Category Archives: Petermann Glacier

Petermann Ice Island 2012 Breaking Up

Posted on September 2, 2012 by | 5 comments

Dr. Preben Gudmandsen pioneered some of the early micro-wave remote sensors 30-40 years ago that are now used routinely to monitor sea ice, snow, and glaciers. Despite being “retired” for over 20 years, this Danish professor of Electrical Engineering is still very active in all things related to Nares Strait from sea ice, oceanography, glaciers, and winds. He is one of the main instigators to set up the automated weather station at Hans Island.

Nares Strait bottom depth (in meters) according to the International Bathymetric Chart of the Arctic Ocean (IBCAO, version 2, 2008). The black dot in the center of Nares Strait indicates Hans Island.

He also instigated the latest round of exchanges among “Friends of Nares Strait” about the fate of the ice island that broke off earlier this summer from Petermann Gletscher. He asked yesterday what may happen if PII-2012 reaches the sill separating northern Nares Strait and the Arctic Ocean from southern Nares Strait and the Atlantic Ocean. This sill is the deepest connection between the Arctic Ocean to the north and Baffin Bay in the south. The sill is in western Kane Basin off Ellesmere island and is about 220 meters deep.

So, to answer that question one needs to know three things: Where is the ice island, how deep is the water where it is, and how thick is the ice island. Before I could assemble these three things, however, the ice island has already broken into at least three pieces. Luc Desjardins of the Canadian Ice Service answered first by pointing this out. He has access to the commercial RadarSat data that few others have. So, here is the latest from MODIS which answers the first two questions:

Petermann ice island 2012 (PII-2012) breaking apart on Sept.-1, 2012 near the sill of Nares Strait. Faint black lines are bottom contours of 200, 150, 100, and 50 meter depth (IBCAO-2). Bottom left has clouds, top right is the mountainous terrain of Ellesmere Island. The most southerly part of PII-2012 is the thickest as it was attached to the glacier earlier this year. The most northerly section connected to PII-2010 which passed a moored array in place near Hans Island on Sept.-22, 2010.

Petermann Ice Island 2012 as one piece on Aug.-30, 2012 19:20 UTC in Kane Basin over contours of bottom topography.

From the above two MODIS images over contours of bottom topography, the shallowest water that PII-2012 has seen is the 150-m contour to the east towards Greenland. It is possible, however, that PII-2012 may also have hit some shallow topographic feature not properly charted in IBCAO-2008 (there is a 2012 version, I just learnt) or not properly contoured by me. Lets move on the next question, how thick is this ice island?

From data we recovered 3 weeks ago I can say, however, that PII-2012 is thicker than 144 meters. I base this estimate on the ice island that formed in 2010 and that passed over our moored array on Sept.-22, 2010. It hit two ice profiling sonars at 75 meters and damaged the stainless steel guard cage designed to protect the sensors (which they did), e.g.,

Two Ice Profiling Sonars (IPS) aboard the CCGS Henry Larsen in Aug.-2012. The bent stainless steel protective frame was bent by the 2010 ice island that hit both instruments in Sept.-2010. [Photo Credit: Andreas Muenchow]

Another instrument moored deeper at ~360 meter depth sends out acoustic pings and measures how much sound comes back. A weak scatter like some microscopic plankton or grain of mud or sand in the water reflects little energy, but a hard surface like the ice floating atop reflects lots. And here is how a time series of this backscattered energy looks like when an ice island passes over:

A 24-hour segment of acoustic backscatter from a bottom-mounted acoustic Doppler current profiler is show to vary with time and height above the bottom. The dark red represents the sea surface and/or the bottom of ice floating on it. Vertical resolution is 8 meters, temporal resolution is 30 minutes for a 3-year deployment. The main purpose of this instrument is to measure ocean currents at the same spatial and temporal resolution as shown here for backscatter. PII-2012-B passed over the instrument on Sept.-22, 2010 and is here estimated to be about 144 meters thick.

The exact place of the mooring and the time that PII-2010-B was on Sept.-22, 2010 is shown in this MODIS image of that day:

Location of ADCP mooring site (red square) with Petermann Ice Island 2010 segment B overhead on Sept.-22, 2010.

If you like puzzles, then you will like physical oceanography or any field of science or engineering. If you like puzzles, you will correctly notice, that the flat segment of PII-2010-B oriented parallel to the shores of Ellesmere Island fits the flat segment of PII-2012 that also has a hook to the north. These two segments were indeed connected before they separated from the glacier in 2010 and 2012. This is the reason, that the thickest part of the 2010 ice island is the shallowest part of the 2012 ice island, because the ice gets thicker towards the grounding line of Petermann Gletscher.

And finally, if you like puzzles, then you should consider a career in physical oceanography or physics or mathematics or electrical or mechanical or civil engineering. These are fields where jobs and careers are plentiful and people live long and happy lives: Preben chose Electrical Engineering 70 years ago in Denmark, I chose physical oceanography 30 years ago in Germany, and Allison chose physics 3 years ago in the U.S. of A. Sadly, few American students chose to compete for these jobs and lives, because they need to take a “difficult” undergraduate major. Allison did, she picked physics and oceanography, and so can you.

University of Delaware summer intern Allison Einolf from Macalester College, Minnesota in Nares Strait in Aug.-2012 aboard CCGS Henry Larsen. Allison studies physics. [Photo Credit: Jo Poole, British Columbia]

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Arctic Ice Cover and Petermann Fjord, Glacier, and Ice Island Video Footage

Posted on August 27, 2012 by | 2 comments

The National Snow and Ice Data Center announced today, that the Arctic Ice Area Extent has reached an absolute minimum breaking the record minimum of 2007 with still several weeks of potential melting and retreat to go. This has been anticipated for many weeks now with perhaps the most extensive coverage and intelligent discussions over at Neven’s Arctic Sea Ice Blog.

The graph above shows Arctic sea ice extent as of August 26, 2012, along with daily ice extent data for 2007, the previous record low year, and 1980, the record high year. 2012 is shown in blue, 2007 in green, and 1980 in orange. The 1979 to 2000 average is in dark gray. The gray area around this average line shows the two standard deviation range of the data. The 1981 to 2010 average is in sky blue. Sea Ice Index data. [Credit: National Snow and Ice Data Center]

This is as big a deal, because an ice-covered ocean reflects much more sunlight back into space in summer than a black ocean does that absorbs more heat: a positive feedback. This is why people in hot climates wear white, not black clothes, they like to stay cool. Furthermore, this decline has been ongoing for the last 30 years and the climate models that policy makers rely on did not predict this level of ice cover to occur for another 20-30 years. So, the warming climate and the changes it caused are on an accelerated schedule with regard to the Arctic Sea Ice cover. Also, the remaining ice cover is thinner than it used to be, because the multi-year ice keeps leaving the Arctic faster than it can be formed inside the Arctic. Both the Fram Strait to the east of Greenland and Nares Strait to the west of Greenland export this old, hard, and thick ice that ultimately melts further south. The ice that is left in the Arctic Ocean has become both thinner, younger, and softer, making it easier to melt the next summer.

On somewhat related news from the University of Delaware (UDel), we put two videos together that show a tiny, if spectacular example of a different area that has never been ice-free for at least 150 years when people were looking: Petermann Fjord. On August 10/11, 2012 the Captain and crew of the Canadian Coast Ship Henry Larsen gave us unfettered 18 hours access to the newly ice-free waters of this large glacier that discharges about 6% of the Greenland ice sheet. The UDel press release has the video that is also posted at youtube. As a less professionally assembled version is my first introductory iMovie project, e.g.,

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Posted in Global Warming, Ice Cover, Ice Island, Nares Strait 2012, Petermann Glacier

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New Ocean Observations in Petermann Fjord

Posted on August 22, 2012 by | 10 comments

A new ice island separated from Petermann Glacier on July 16, 2012 as reported here first. Less than 4 weeks later, the Canadian Coast Guard Ship Henry Larsen reconnoitered the ice island on Aug.-9 when it blocked the northern half of the entrance of the fjord.

Petermann Ice Island 2012 (PII-2012) as seen Aug.-11, 2012 at the entrance of Petermann Fjord. The view is to the north-west. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

I was aboard this ship when Captain Wayne Duffett decide to break into the largely ice-free fjord behind the ice-island after consultations with Ice Services Specialist Erin Clarke. The ice observer had just returned from her second helicopter survey in 2 days with pilot Don Dobbin to assess both ice cover and its time rate of change. From the time the ship entered the fjord behind the ice island, hourly flights to a fixed point at the south-western corner of the ice island ensured that its movement would not cut off the ship’s exit. This approach worked and it gave the science crew of 8 aboard about 18 hours to conduct the very first survey of a previously ice-covered ocean:

Petermann Glacier, Fjord, and Ice Island as seen by MODIS at 865 nm on Aug. 07, 2012 overlaid with survey lines of CCGS Henry Larsen on Aug.-9/10/11, 2012 in red.

We were not funded to do enter the fjord, but our main mission to recover an array of ocean moorings with 3-year long data records covering the 2009-12 period about 100 km to the south in Nares Strait has already been accomplished. So, what does a physical oceanographer do when in uncharted and unknown territory? He drops a number of CTDs, that is, measuring conductivity (C), temperature (T), and depth (D, pressure, really) as the instrument (the CTD) is lowered at a constant rate from the surface to the bottom of the ocean at a number of stations. The results from such work next to the present front of Petermann Glacier was a surprise for which we do not yet have a satisfactory explanation: The waters inside the fjord are much warmer at salinities 32.5-34.25 than they are outside the fjord:

Temperature as a function of salinity from 9 stations across Petermann Fjord next to the current seaward edge of Petermann Glacier on Aug.-10, 2012 in red. For comparison I show in blue a station done outside the fjord on Aug.-9, 2012. Note that temperatures increase with increasing salinity which is expected for waters that are a mixture of cold and fresh polar and saltier and warmer Atlantic waters. Density deviations from 1000 kg/m^3 are shown as solid contours along with the freezing temperature that decreases with increasing salinity.

Another way to show the same data is to actually plot the section, that is, the distribution of temperature and salinity in physical space across the fjord as a function of depth:

Section across the seaward edge Petermann Glacier on Aug.-10, 2012 for salinity (left panel) and temperature (right panel). Symbols indicate station locations from which color contours are drawn. Note that the display is cropped to the top 300 meters while real recordings extend to the bottom which exceeds 1000 meters. The view is eastward towards the glacier with north to the left.

Note the doming salinity contours which to classically trained oceanographers suggest a flow out of the page on the right and into the page on left with maximum at about 90 meter depth relative to no flow at, say, 500 meter depth. Another way to view this distinct property distribution is that the flow above 90 meters is clockwise (outflow on left, inflow on right) relative to the more counter-clockwise flow below this depth. This feature, too, comes as a surprise and requires more thought and analyses to explain.

There is much more work to be done to figure out what all this means. I feel like scratching the surface of a large iceberg half-blind. The data from below 300 meter depth, too, contain clues on how some this glacier interacts with the ocean. As for the purpose of this post, I merely wanted to report that the ice island is presently having a hitting or scratching tiny Hans Island. The latter is unlikely to move, but Petermann’s Ice Island will slow on impact, swivel counter-clockwise, bump into Ellesmere, and pretend nothing has happened on its merry way south. This is the latest image I have:

Petermann Ice Island 2012 on Aug.-22, 2012 as seen by MODIS Terra at 21:45 UTC. The tiny red dot marks Hans Island, the location of a weather station in the Kennedy Channel section of Nares Strait. Petermann Fjord is towards the top right out of view.

ADDENDUM Sept.-1, 2012: PII-2010B had a maximum thickness of at least 144 meters as it passed over a mooring that measures ocean currents from the Doppler shift of acoustic backscatter that is shown here for one of four beams:

Time-depth series of acoustic scatter from a bottom-mounted acoustic Doppler current profiler for 24 hours starting Sept-22, 2010 9:30 UTC. Red colors indicate high backscatter from a “hard” surface like ice. The vertical axis depth in meters above the transducers while the horizontal is ensemble number into the record (0.5 hours between ensembles). The 2010 ice island from Petermann Glacier (PII-2010B) passed over the mooring. When PII-2010B was attached to the glacier it was adjacent to the segment that became PII-2012 this year.

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Nares Strait 2012: First Petermann Ice Island Photos

Posted on August 17, 2012 by | 1 comment

The CCGS Henry Larsen dropped its science party of nine at Resolute on Cornwallis Island near the center of Lancaster Sound. We are staying at the “Polar Continental Shelf Project” which is a Government Canada base for science and logistics people working all over the Canadian High Arctic. Over dinner we met a group of graduate students, botanists, whom we had met 4 days ago at Alexandra Fjord where they were living since June. I had missed the rendezvous on the water then, because I freakishly tried to refurbish a tide gauge that we recovered in the morning and re-deployed in the afternoon. One of the students, Anne, told Renske and me, that they saw narwhales at Alexandra Fjord for the first time in at least 4 summers that she lived there. I wonder, if those were the same narwhales that we Petermann Fjord.

North-eastern portion of Petermann Glacier on Aug.-11, 2012, the meandering river is the centerline, view is almost due east. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

Which brings me to the purpose of this quick blog entry: The Internet on land, while not much faster than on the ship, is more stable. This allowed me to download the first photos of both the ice island at the entrances of Petermann Fjord and the new front of the glacier far into the fjord. The pictures were taken from the helicopter checking on the ice island last Friday as we worked sections deep inside the fjord. It was a frantic day of data collection in stunned scenery. It was challenging to stay focused on keeping sensors, computers, and winches running smoothly with so much natural beauty in all directions. I will post more photos in higher resolution as soon as we are getting home late sunday night. As a first teaser, however, here the first of many photos and videos. The two photos below I degraded from 4-6 MB to 0.1-0.2 MB to allow for limited bandwidth up north.

Petermann Ice Island 2012 (PII-2012) as seen Aug.-11, 2012 at the entrance of Petermann Fjord. The view is to the north-west. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

Addendum: Last night I uploaded the 4.6 MB version of the image. Photo credit should again be given to Canadian Coast Guard Ship Henry Larsen, it was Jo Poole of British Columbia who took the picture using the official ship’s camera. Leaving for Iqualuit in 3 hours.

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Nares Strait 2012: Renske’s Blog on Data Collection (and other adventures)

Posted on August 14, 2012 by | 2 comments

Dr. Renske Gelderloos, from Oxford University, has posted more accounts of data collection from the CCGS Larsen (including a description of rosette operations by our own Pat Ryan).  Read her copied posts below, or follow her accounts at her blog directly (where there are additional photos from the area, taken in 2009).

CTD sections…

7/8 August 2012:

Two days of CTD sections. We actually need to work on the weather stations as well: there is a weather station on Cape Baird that needs to be dismantled and relocated to Joe Island on the other side of Nares Strait. Access to a weather station, however, requires a helicopter and the weather has changed from its lovely sunny side to a cloudy and windy variety. There is either far too much wind for the helicopter to fly, or it is foggy and then we can’t fly either. The main activities are therefore centered around taking CTD profiles, which, by the lack of other activities and the need for a deck crew for the rosette system, is now a daytime activity. We take one section just south of Petermann Fjord, and one further north in Robeson Channel. The latter section is extra nice because this part of Nares Strait was often too much ice covered to access for taking measurements in previous years.

In the late afternoon of 8 August the FRC (the small boat) is sent out into Discovery Bay to try and recover a tide gauge pressure mooring that had been there since 2003. In that year, a diver from the American ship ‘Healy’ installed this mooring. In 2006, when the first next ship for scientific purposes came up here, the bay could not be reached because of heavy ice conditions. In 2007, during the expedition thereafter, the science crew flew to the bay by helicopter and successfully talked to the mooring and released it, but it has never come to the surface. In 2009, on the third expedition after deployment, heavy ice conditions again inhibited access to the bay. Now, in 2012, we decided to take the absolute longest of long shots in trying and recover this mooring (if the bay would not be frozen over) using a sinking line and try and ‘catch’ the mooring. As we knew the exact location, it was at least worth trying. So, the FRC was sent into Discovery Bay and came back later that evening, to everyone’s astonishment, with the mooring on board that had been happily recording data for the full nine years it had been there in the water! (In an attempt to be creative I naively inquired whether it would be an option to land the FRC on the beach below Cape Baird and walk to the weather station. Given the steep slope and significant height of the plateau, this idea was quickly discarded.) The success with the Discovery Bay mooring was later celebrated at the bar.

…and water sample collection

During some of the CTD profiles we also take water samples. As I am in the ‘CTD command centre’ almost full time during the sections, I asked Pat Ryan to write something about the water sampling. Here is her story:

Water Sample Collection, by Pat Ryan, University of Delaware

One of the ways oceanographers study the sea is through the collection of water samples.  Chemical oceanographers evaluate the characteristics of water to provide information on the source of the water, contaminants and conditions of the sea to sustain life among other things.

The collection of water aboard the Larsen is done in a contraption we call a rosette.  It’s comprised of a number of Niskin bottles (large cylindrical plastic bottles), in our case 12, held upright in a large round metal frame.  Our rosette is about as tall as I am (170 cm).  As the device is lowered into the ocean, all of the bottles are open at both the top and the bottom so that there are more cylinders than bottles. As the rosette is lowered, water flows freely through the open bottles as if they were pipes… stoppers at each end are connected to a tension-based triggering device that can close both ends instantaneously – thereby capturing the seawater residing at the depth of the rosette at the time of firing.  On the deck, connected via wire to the rosette, is a computer that sends a signal to each of the bottles when the operator wants to capture water.

Our rosette is typically lowered at a controlled rate to the bottom of Nares Strait collecting samples on its descent and then quickly brought back up.  Attached to the rosette is also a CTD device that continuously provides salinity, temperature and depth information to the operator.  Physical oceanographers use these data to analyze aspects of the sea and for the water collection purpose this information is vital to collect samples (that is to trigger the closure of bottles) at specific depths.

All of the heavy work of wrangling the rosette off and then back onto the deck of the ship is done by the deck crew of the Henry Larsen.  Garbed in bright orange jumpsuits and hard hats, the crew pilot the heavy and cumbersome rosette to a gentle landing after each cast.  They are a great group of guys who regale us with tales of the sea, and places back home (Newfoundland for most of them) and make us laugh to the point that we sometimes even forget how cold our hands are!

While the deck crew is managing the heavy work of the rosette, one of the science team members, Jo, mans the winch, hoisting, lowering and then raising the rosette up as directed by another member of our team, Renske.  She operates the computer, carefully monitoring the graphics which tell her where the rosette is at all times.  It’s Renske who determines when each of the bottles fire.

As soon as the rosette is safely back aboard, the piddlers get to work.  We are members of the science crew assigned to get the samples from each Niskin bottle into the pre-labeled sample bottles.  First, we check that the bottles have fired properly and that there are no signs of leaks that would indicate a sample was compromised.  Then a group of us (3 is a nice number – as it speeds up the process and is not so many that there are traffic jams on the deck) set about the task of filling various glass and plastic vials with very cold ocean water, these will be shipped to a lab for analysis when we port.  The label in each bottle indicates the location and depth at which the sample was collected as well as which type of analysis is to be performed.  On this trip we are sampling for O-18, Barium, Salinity and Nutrients.   Protocols to insure the integrity of the sample for each analysis are followed – some of the samples must be immediately frozen and kept at very cold temperatures.  Others require specialized gaskets to prevent oxygen transfer.  Duplication of some samples provides for quality control check performance.   Every time the rosette is deployed, we typically fill about 50 bottles.  Each of the bottles is rinsed with the sample several times prior to being filled – as we dump this rinse water onto the deck, this process can lead to wet shoes and socks when the wind is blowing hard as it was yesterday. In the Arctic, this water piddling as it is “affectionately” dubbed can be chilly, wet work.  Your hands can feel like you might not get sensation back for days and on a windy day (as we had yesterday) the water can be blowing in sheets to soak you.

That being said, it can also be an enjoyable group endeavor.  Our lead scientist often joins us filling bottles and Renske will lend a hand as time permits.  There is a frenzy of activity when the rosette alights upon the deck that feels like work but the camaraderie of the piddlers and the tendency to easy laughter among the group actually makes it some of the fondest (if perhaps coldest) memories of my Arctic experience.

An Arctic Hike

9 August 2012

When I woke up this morning, the wind had not settled down. Quite the opposite to be honest: For the first time since we left Thule the boat was significantly moving in other directions than forward. Taking the helicopter to Cape Baird was absolutely out of the question, and the usual 8-o’clock science meeting was cancelled because it did not seem we would be able to do anything in this weather.

I took a cup of coffee to my cabin and wrote a bit on this blog. After finishing I decided to go up to the bridge to get the latest info on the state of affairs. At the bridge it turned out that the idea to take the FRC to shore and climb up the cliff was being considered more seriously. Apparently, something that is considered impossible one day is suddenly not such a bad idea the next one out here. I was asked to come along and immediately agreed! I knew it would be a tough climb and a windy exercise on the plateau, but this unique opportunity to walk up a glacial outlet and be part of this, admittedly, somewhat absurd plan, I did not want to miss for the world. The carefully-put-together list of absolute essentials to dismantle a weather station was, figuratively speaking, thrown overboard and replaced by a light-weights-only list, as we would have to carry everything up the hill. The magnitude of the team was now determined by the number of people required to carry tools up the hill and tools and a dismantled weather station down the hill. The science team was therefore expanded to four (Humfrey, Dave, Andreas and me) and a crew member with a shotgun (Melvin) was added to the team in case of a polar bear attack. Chief officer Brian, aided by seaman Derick, skillfully maneuvered the FRC from the ship to the beach below the cliffs (while making sure we all got absolutely soaked were it not for our waterproof floater suits),  where we jumped out of the boat onto the beach with our backpacks.

From the beach the least steep route (but still steep) to the plateau where the weather station was situated was through a dry glacial valley. The ground was covered in loose gravel and stones, which made the climb up not an easy hike. In some less covered spots small mosses and tiny plants had been able to find a habitat to flourish, really amazing! I am not a biologist and know little about plants, but this surely is not an easy environment for most life I know. Humfrey later explained that some of the plants we had seen were actually even tiny trees. While sliding backwards we made progress upwards (being Dutch I am not really used to steep slopes anyway) and finally the weather station came into sight. The wind conditions up here were far from ideal to do anything at all! Wind gusts down at the ship reached well over 30 knots, up here they were a lot more severe. We had to strongly lean into the wind and secure everything we laid on the ground with heavy rocks to prevent them from being blown away. Some of the dismantling had already been done for us by local animals (one of the damaged items was definitely the work of a polar bear; cut wires could have been done by other animals). We wrapped the sensors in bubble wrap and put them in my backpack. The tools went back into other backpacks and the battery box and the solar panel had to be carried down while holding them in our hands. Humfrey decided we would take the short way back, which meant sliding down the steep side of the hill straight to the beach. Being only a little over sixty kilos, and very aware of the insanely expensive equipment on my back, the combination of this route and the wind made me go down very slowly. We all made it down to the beach safely, and quickly afterwards Brian and Derick came to pick us up. With a tail wind the ride back to the ship was a lot more comfortable than the way out. Time for a shower and some laundry…

First sight of the Petermann ice island

9 August

Ever since a large piece of the glacier tongue of Petermann Glacier broke off on the 22nd of July (now commonly referred to as ‘the ice island’), we have been anxiously monitoring the movement of this island. The event gives us both opportunities and threats: We are studying the ocean circulation (and its effect on glacial melting) in this fjord. This piece of the glacier breaking off may give us the opportunity to take measurements in a previously covered and therefore inaccessible area. The last time a ship went here to take measurements was in 2009, and incidentally two large calving events have taken place since then (the first one being in August 2010), so really a large part of the fjord that was previously covered under ice is now accessible by ship. On the other hand, the island can block the entrance to the fjord altogether and we may not be able to get in at all.

We are close to the ice island now and are very curious to see it. The news of the piece breaking off made the TV news all over the world, but we are probably the first people to see the island in real life. The captain announces this long awaited moment by: “All ship personnel, all ship personnel; there is a little piece of ice next to the ship if you’re interested”. The bow quickly crowded with people with cameras taking lots of pictures. By the time this ice island will reach the more inhabited part of the world (say Newfoundland) it will have been broken into smaller pieces and not be so gigantic anymore.

This ice island breaking off of the ice tongue of Petermann Glacier is not necessarily a dramatic and life changing event. This glacier tongue loses 80 to 90% of its ice through melting from below, because the ocean water is relatively very warm (don’t get too excited now, it is only about 0.2 degrees Celsius so not particularly hot-tub temperatures). Calving of ice from the edge is only responsible for a tiny fraction of the total ice loss. That being said, if the glacier continues to calve off ice, this may be different in the future.

After the ice-island sight-seeing moment it was time for dinner (or ‘supper’ as it is called on the ship). Supper time is quite early, from 16.30 h to 17.30 h. Chief scientist Humfrey decided on a night-time CTD section (up to about midnight) in the alongside direction of the fjord, away from the ice island and away from the fjord. Tomorrow we will see whether we can go into the fjord and do the rest of this section and another one. Things don’t look good though: the ice island is completely blocking the northeast side of the entrance, while the southwest side is stuffed with thick multi-year ice. But first to bed, and we will see what happens in the morning.

Data collection in Petermann Fjord

10 August 2012

After a short night I woke up this morning for regular breakfast hours between 7 and 8 am. It became clear that we would not be taking measurements in at least the next few hours, so I took the opportunity to catch up on some sleep. After about two hours I was woken up in a not-so-gently manner by the ship’s crushing the thick multi-year ice in the southwestern part of the Petermann Fjord entrance. After an ice reconnaissance flight by helicopter the captain had decided that it was safe to go into the fjord, provided the ice flights were repeated every hour to make sure the ice island did not rotate southwards and close off the whole entrance. This was the first time I saw the boat in action as a real ice breaker: breaking ice. Quite an experience I must say! Thick floes of ice were crushed by the ship’s bow and pushed sideward. The landscape around us is breathtaking: steep cliffs on both sides of the fjords, on top of the cliffs theGreenland ice sheet, large ice bergs that have calved off from Petermann Glacier in the ocean around us, smaller glaciers flowing into the fjord, and the rest of the ocean around us covered in thick ice floes. The wideness and calmness is amazing. The passengers on the helicopter flights today get a real treat. Apart from the amazing landscape a large group of narwhals (whales with long pointy noses) is spotted. I stay on deck for a long time just to admire in silence.

It takes to halfway the afternoon for the boat to break its way through the ice to the vicinity of the edge of the glacier tongue, where we start a CTD/rosette section across the fjord. I asked Humfrey to add some stations to the schedule, even it would only be the top few hundred meters, to better resolve possible finer structures in the fjord. He agreed and added a ‘shallow’ station in between every planned station, warning us though that the whole operation would then take up to 1 or 2 o’clock in the morning. As I really wanted this data I was willing to stay up that late. Apart from the CTDs and rosettes, which tell us something about the water properties and currents in the fjord, we also want to know what the underwater topography (known as bathymetry) looks like. The only information we have is from previous ships in this area, and that information is extremely limited. We basically don’t know more than that the fjord is at least over 1100m deep and that around the entrance the deep part is separated from Nares Strait by a shallow sill, probably no deeper than 450m deep. Therefore we zigzag from station to station, while recording the depth soundings from the ships. The ship’s echo sounder sends a sound signal out to the bottom and waits till this signal returns. From the time it takes to go to the bottom and back, combined with the speed of sound through the water, the depth of the water under the ship is calculated. So, while covering as much ground as we can, we basically map the bathymetry of Petermann Fjord. Knowledge about the bathymetry is of vital importance to be able to make reliable computer models of the ocean circulation in the fjord.

The zigzagging had one minor disadvantage: it took almost an hour to get from one station to the next. Most of the science team had gone off to bed or for a drink at the bar around 10 o’clock in the evening, while Andreas handled the winch and I monitored the CTD-recordings on the computer screen. Humfrey was also still dedicated to the science being done, but after being satisfied that the depth recordings of the bridge went well around 3 am, he went to bed as well. Although the deep stations were a bit boring to perform (looking at a wire unrolling for 20 min, and then rolling up for 20 min), the data was very exciting and we spent the time in between stations plotting the data, discussing, and going back and forth between the processed data and the rough profiles to see what features were real and which ones may be an artificial side effect of the plotting procedure used. When the last station was finally completed and we finished moving equipment into the container, it was 5 o’clock in the morning (slightly later than the scheduled end time). I decided skipping breakfast in the morning would be an excellent idea and went to bed for a good morning of sleep.

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Posted in Ice Island, Nares Strait 2012, Oceanography, Petermann Glacier, Polar Exploration

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