderful for the biota but not so good for our science. We need icebergs that are out by themselves in water that is unaffected by other factors. It was great looking iceberg, though, and we did a circumnavigation of it so I was able to measure the area of it from the ship and the transit to it added a lot of information to our surface map. Once leaving B15L, we headed west to 'iceberg alley' to get a look at other targets. Most of those turned out to be non-tabular collections of sea-ice and near-shore ice so we continued north back to C18A to make some additional measurements and drop another GPS tracking unit on the iceberg. The flight was successful in dropping the tag and we recovered the airplane onboard with a spectacular landing.

Our next adventure was to find a control site, away from C18A, that we selected from some of the previous surface mapping results. For those who might not be familiar with the jargon, a 'control site' is a place that can be used to compare an 'experimental site' with to determine whether there is a difference between them. We are looking for differences due to the presence of a melting iceberg so we went somewhere that there are no icebergs, hopefully where none have been for a long time, and where we find homogeneous physical oceanographic conditions. I won't get into all the details of what establishes the bona fides of a control site since this can be endlessly debated, and can devolve into nearly religious debates, but we found something that suits the bill and that we were able to drive to in a reasonable amount of time.

We spent a few days there conducting a variety of water sampling hydrocasts, MOCNESS trawls and water pumping tows and then headed off to return to iceberg alley. We wanted to go back to iceberg alley because there was a very large number, and high density, of small icebergs that were clearly and spectacularly derived from continental glaciers. They contained many vari-colored deposits of dark, presumably terrestrial, material that has the chemists very agitated about looking for strong terrestrial isotope signals. So, we spent a few days there as well and we are back there now.

The abundance of life here is strikingly greater than anywhere else we have been. Seals, penguins, birds of all sorts, and whales are frequently seen. The other day three humpback whales stayed with us for most of the day while we conducted ROV operations but we never got a look at them with the ROV. It's definitely colder here but just chockfull of weirdly shaped icebergs with all kinds of streaking and odd geometry. Most of what we have been doing here is to try to characterize a broader area of ocean subject to the influence of melting iceberg to see if we can establish a connection from the individual iceberg measurements we have been making to an area that has a large number of smaller icebergs distributed throughout it.

We have few more operations to complete in this area before we head north on Thursday night. One of those includes another flight by our air force to drop a newly designed and fabricated type of delivery system to put the GPS tracker on the ice. We have suspected that the previous packaging was being buried by ice or snow after deploying and the new design will, we hope, be better able to resist being buried. That will be an interesting experiment in itself.

The weather today and yesterday has been clear and the seas very calm so that we are able to enjoy some of the sunshine on the deck. I'm seeing a few slightly sunburned faces and it reminds me that summer is coming in the northern hemisphere and that I'll be back in San Diego in a little more than a week after forty days on this ship. Strange thought and it seems worlds away.

--

24 March 2009 / 0505Z

Latitude -063 54.40073
Longitude -045 42.5214
Air Temp. 1.8C
Wind Chill -14.5C
Sea Surface Temp. -0.214C

Today was great in a lot of ways besides having a good sleep. It was the first sunny day in more than a few, and, most importantly, we completed our already productive work at C18A with a couple of big successes and we are now on our way to our next iceberg, B15L. B15L is a descendant from B15, the famous iceberg that broke away from a shelf in the Ross Sea in 2000. The Ross Sea is on the other side of West Antarctica from where we are in the Weddell Sea so we get to look at a visitor from a far away place.

Fragments of this monster, ~11000 square kilometers (4247 square miles), have been making their individual way around the continent so that we will now have the opportunity to investigate one of them. You can get an idea of the nature of the journey of B15L by imagining a similar iceberg departing Seattle and ending up in Manhattan. This is not a great analogy for a lot of obvious reasons but it gives you an idea of how extraordinary it will be for us to have a look at an iceberg from a completely different part of the continent. B15L has come to the Weddell Sea by a journey all the way around the continent from the other side of the Antarctic Peninsula to where we are now.

The naming of icebergs is a curious matter. It isn't just one of your everyday games. You may think that I am as mad as a hatter, when I tell you an iceberg can have four different names. First, there is A** if it comes from where we are, or B**, if it comes from a place further west. Also there's C** if its accent is Kiwi or D** if its origin is the northeast quadrant. . (Apologies to TS Eliot). The ** is just a serial number that identifies an iceberg from one quadrant in the order it is discovered, usually by satellite remote sensing.

A - longitude 0° to 90° W (Bellingshausen Sea, Weddell Sea)
B - longitude 90° W to 180° (Amundsen Sea, Eastern Ross Sea)
C - longitude 90° E to 180° (Western Ross Sea, Wilkesland)
D - longitude 0° to 90° E (Amery Ice Shelf, Eastern Weddell Sea)

This is probably more than you wanted to know about iceberg names but there it is. If you look at a polar-centric map of Antarctica you can see this four-quadrant organization quite readliy

We have been running away from another low pressure that has been 'pounding' Palmer Station and is as big a low as anyone onboard has previously seen. However, and yet again, after ominous reports of huge seas and winds, we are smoothly cruising our way to B15L for 30 hours of run-time. A little bit of bump here and there but it looks like we dodged another bullet. We should arrive there at 1700Z today. The Z means Zulu which means UTC which means Universal Time Coordinated which means Greenwich Mean Time (GMT). As you can see, time is also very complicated.

The big successes at C18A relate to our ability to detect and visualize the meltwater plume from the iceberg and the use of the other sampling devices that we developed and refined during the June 2008 cruise. These relate to 2D and 3D visualization of the meltwater from the iceberg, the measurement of organic matter (i.e, carbon) export from the iceberg vicinity using the LST, and the collection of water from the iceberg surface and close-proximity surveys of the ice surface and associated biota from the ROV. The pelagic (! look it up) trawl, called MOCNESS-1 and MOCNESS-10, have also worked quite well through as a result of very thorough preparation by the trawl team.

Through a combination of techniques, we have mapped the meltwater plume in 2D in terms of sea surface temperature, salinity, chlorophyll, fluorescence, transmissivity, pCO2. We have also been able to map the sub-surface volume of the plume using hydrocasts, lowering an instrument called a CTD on a wire through the water column, and creating 3D images of the resultant measurements. The pictures are very nice and beautiful and provide our first look at the way in which the icebergs influence the water in which they are immersed. Sorry I can't send some along but we are bandwidth-challenged here.

We have also had big successes with the LST (Lagrangian Sediment Trap) and the ROV. The LST was deployed and travelled under C18A as planned and, most importantly, successfully recovered after some nail-biting searching for it after it was commanded to surface. A combination of techniques was used to locate it and ultimately a signal from the LST to a satellite was then related to the ground, reported to a colleague at MBAR and communicated to the ship. These coordinates put us within a small enough search radius from the surfaced LST such that it could be radio-located from the ship and recovered. The ROV has been wandering all over the ice-face and has been collecting HDTV imagery and has, we think, plumbed the bottom of the iceberg at ~200m.

Laser measurements of the freeboard (i.e., the tip of the iceberg) put it at 27m in elevation so we get about a 7-to-1 ratio of depth to height for C18A. You cannot make too much out of this since we know the ice mass is not uniformly distributed below the water but it's hard to resist calculating these ratios.

I'd like to write more about the whale that surfaced underneath me while I was making laser measurements from the bridge wing, 80 feet above the water, or the, once again, near-frostbite of my fingers while holding on to that instrument in a strong headwind. There was also the curious incident of a group of land-birds, possibly egrets, that landed on the ship during a snowstorm the other night and were found on deck the following morning. In case it's not obvious, there shouldn't be any landbirds around here. They didn't last more than a day, unfortunately, and were a poignant reminder that life and death goes on around us all the time while we blissfully go our merry way. But that's about as far as I can go tonight, or this morning, whatever it is. More to follow from the escapades around B15L.

--

11 March 2009: NBP0902

Latitude -062 16.8061
Longitude -051 35.8667
Air Temp. 1.8C
Wind Chill -11.4C
Sea Surface Temp. 0.087C

We are on station at iceberg C18A after leaving Punta Arenas last Friday, 6 March, at 1000 hrs on the RVIB Nathaniel B. Palmer. The passage across the Drake was a bit tense since there was a big low waiting for us. It passed to the south just enough to leave us alone and we continued over in the direction of Clarence Island with the intention of spending a few days in the lee there to do some instrument and procedure testing. When we arrived there, two days ago, the winds, from a different low, were 35-45 knots and too much for the testing that we wanted to do. So we moved on to find the nearest target iceberg I've been watching with remote sensing data, C18A.

We've got a new ROV (remotely operated vehicle), four airplanes, two of which are bigger and more powerful than our last cruise, and some additional Lagrangian sediment traps (LST). The LSTs are designed to be deployed upstream of an iceberg where they are commanded to submerge and drift along below an iceberg to collect any debris that is falling from the melting ice as it cruises below it.

I've been working to develop the surface mapping techniques and analysis software that I started on the June 2008 cruise and am very happy with the progress on that. It is coming together very nicely and I now have the help of a 3rd year graduate student in physical oceanography from Scripps. We are developing some new methods of looking at the very fine-scale structure of the circulation around the icebergs from the acoustic doppler current profiler (ADCP) that is mounted on the hull of the ship. All of the data that we are accumulating from the various sensors is being ingested into the digital library framework (DLF) software that I've been working on for quite a few years and that is also working very smoothly.

The hours have been pretty long since I'm in that initial phase of excitement, anxiety and anticipation about finding the first iceberg since that's part of my responsibility. Before yesterday, I had been up for almost 48 hours with only a couple of hours sleep. I didn't realize how much stage-fright I was experiencing until we found this beautiful iceberg, C18A, that I'd been tracking courtesy of data from our colleagues at BYU. It was kind of deja vu all over again like the experience I had with A52 in 2005. At that time, the first time I ever did this, we were driving to the location where I predicted it to be and got there and there was nothing there. Turned out to be because the iceberg was moving at 2.5 knots and was about 25 nautical miles from where the last image suggested it would be. We did find it and it was huge.

This time we got within 24 nautical miles of where I expected to find C18A and, with the radar on 48 miles range, we didn't see anything like C18A. I experienced the same kind of 'Oh ****' but also had the benefit of understanding the limits of shipboard radars better. So we kept on heading to the expected location and within 40 minutes we had found this very substantial iceberg and proceeded to circumnavigate it in 0.25 nm visibility; fog and snow. It's 32 kilometers (~17 nm) by 6 km (~3). We went all around the iceberg using only the radar for about 7 hours and have a nice digitized perimeter but we never saw the iceberg during all that time. This morning it is bright and clear and lovely. After getting done with that 48 hours, I crashed all day from 0700 to dinner at 1730 and felt fantastic when I woke up. Now we can seriously get to work after breakfast.

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