Petermann Glacier 2015

Introduction to the Petermann Glacier Expedition 2015

Click to enlargeThe Petermann Glacier is located in North-West Greenland where it drains the northwestern sector of the Greenland Ice Sheet (GIS) into the Nares Strait. It is a so-called tidewater glacier, also known as outlet glacier, with an approximately 70 km long and 15 km wide floating ice tongue, or small ice shelf. The floating portion varies in thickness from ~600 m where it is grounded at the seabed in the inner part of the fjord to ~30–80 meters at its front.

The Petermann Glacier 2015 expedition with IB Oden focuses on investigating marine cryospheric and oceanographic changes in the Petermann Glacier-Fjord and adjacent Nares Strait region that are accessible in geologic records. Long term records of variations of glaciers draining the GIS into the ocean and their interaction with the ocean are required to fully understand the dynamics of the GIS.

The Petermann Glacier is a well-suited target because it terminates in an extensive floating ice shelf that is sensitive to ice/ocean interactions. Furthermore, the glacier has a relatively simple geometry that can be resolved by realistic field programs. Finally, the Nares Strait is a conduit for southward flow of low-salinity waters, with oceanographic impacts. The general cruise area is shown in Figure 1 along with the transit track to the study area along the west coast of Greenland.

The Petermann Glacier 2015 expedition is further described at the Swedish Polar Research Secretariat's web: http://polar.se/en/expedition/petermann-2015 

You can also follow the expedition through Twitter @Petermann_Ice , Instagram petermann_ice  and at https://petermannsglacialhistory.wordpress.com  blog.

 Martin Jakobsson will be writing a blog starting on July 26

Oden online tracker (click on the map to follow Oden )

 

 Skidbladner, the boat that always sails downwind no matter the wind direction

Onboard the Oden we have the RV Skidbladner, a 6.4 m long aluminum boat equipped with a bow mounted high-resolution multibeam echo sounder and sub-bottom profiler. The name Skidbladner is derived from Norse mythology. Skidbladner was the god Frej’s magic ship that could be folded to fit in a pocket when not needed and could sail over both land and sea with the wind always from behind no matter the wind direction. All the gods from Valhalla fit inside Skidbladner. This magic ship was built by the sons of Ivaldes, ruler of the dwarfs of the underground. We need these magic ship capabilities as we are released from Oden into the pack ice to map the unknown seafloor along the mysterious and dramatic shores of the Petermann Fjord and nearby.

Our specific Skidbladner targets have been the outlet glaciers that calve icebergs and act as sediment providers to the fjord. Oden has kept a distance of about 1–2 nautical miles from the extremely steep walls of the Petermann Fjord and the outlet glaciers. Apart from the multibeam echo soundings collected in the fjord by US icebreaker Healy and Canadian Amundsen 2003 and 2012 respectively, most seafloor was unmapped before we began the expedition. For this reason, we had to map with Oden systematically from the deep central part and outwards towards the shores. With Skidbladner we are able to go up next to the glaciers and map the seafloor and water column properties directly at their margins.

The procedure with a Skidbladner operation starts with placing a RTK (Real Time Kinematic) GPS reference station somewhere on the nearby shore. From the RTK station information is sent by radio to Skidbladner’s GPS that uses this to increase the accuracy from meters to centimeters. In addition, we are able to use the GPS height information to correct for the tide variations during our survey. Once the RTK station is mounted and we verified that we are able to receive information onboard Skidbladner, it is launching time. The launch procedure has gone extremely smooth, although we were forced to cancel launches on a few occasions when the wind was too strong. Once Skidbladner is launched, we climb onboard and off we go to map our targets!

Sven Stenvall (Kallax Flyg) and Björn Eriksson (Stockholm University) setting up the RTK (Real Time Kinematic) GPS reference station on a mountain on Hall Land outside Petermann Fjord.

Launching of Skidbladner from Oden. Photo: Björn Eriksson

All five Skidbladner missions have been mesmerizing experiences. Once down at the sea level, away from everything, the glaciers and icebergs grow in dimension. We went up to the glacier fronts, but with a steady hand on the throttle in the event that some ice would decide to break away. The advantage with a small boat is that one can move away really quickly if needed. One of the more difficult parts has been to navigate between the sea-ice flows since we do not get the “birds view” one get from the 23 m high bridge on Oden. We do not easily locate all openings between flows that off course are impenetrable for us anyway. At moments it was necessary to climb up on the roof to sufficiently see our path through the ice. While larger flows are easy to pass around if a passage exist, the greatest challenge has been to make sure we do not run into smaller pieces of ice with the bow-mounted sonar. For this reason, we have had one person on guard all the time at the bow.

Skidbladner surveying along the margin of an outlet glacier in Petermann Fjord. Kevin Jerram from Center for Coastal and Ocean Mapping, University of New Hampshire, is enjoying the close up view of the glacier margin. Skidbladner mapping along the Petermann ice shelf margin. The thickness of the margin varies and this is one of the thinner stretches. Rezwann Mohammad from Stockholm University is here guarding the bow mounted multibeam sonar.

The final Skidbladner mission aimed to explore the entrance to Bessel Fjord, a completely unmapped fjord where, to our knowledge no boat has ever previously entered, at least not to map. Bessel Fjord is extremely narrow with steep walls and run parallel to Petermann Fjord. There is an island at the fjord mouth made of what appears to be a terminal moraine. The fjord must have hosted a smaller ice stream at one point. We are interested in Bessel Fjord since it must have acted, and still is, as a huge sediment trap and thus its bottom should contain a thick pack of sediments of high temporal resolution that could be cored for environmental studies. However, since no one has previously measured the sill depth next to the island we were not able to enter with Oden and take sediment cores. Next to the island, sea ice and icebergs from the smaller outlet glaciers calving into the fjord have become stuck and accumulated in masses. The tidal currents across the sill were strong and ice moved like crazy. What appeared to be a relatively clear entrance with openings in between the ice flows during the morning’s first helicopter was rather clogged by ice when we arrived. Regardless, we made an attempt to drive in with Skidbladner, much like playing the good old computer game “Asteroids” where we had to avoid the ice blocks and flows that moved towards us swiftly. We managed to get passed the island and up onto the sill, and successfully map across from the island to the northern shore of Bessel Fjord. It was much shallower than expected! The deepest point we crossed was only 15 m, but the main cross section was generally shallower than 10 m. To take a big ship like Oden drafting 8 m across this sill would likely have ended in a disaster! The first part of the Bessel Fjord mission was completed; we now know that a big ship cannot just enter the fjord and take sediment cores!

After the fjord sill was investigated we mapped the outside of the fjord entrance to look for signs of an ice stream that at one time may have flowed out from Bessel Fjord. The mapping went superbly well, although there were no direct signs of ice streams imprinted in the seafloor. However, the seafloor is so extremely scoured in this area that old traces may also have been erased. The finale consisted of a nearly complete mapping around a grounded piece of the ice shelf that broke off from the Petermann Glacier August 2 and had run aground outside of Bessel Fjord. The mapping allowed us to measure the ice shelf draft and get a fresh image of a large iceberg scour in the seafloor. What a superb ending to a spectacular day!

Bessel Fjord entrance. Skidbladner is seen in the middle of the view mapping in front of the ice blocking the inner end of the sill . This is inside of the moraine island at the fjord entrance. Photo: Johan Baalack, GoPro mounted underneath Helicopter

The Skidbladner crew from left to right: Mikael Molin (Scientific Technician, Swedish Polar Research Secretariat), Larry Mayer (Professor, Center for Coastal and Ocean Mapping, University of New Hampshire), Kelly Hogan Pires de Matos (British Antarctic Survey). 3D-view of the collected bathymetric data outside of the Bessel Fjord entrance. The 400 m long ice shelf berg grounded on the bottom after producing a ca 3 m deep plow mark. We were able to map around the iceberg by us passing very close with Skidbladner such that the multibeam could reach and map the iceberg sides.

A corner of the mapped shelf iceberg that originates from Petermann Glacier.

Oden waiting for us coming back and be picked up after a long successful day of mapping.

Skidbladner returning to home base Oden. Photo: Björn Eriksson

 Mapping the environment underneath an ice shelf

An ice shelf is a floating glacier. Most ice shelves are formed as extensions of one or several ice streams that drain glaciers and large ice sheets by transporting ice to the ocean. The ice shelf begins from where the ice stream lifts from the bed and becomes afloat. The zone where this lifting occurs is called the grounding line, or more accurately, the grounding zone as it occurs over an area rather than one specific line. Seaward from the grounding line, the ice shelf typically thins until it becomes sufficiently fragile to break and form icebergs. This is called calving and the thinning is due to the mechanics of ice. Two main mechanisms can influence the ice shelf thickness; 1) freezing underneath the ice shelf may occur which thickens it and, 2) warmer water may interact with the ice shelf’s underside and instead accelerate the thinning substantially. The latter is what has been found to happen with the Petermann Glacier ice shelf. Andreas Muenchow is a physical oceanographer from University of Delaware who has worked specifically with the oceanography of the Nares Strait, the body of water that separates Greenland and Canada. He has studied the interaction between warmer water of Atlantic origin and the Petermann Glacier. Over the last years, there has been a clear warming, although the series of existing oceanographic measurements are too short and do not provide sufficient spatial coverage to fully conclude what is happening. Therefore, Andreas’ main goal during our expedition is to collect CTD (Conductivity, Temperature, Depth) measurements along strategically placed transects in the Petermann Fjord area.

The under-ice shelf environment is poorly known, in fact one of the least know ocean environments on Earth. We do not know much about the life underneath ice shelves nor the sedimentation that occurs there. We have now managed to completely map the seafloor in the Petermann Fjord with Oden in front of the ice shelf and cross over the sill, which is the shallow part that separates the outer Nares Strait from the inner deep Petermann Fjord. The seafloor morphology clearly reveals that the Petermann Glacier in the past extended all the way out and across the sill and flowed northward into Nares Strait. We also took several sediment cores in the fjord where there use to be an ice shelf. This means that we have captured the under-ice shelf environment as recorded by the accumulated sediments. Andreas collected a CTD transect from the sill to the shelf edge. We enjoyed ice free conditions in the fjord for a couple of days, then the wind changed and ice begun flowing back again. In fact, not too bad since we then could go out and concentrate on the sill which is critical for us to fully map and core. The part of the Petermann Ice Shelf that calved when we just arrived has now floated out towards the fjord sill. We steamed up just close to it several time, even if the ice shelf is rather thin at the front.
The mammal observer has spotted many seals in the Petermann Fjord. She finds an interesting spatial pattern where the seals, specifically ring seals, hang out in front of the small outlet glaciers that drain ice from the surrounding high mountain glaciers along the sides of the fjord. In turn, this correlates with our sonar data showing plumes of sediments originating from sediment laden meltwater from these glaciers. Like on some many previous expeditions, it can be very productive to view scientific problems from many different disciplines, and an expedition is one of the absolute best places to bring scientist with different backgrounds together.


Left: Different locations of the Petermann Ice Shelf front. The bright green line from 2010-07-22 shows the extension of the ice shelf some weeks before the main break off event in mid-August. The purple circles show our sediment core locations and the black circles with green crosses oceanographic CTD-stations. Right: The multibeam echo sounding mapping completed with Oden inside the Petermann Fjord. The data shows a suite of charactersistic landforms that will help us interpret the Petermann Glacier’s history.

Oden in the middle of the Petermann Fjord. A part of the ice shelf that broke off August 2 is seen in the left of the photo. In the far back, the Petermann Ice Shelf is seen.

Mountains on the Canadian side of Nares Strait south of Hans Island.

Oden in front of Petermann Ice Shelf.

 Breaking into Petermann Glacier

After passing the sea-ice clogged passage at the southern end of Nares Strait, the transit to Petermann Fjord went quite fast. We had excellent support from the satellite images sent to us by the Polar Geospatial Center at the University of Minnesota. The transit was also facilitated by continuous sea ice reconnaissance flights with the helicopters. It became one of my duties to go with our Captain Mattias in the helicopter and place waypoints and record the flight tracks with my GPS. Back on the ship, I brought all GPS information into mapping software and made route plans. This process has to flow very fast; directly from the helicopter to the computer and make a map!

Along our way we dropped off barrels with fuel at two locations on the Greenland coast. The fuel was brought to land as sling loads hanging below the helicopter. Our pilots Sven and Johan have a lot of cold weather flying experience which is essential to fly in Arctic conditions. I met Sven for the first time 2004 when he was the helicopter pilot during the Arctic Coring Expedition (ACEX) in the central Arctic Ocean. Since he has been on numerous Arctic expeditions, I suspect that only few in the world have the same high Arctic flying experience as Sven.

When arrived to the entrance to Petermann Fjord August 3 it was blocked by sea ice, a new ice breaking challenge for Mattias and his crew and more helicopter flights. The southerly wind that prevailed for many days had pushed sea ice up against Hall Land in the north. Once we reached the location where the sea ice was pushed together, we decided to begin by mapping just south of it as it belongs to our main research area.

The scenery was simply spectacular. The high nearly vertical mountain walls along the fjord sides are dramatic to say the least.

It was some work to break through the sea ice at the fjord entrance, but well inside, the area in front of the Petermann Ice Shelf was completely clear. Finally, we could begin map our main target area! This area was before the two big calving events 2010 and 2012 covered by the Petermann Ice Shelf. It means that we have a unique opportunity to map and take sediment cores in an area that use to be underneath an ice shelf. We are the first to be able to do this in the Petermann Fjord. One of our main goals with the entire expedition is to study the environment underneath an ice shelf. In particular since the Petermann Ice Shelf has thinned over the last decade. To complement our marine work, we have a team that will drill through the Petermann Ice Shelf from Brittish Antarctic Survey (BAS). Next challenge is to fly them to their drill sites on the glacier including their drilling equipment which amounts to more than 13 tons!

Just when we entered the fjord, new reports came in that a rather large piece of the ice shelf calved. This was clearly seen on satellite images. The section that broke off was a bit wider than 3 km, so tiny in comparison to the previous calving events 2010 and 2012.

  Oden at the entrance of the Petermann Fjord

Landsat satellite images showing the Petermann Glacier and the main calving events 2010 and 2012 as well as small calving 2015 that occurred just when we entered the fjord with Oden.

 Drilling camp, Brittish Antarctic Survey (BAS). Photo: Markus Karasti


Photo: Markus Karasti

 Breaking through the sea-ice bottle neck of Nares Strait

After leaving Thule we had a smooth ride up to Smith Sound in Nares Strait where sea ice clogged the entire passage northward. This happened somewhere around 78°30’N. Every winter Nares Strait fills up with sea ice that forms a quite solid “ice-bridge” between Ellesmere Island in the west and Greenland in the east. The strait usually clears from sea ice sometime in July, but the break-up is late this year. It has not even cleared in the moment of writing, August 2. This means that we have to break through the sea ice that is blocking us from reaching the working area for the expedition, the Petermann Fjord and adjacent areas all the way across to Ellesmere Island on the Canadian side.

Even if Oden is one of the most capable icebreakers in the world, it proved very difficult to break through the bottle neck where sea ice had piled up. This was due to that the ice has been pushed together so that thick ridges formed between solid flows. Adding fog on top, the situation did first not look good at all. Our captain Mattias decided to stop for a while and wait for the fog to clear, because breaking blindly into walls of sea ice ridges did not make us progress much at all. During the morning, the fog cleared so we could fly with the helicopters and make some sea-ice reconnaissance. We also received SAR (Satellite Radar Aperture) and Landsat images from Polar Geospatial Center at the University of Minnesota. These images were extremely helpful as they give a fresh broad overview of the ice situation. From these images we planned the helicopter flights. After about five helicopter flights to find good paths for Oden we were through the bottle neck. We shall now see how the sea ice situation evolves during our transit up to the Petermann Glacier where the first thing on the list to do is to helicopter all teams that will work on land. More about these later!

 

Polar bear close to the Oden.

Oden after passing through a difficult stretch of sea ice.

The sea ice from above. This photo is taken north of the really difficult passage where there were good passages between larger flows.

 From Kangerlussuaq to Thule

After two nights in Kangerlussuaq I think we know the town. But we certainly do not know the amazing surrounding nature! It is rather spectacular, specifically close to the nearby glacier that contains an ice stream that transports ice from the Greenland Ice Sheet to the ocean. There is an approximately 25 km long road from Kangerlussuaq to this glacier. It was built by Volkswagen because they needed a remote dirt road to test their cars. This road also makes it possible to bike all the way to the glacier, a dream for geologists, such as myself, who get a kick out of watching how landforms are produced by an active glacier. The glacier does not end up in the ocean since it has retreated up on land. It means that no icebergs are produced from this glacier. Instead, it loses mass in the summer time by melting. Meltwater is flowing from the glacier and forms a river system that passes Kangerlussuaq before ending in the ocean. There is an enormous amount of sediment carried by the meltwater which makes the water color vary a lot. Sometimes a melt pond can be turquoise while nearby flowing water can be brown.

Houses in front of the glacier near Kangerlussuaq.

Muskoxen are very common around here. This is clearly seen on the local menus of the two only existing restaurants in Kangerlussuaq. My first dinner here was a muskox burger, actually not bad at all.

Muskoxen.

The glacier near Kangerlussuaq.

The glacier near Kangerlussuaq.

Discussions in front of the science facility in Kangerlussiaq

The second morning after we arrived it was time to move on and fly with an American C130 to Thule, little less than three hours long. Before we left I checked the latest satellite images of the Petermann Glacier area. Not quite as good as we had hoped for. The sea ice break-up in Nares Strait is at least one week delayed compared to the most recent years. There is a quite dense clog of sea ice in the lower part of the strait which we will have to break through if nothing changes over the next upcoming days. The wind has been from south so sea ice have been pushed back up into the Nares Strait instead of draining out to face a certain death through melting in Baffin Bay. Once we get to Nares Strait, we will see how close the satellite images reveal the true nature of the sea ice!

The US Air Force C130 that flew us up to Thule.

 The day before departure to Greenland

Today Sunday 26 July, Swedish Icebreaker Oden steamed into the fjord where Thule Air Base is located on northwestern Greenland. This completes an 18 days long journey from southwestern Sweden to Thule. We have designed Oden’s route across the Atlantic and along the Greenland west coast specifically to collect new depth measurements of unmapped parts of the seafloor with the installed multibeam echo sounder. I can see from the online tracker built by Rezwann Mohammad that Captain Eric Andersson and crew did an exceptionally good job of following our proposed route! It feels almost like we are spying: http://oden.geo.su.se/map 

The goal with this route is to complement the depth database of the International Bathymetric Chart of the Arctic Ocean (IBCAO) and to contribute to the new NASA research program “Ocean Melting Greenland”, which focuses on the interaction between the ocean and the Greenland Ice Sheet through all so called outlet glaciers (http://www.iarpccollaborations.org/news/1556) . PhD student Francis Freire from the Department of Geological Sciences has been onboard to see that the multibeam echo sounder is working continuously and that is it regularly calibrated with sound speed measurements of the ocean water. Francis also operates the installed chirp sub-bottom profiler, collecting information about the uppermost 50200 m of bottom sediments, and the mid-water sonar, which provides information about the water structure and marine life such as fish and plankton.

All of the scientific crew that will take part in the Petermann Glacier 2015 expedition will travel to Greenland tomorrow in order to meet up with Oden in Thule. We will first go to Kangerlussuaq with a regular Air Greenland flight from Copenhagen and from there fly with an American Air Force plane to Thule.

During the last days I have monitored the sea ice situation in the Petermann fjord intensively. Nares Strait separates Greenland from Ellesmere Island. The strait and all connected fjords fill up with dense sea ice every year during winter. The sea ice becomes land fast and difficult to penetrate even for the strongest ice breakers. Practically every summer, the Nares Strait clears out from most of the sea ice. Andreas Muenchow from University of Delaware is an oceanographer that spent a lot of time studying the Nares Strait region and the oceanography of the Petermann Fjord area. Andres has written a very nice explanation on how the sea ice dynamics in the Nares Strait works: http://icyseas.org/2015/07/13/oceanography-of-nares-strait-ice-flushing 

The flushing of sea ice from Nares Strait has come late this year, but during the last week we have seen a lot of sea ice movement in the area which is promising for our expedition!

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