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1500 feet above the ground surface is where our suite of instruments normally operates, but for this flight we are taking them up higher, much higher, in fact over 20 times our normal range to 33,000 feet. Our flight plan is to repeat lines surveyed in a previous years by NASA’s Land, Vegetation Ice Sensor (LVIS) a scanning laser altimeter. LVIS has collected data as part of the IceBridge instrument suite in the past, but it was flown separately at high altitude on its own plane, in order to map large areas of both land and sea ice. This flight will refly some of LVIS’s work but using a subset of the instruments on our plane, narrow swath-scanning lidar, the digital mapping camera system, the gravimeter, and our depth radar.
At our higher elevation we will fly faster and can cover a lot of ground. The landscape of Antarctica can be hard to get ones head around – a glacier catchment is usually too big to fit into one field of view, so we see it bit by bit, and try to build up a physical picture in the same way we build up our understanding of the system – piece by piece. We have flown several missions into the Amundsen Sea region on the west Antarctic coast in the past, but this was the first time where we could really see the context of all of these different glaciers – flowing into the same embayment, forming ice shelves, calving ice bergs, and drifting northwards through the sea ice.
The flight offers views of some of the most noteworthy features in Antarctica. Pine Island Glacier, one of world’s fastest streaming glaciers, developed an 18 mile crack along its face in the fall of 2011 which spread further over the last few months. The crack will inevitably lead to breakage, dropping an iceberg which scientists have estimated will be close to 300 pound in size.
Bordering the glacier is one of two shield volcanoes we passed over during our flight. Pushing up through the Antarctic white mask, Mount Murphy diverts the ice streaming along the glacier. A steeply sloped massive 8 million year old peak, Mount Murphy pulls my thoughts back New York as it was named for an Antarctic bird expert from the American Museum of Natural History.
From Mount Murphy we continue to the second shield volcano, Mount Takahe. Ash from 7900 years ago found in an ice core from the neighboring Siple Dome has been attributed to an eruption from this volcano. This massive potentially active volcano is about 780 cubic kms in size. The volcano was named by a science team participating in the International Geophysical Year (1957-8) after the nickname of the plane providing their air support …an unusual name for a plane as its origin is that of a plump indigenous Māori bird from New Zealand which happens to be flightless! Regardless the rather round Mount Takahe soars high above the glacier as we move overtop.
From there we fly over the tongue of Thwaites Glacier as it calves icebergs into the Amundsen Sea. To read more about Thwaites check out my first blog of the season: http://blogs.ei.columbia.edu/2012/10/18/launching-the-season-with-a-key-mission-icebridge-antarctica-2012/
For more on the IceBridge project visit:
Named after Edith Ronne, the first American woman to set foot on this southern continent, the Ronne Ice Shelf is tucked just to the East of the Antarctic Peninsula on the backside of the Transantarctic Mountains. With an area measured at 422,000 square kms, this is the second largest ice shelf in Antarctica. This vast icy expanse stretches into an indentation in the Antarctic coastline called the Weddell Sea, and gained some attention this past spring when scientists identified a mechanism that will force warming ocean water up against Ronne, which over time will cause it to thin and weaken (Hellmer, H. H. et al., 2012). Ice shelves are important barriers slowing the flux of ice moving off the land into the surrounding ocean. Any weakening in the tight connection of this ice to the land, either at the bottom where the shelf freezes to the ground below or where at the edges where it is tightly fused to the continent, can have major impacts on the speed and volume (flux) of ice moving off the land and into the oceans.
The current mission is being flown to measure the flux of ice currently coming into the Ronne Ice Shelf from the surrounding Antarctic landmass. To determine this we focus on the ‘grounding line’, the area where the ice changes from being frozen solid to the land below to floating as part of the ice shelf. To understand how much ice is moving over the grounding line, we have to understand how much ice is at the grounding line, and to do this we have to fly along the grounding line (or slightly inshore of it).
In many areas of Antarctica, even knowing where the grounding line is takes a lot of work. Much of that work is done using satellite data through a process called “interferometry”. This process compares the returning radar signal from different satellite passes to determine where the ice begins to move under the influence of the ocean tides. In this scale, ice that is responding to the rise and fall of the tides is floating ice, and from this we can mark the grounding line. While technique identifies the grounding line, it does not show how much ice is moving across it; to determine that we need to collect ice thickness measurements. For today’s flight we moved just inland of the grounding line for about half of the Ronne Ice Shelf collecting ice thickness and other supporting data that will begin to fill in this important information.
Reference: Hellmer, H. H. et al. Nature, 2012. DOI:10.1038/nature11064.
For more on the IceBridge project visit:
By Ana Camila Gonzalez
“But can’t you see the rings already?” I ask, wondering why I’ve been asked to sand a sample- it sounds to me like one would damage a sample by subjecting it to the mechanical screech of a sander.
“Yes, but under the microscope they look foggy if you don’t sand them. Also, you’re looking at a black oak sample. You wouldn’t see any rings before sanding if you were looking at a Maple, for example.” Jackie responds. She shows me a maple core sample that she explains has been hand-sanded down to a 1200 grit. It’s smooth and shiny as can be; yet I can barely see what seem to be hairlines.
“Oh. That makes sense.” I secretly hope I won’t have look at another maple sample for a while.
I approach the machine. I look like a character from BioShock or a WWII soldier in the trenches, as I am wearing a respiration mask, goggles and ear muffs. Seemed a little excessive to me at first- once I turned the machine on and I saw the mushroom cloud of sawdust come off the banshee-screeching sander, however, I realized I’d be better off looking like a biohazard worker than having to bring an inhaler and hearing aid to work.
I place my first sample down on the sander, but it flies off and hits the wall… I guess I can hold it tighter and push it down a little harder. I try again but this time my sample stops the belt from spinning. Definitely too hard. Eventually I get just the right amount of pressure, and I realize I can tell because my sample looks clearer every time I take it off the belt. I start humming to myself, singing something along the lines of I can see clearly now, the rings are there… As I go to higher and higher grits and my sample starts developing a cloudless luster, I realize I enjoy this a little too much.
To me, sanding is a process full of Zen. It’s a process I can focus on while still letting my mind wander, and my thoughts usually get pretty philosophical- I have this foggy, unclear sample and slowly I take off its layers and layers of disparities. What results is a core in its purest form ready to tell the story of its life, and after a few hours of sanding I’m ready to listen.
Ana Camila Gonzalez is a first-year environmental science and creative writing student at Columbia University at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory. She will be blogging on the process of tree-ring analysis, from field work to scientific presentations.
One piece of our IceBridge mission focuses on sea ice here in the south. Sea ice in the northern regions has been reducing at dramatic rates over the last decade, setting a new record just this year, but the story in the south is not so clear. In fact, there has been a buzz that Antarctic sea ice extent may just be increasing while the Arctic ice is decreasing. The issue is a complex one and involves not just sea ice extent (how much surface area the ice covers) but sea ice thickness (total volume of ice). While the extent of Antarctic sea ice is increasing, we also need to understand how the thickness is varying.
One of the trickier items in measuring sea ice is making the raw measurements of thicker and thinner ice. With only satellite measurements it is hard to get the true thickness of the ice, since the surface of the ice is often covered with snow that needs to be accounted for in our calculations. Using the snow radar on the IceBridge mission we can work out how much of what the satellite is measuring is actually snow.
The Bellinghausen Sea sits just to the west of the Antarctic peninsula and in the southern winter months is generally covered with sea ice. We have flown two Bellinghausen sea missions this season – one to map out to the furthest edges and another to looks at the gradient of sea ice change as you move away from the coast or shoreline. The second Bellinghausen mission was important because in running profiles in and out from the coast it allowed us to measure how ice thickness patterns vary with distance from the shore. We need to understand these patterns of ice thickness in the southern end of the planet, how they may be changing and what connection they have to the climate system.
There has been much less study done on southern sea ice than northern sea ice because we get very few opportunities to make the measurements we need. We have two high priority flights to the Weddell Sea (on the eastern side of the Antarctic peninsula), but so far it has not been possible to fly them because of the weather. Hopefully before the end of this season we will be able to fly both these flights and fill in more pieces in the sea ice story.
For more on the IceBridge project visit:
Last year IceBridge had its first flights into East Antarctica when it flew some missions into the Recovery Glacier area. Recovery is a section of Antarctic ice that lies east of the peninsular arm of West Antarctica, tucked behind the Transantarctic Mountains, a dividing line that separates west from east. We know from Satellite data that Recovery and its tributaries have a deep reach, stretching well inland to capture ice and move it out into the Filchner Ice Shelf draining a large section of the East Antarctic ice sheet. But there is a lot we don’t know about Recovery because the remoteness of the area has limited the number of surveys.
Several recent works have showed us that this area is important. Satellite measurements of the ice surface show small patches along the trunk of the glacier that are changing elevation more than their surroundings. These patches have been interpreted as lakes that lie under the ice sheet, coined the Recovery Subglacial Lakes. The lakes appear to drain and refill over time as the surface elevation over the lakes changes. To learn more about them and what they might tell us about the behavior of the glacier, we need to look under the ice.
But there is more we need to understand about this remote area, including simply needing to know the size and shape of the channel that delivers this ice out to the ice shelf and towards the Weddell Sea. Last year’s mission gave us some data points to outline the channel, but this year will help us provide a more complete imaging of what lies below this East Antarctic ice conveyor belt.
We will fly cross sections along the lines of the retired ICESat satellite tracks, allowing us to compare the laser measurements we make of ice surface elevation to those made during the satellite mission. We will end the day flying along the Recovery channel to get another look at one of the interpreted lakes. Combining last years’ data, ICESat data and this year’s data will give us a better picture of the area that has been carved beneath the Recovery glacier, the amount of ice that can be moved through the glacier and its tributaries, and how the lakes under the ice might fit into the larger story.
After waking up in the Rupsa River in Khulna, we watched as the Vanderbilt University group studying sedimentation around Polder 32 arrived on Bachchu’s boat. They pulled up alongside and we spent some time catching up with each other’s trips before it was time to hit the road. Our last site is nearly at the northernmost tip of Bangladesh. This one is for tectonics. The 2-km high uplift block of Shillong, is roughly coincident with the Indian state of Meghalaya (Abode of the Cloud). It was the site of a M8.1 earthquake in 1897, although the exact fault that ruptured is uncertain. Our existing GPS indicate that it is moving south at ~7mm/y, but there is a suggestion that it is rotating clockwise, meaning the western end would be moving slower. Our GPS is going in Bangladesh just to the west of Shillong. However, the Brahmaputra River has eroded away the western margin and buried the remnants under sediments. We have to be far enough north to be on the Shillong-Assam block and away from the several faults on its southern side. We settled on the town of Bharungamari. It is literally the end of the road, only a few miles from the Indian border.
So we set off on a 400 km drive. Along the way, we stopped at Kushtia and visited Humayun’s childhood home and met his sister-in-law and nephew. Then lunch and across the Ganges River. At our first flat tire, we has tea in a small shop – Humayun had them pour boiling water on the glasses for us. At the second it was green cocoanuts. The driver switched to the spare tire while Sarah attracted a large crowd of locals. When we finally got to the hotel it was almost 10pm, about 12 1/2 hours after we left the Kokilmoni. At least it is one of the nicer hotels that I have stayed at in Bangladesh.
The next morning was a more leisurely 8am departure. For breakfast, we were joined by Atiqulla, one of Humayun’s fourth year students who is from Bhurungamari. He scouted the site and would lead us there, the local hospital. We squeezed the extra person into the van and headed north. We got there late morning, scouted out the roof and located a site for the antenna and for the receiver. Getting there meant walking through a hallway with beds containing patients at the hospital. It seems we have had two modes during this trip, either start very early and then have breakfast at noon, or have breakfast first and then have lunch after 4pm. This was the latter. You could tell we were getting worn out. We were having more trouble keeping track of some of the small screws and tools we needed. We started running out of anchors for attaching cables to the wall. Still, we got it done, although it is not our prettiest site.. However, Humayun did a great job with the grounding rod, having a channel cut in the concrete apron around the building, running the wire through a conduit and then recementing over it.
By the time we were done, it was 3:30 and the hospital administrator and some of the staff came to see the site. By the time Humayun finished explaining th purpose of the GPS, we were more than ready to get some lunch. What I didn’t know was that we were invited to Atiqulla house for lunch. We went to the house of his extended family, parents, siblings and nieces and nephews where we were served a feast. The five of us ate while the family and a large group of neighbors looked on and chatted with us. We had chicken, squab and beef along with boiled and pilao rice, paratha (bread), vegetables, dal (lentils), and cucumbers. A veritable feast and a good ending for the last GPS installation.
We stuffed our selves and headed back to Dhaka, staying overnight at Bogra, 4 hours away. Along the way we passed celebrations of Durga Puja, the largest Hindu festival in Bangladesh, and lots of cattle and other animals being transported for Eid ul-Azha, the feast of the sacrifice, to be celebrated this weekend. After arriving in Bogra, we celebrated with a beer at the first bar I’ve ever seen in Bangladesh.
We sailed out of the small channel we were anchored in to the Sibsa River and then to the south. We passed the western side of Polder 32 with a good view of the embankment that protects the island then passed into the Sundarbans forest with mangrove trees on either side of the wide river. Hiron Point is close to the mouth of the river where it empties into the Bay of Bengal. Perhaps empties is not quite the right word as the river is tidal, flowing both ways. Moreover, the mud that maintains the Sundarbans probably comes from the sea. The sediment discharged by the combined Ganges-Brahmaputra-Meghna Rivers is swept westward along the coast and some of it is carried inland by tides and storms. How much is still a topic of research. We prepared the equipment in the bow while watching for tigers along the shore. We reached our anchorage after about 8 hours and enjoyed a BBQ on the top deck. Then, at last, an early night.
Just after 6AM we loaded the launch and headed into the channel with the forest station after watching the sunrise. We were accompanied by two armed guards, required in the Sundarbans, although we don’t expect tigers at the ranger station. The first thing we passed was the tide gauge, the reason we are putting the GPS as this particular location. It is well known and its data is available in a global repository for tide gauge data. We landed at the third dock belonging to the forest service. The path to the ranger station proudly announced the Sundarban as a World Heritage Site and through in a couple of caged tiger statues as well. We met the forest ranger and were told that there is no cell phone service, contradicting what we had been told. During the winter there is a weak signal. That was going to be a problem for downloading the data. We headed to the roof and for once, the ladder was already in place.
The roof had a low brick wall around its perimeter. Brick is much weaker than reinforced concrete and not considered stable enough for GPS. Our two foot threaded rod was long enough to get us 5” into the concrete is we drove the long drill bit all the way to the chuck. It would have to do. The GPS went into a secure room with communications equipment. By now our experienced team split into our familiar tasks. Sarah figured out a way to get the cables to the roof by tying them to a rope after going through the wall. After some effort, I managed to drill the wall to the maximum depth. With the poor to nonexistent cell signal, we set up a yagi directional antenna and pointed towards the closest cell phone tower some 60 km away.
We got everything set up, but the cellular connection didn’t work. Next step is to hope that we can establish a connection in the winter and be able to seasonally download the data. Having to return regularly to download the data or come back to set up a radio link would be expensive, although the Sundarbans is a wonderful place. We said our goodbyes and headed back to the M/V Kokilmoni without having seen either a tiger or a crocodile, although we saw a lot of mudskippers, a personal favorite of mine while leaving.
We weighed anchor and headed back north to Khulna. The crew spotted a crocodile, but I missed it while uploading blogs. Going north, we had left the calm of the Sundarbans and returned to the modern electronic world of cell phones and internet. One more GPS to go, but it is in far northern Bangladesh, a 380 km drive from Khulna where we get off the boat tomorrow.
When we finally got to Khulna, the second largest city in Bangladesh, Bachchu, who organized the boat, met us and led us down country roads to where we met our boat, the M/V Kokilmoni, our home for the next few days. It is very large for the four of us and Bacchu, but faster and safer when there is still a risk of cyclones, as hurricanes are called in the Indian Ocean. Luckily the forecast is for 10 days of clear sky and 90° weather. When we got to the dock (ghat in Bangla), a crew from the ship was there with the launch to ferry us and our loads of equipment to the ship. After stowing it all away, dinner at a reasonable time.
The Kokilmoni sailed down the channel to near the location we will install our GPS on Polder 32. Back in the 1960s, Bangladesh (then East Pakistan) constructed embankments or polders around much of the low-lying coastal region. The region is crisscrossed by numerous interconnecting rivers separating the land into islands. The government built embankments around many of them to protect them from flooding. However, they also prevented the sedimentation necessary to maintain the land. Without either flooding or sediment, the sediments compacted and the land subsided so that it is now 3-4 feet below the land outside the polders that continue to get sedimentation. This set the stage for Cyclone Aila in 2009 and the storm breached the embankment in multiple places. Initial repairs did not hold and the island was submerged for most of two years. What should be done for the poldered areas in the face of continued sea level rise is a major question. Our GPS will provide much needed data on the rate of subsidence.
Polder 32 is a main focus site of a large project funded by ONR, the Office of Naval Research. This project looks at not just the physical side of the balance of sea level rise, subsidence and sedimentation, but also the local population’s interaction with the environment and their potential response to disasters, such as temporary or permanent migration. In fact, social scientists make up the most of the project. The lead institution of this project is Vanderbilt University and there is a group of them here at Polder 32, too. Unfortunately they are on the opposite side of the island, so we were unable to meet up. Neither of us had the few hours to spare to sail over to the other.
Anyway, we again prepared the GPS equipment into the night, then work up early to install the GPS. At least on the Kokilmoni, there was tea and cookies to help us cope with the 6AM start. Plus we had a crew to help carry everything to the site, including a very heavy diesel generator to provide power for the drill. They dropped us off at a dock connected by a bamboo bridge to shore, then moved to a place where they could offload the equipment. They insisted on carrying everything for the 1-kilometer walk to the elementary school we will use.
In May, Dhiman and Steve did an elevation survey of the entire polder and set up a reference station at the school. Then they left the GPS there to get a head start on collecting data with a temporary “campaign” set up. When we got to the roof, we saw the installed antenna, but the GPS had failed. The flimsy portable solar panel could not hold up to the monsoon. Still the data for May and June it go will be valuable and the antenna is already installed. After a discussion with the headmaster about where to put the receiver, we put it in their computer room (solar powered). Just outside is a statue of the Hindu goddess of education as this village is almost entirely Hindu.
We went to work, with our now experienced team splitting up the tasks, with Sarah doing the most technical parts. I drilled the holes in the roof and bolted the solar panel down and secured the antenna cable to the roof. When it was done, we headed back to the ship to head to Hiron Point in the Sundarbans, the world’s largest mangrove forest and nature preserve that is home to 350-400 tigers. And we finally got to eat a lunch at a reasonable time. As a Sundarban tourist boat, the Kokilmoni has very good food.