Tag Archives: Petermann

Land-Fast Ice Cover off North Greenland: Will NASA bite?

Posted on May 17, 2013 by | Leave a comment

When a large outlet glacier of North Greenland (Petermann Gletscher) discharged an ice island four times the size of Manhattan in August of 2010, the United States’ Congress held formal inquiries on its cause within days of the event. Congressmen, scientists, and the global media speculated that this event and concurrent severe droughts in Russia and floods in Asia were tied to record-breaking air temperatures and global warming. Reviewing available data, Johnson et al. (2011) cautioned that most melting of floating ice shelves such as Petermann Gletscher is dominated by physical ocean processes below, not above the ice (Reeh, 2001, Rignot and Steffen, 2008). The National Journal asked me to write an essay to answer the question: “Is Climate Change Causing Wild Weather?” which I answered with a nerdy No, but …. Motivated by questions asked during the congressional hearing, I showed that waters in Petermann Fjord (a) originate from the Arctic Ocean to the north, (b) contain heat of Atlantic origin, and (c) have warmed significantly since 2003 (Muenchow et al., 2011).

Petermann Gletscher from MODIS Terra. Repeat NASA along-glacier flight tracks are shown in the left and middle panels. White line across the glacier are ICESat tracks. Thick black line across the glacier near y = 0 km is the grounding line location from Rignot and Steffen (2008). Dark areas within 2 km off the western wall are mountain shadows.

Petermann Gletscher from MODIS Terra. Repeat NASA along-glacier flight tracks are shown in the left and middle panels. White line across the glacier are ICESat tracks. Thick black line across the glacier near y = 0 km is the grounding line location from Rignot and Steffen (2008). Dark areas within 2 km off the western wall are mountain shadows.

When I reported here that the same glacier discharged yet another ice island in July 2012, this one “only” twice the size of Manhattan, I was not so sure anymore, that this was merely another extreme event caused by natural processes. Furthermore, only 4 weeks later I was aboard the CCGS Henry Larsen working in Petermann Fjord and Nares Strait to recover instruments that we had deployed in 2009. Witnessing dramatic change off North Greenland from my first visit in 2003 to my last in 2012, I will send NASA a proposal on monday. If suported, it would enable me to test the idea, that a changing sea ice cover off North Greenland over the last 30 years or so relates to the retreat and decay of glaciers north of 76 N latitude. Most of these glaciers connect the Greenland Ice Sheet to the ocean via floating ice shelves as does Petermann.

This is an image that shows land-fast ice in Nares Strait next to Petermann with the large ice-arch blocking all flow of ice to the south where we see open water or thin ice:

June-10, 2012 MODIS-Terra image showing location of moored array that was deployed in Aug. 2009 to be recovered in Aug. 2012.

June-10, 2012 MODIS-Terra image showing location of moored array that was deployed in Aug. 2009 and that we recovered in Aug. 2012.

Contrast the conditions in June 2012 above with in April of 2009 below. The southern ice-arch failed to form in 2009, there is much open water and loose, thin ice next to Petermann Fjord, but a northern ice-arch formed and prevented all flow of thick ice from the Arctic Ocean into Nares Strait or Petermann to glue it all together as it did in 2012 (or right now for that matter):

Largely ice-free Nares Strait on April 2009 with concurrent ocean velocity.

Largely ice-free Nares Strait on April 2009 with concurrent ocean velocity.

My main question is this: Has the changing sea ice cover next to glaciers anything to do with the break-up of many large glaciers all around North Greenland that we have observed the last few years? Is the removal of the summer sea ice from the many fjords of North Greenland a normal occurrence or is this a new regime that flushes many fjords free of ice in summer? Does the available record of air and ocean observations allow us to explain observed change? I believe that the public has all the data (MODIS, SSM/I, ICESat, etc) to answer these questions, but it will need a little work to actually provide quantifiable answers with error bars to pass academic peer review. Anyone is more than welcome to help and maybe even learn or apply skills for a graduate degree and well-paying jobs in physics or engineering.

ADDENDUM (16:33 EDT): As a result of Greenland losing so much mass and ice, the geographic North Pole started in 2005 to move abruptly towards Greenland. This was reported earlier this week by Nature after the research was accepted for publication at Geophys. Res. Let.

Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519

Münchow, A., Falkner, K., Melling, H., Rabe, B., & Johnson, H. (2011). Ocean Warming of Nares Strait Bottom Waters off Northwest Greenland, 2003–2009 Oceanography, 24 (3), 114-123 DOI: 10.5670/oceanog.2011.62

Reeh, N., H. H. Thomsen, A. K. Higgins, and A. Weidick (2001). Sea ice and the stability of north and northeast Greenland floating glaciers Annals of Glaciology, 33, 474-480

Rignot, E., & Steffen, K. (2008). Channelized bottom melting and stability of floating ice shelves Geophysical Research Letters, 35 (2) DOI: 10.1029/2007GL031765

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Posted in Global Warming, Greenland, Ice Cover, Ice Island, Petermann Glacier

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Petermann Photos, Places, and People

Posted on May 2, 2013 by | 5 Comments

Petermann Gletscher sent off Manhattan-sized islands of ice in 2010 and 2012 that now litter the eastern seaboard of Canada from its farthest northern Ellesmere Island to its farthest eastern Newfoundland. The ice is streaming south along thousands of miles within icy Arctic waters. Petermann Gletscher itself is flat, hard to grasp by the naked eye, its endless expanse of white vanishes into the horizon when we look towards the Greenland Ice Sheet ALONG the glacier:

North-eastern section 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.]

North-eastern portion of Petermann Glacier on Aug.-11, 2012, the meandering river is the centerline, view is almost due east with Kap Fulford and Kap Agnes on the left center and Daugaard Jensen Land in the background on the right. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

Next, lets look ACROSS Petermann from roughly the same latitude. This perspective is more dramatic as vertical cliffs give shape, cliffs are cut by smaller side-glaciers. More specifically, we see the CCGS Henry Larsen helicopter flying down Belgrave Glacier as we look across Petermann which flows from the Greenland Ice Sheet on the left out to sea on the right. On the other (south-western) side we see Faith Glacier in the background about 10 miles away.

Seaward front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier towards the south-east across Petermann Fjord with Petermann Gletscher to the left (east). [Photo Credit: Erin Clarke, Canadian Coast Guard Ship Henry Larsen]

Seaward front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier (Belgrave Gl.) towards a similar glacier (Faith Gl.) across Petermann Fjord with Petermann Gletscher flowing from the left out to sea on the right. [Photo Credit: Erin Clarke, Canadian Coast Guard Ship Henry Larsen]

Contrasting large Petermann Gletscher, the many smaller glaciers on both its sides evoke drama as ice plunges down from 3000 feet above in a rage of forms, colors, and shapes. These side glaciers have their own side glaciers that sometimes rival the Alpine glaciers in Europe, Asia, and the Americas that most of us are more familiar with.

Some side glaciers have names, but they are rarely seen on maps and charts. The side glaciers are mapped, but photos are hard to find. Flying over them last year, I was utterly lost. Reviewing photos now, I remember people, smells, computer troubles, and exciting ocean discoveries. Nevertheless, I am hard pressed to place the places we saw on a map or name them. Distances are deceiving, the air is clean and 50-80 miles of visibility are common. A moment later, I cannot see the other side of the ship as we are suddenly in clouds and fog. Everything is always in motion, the ice, the water, the ship, the clouds, all of this without strong reference points like the exit or distance signs on a Turnpike, Interstate, or Autobahn.

Northern Kennedy Channel near the entrance to Petermann Fjord with Kap Morton in cloud banks. [Credit: Andreas Muenchow]

Northern Kennedy Channel near the entrance to Petermann Fjord with Kap Morton in cloud banks. [Credit: Andreas Muenchow]

And along comes Espen Olsen, a frequent contributor to Neven’s Arctic Sea Ice blog and forums, and discovers a plethora of names that I can check, google, and use to remember expeditions to Petermann over the last 10 years with many good friends. So with his help and that of other explorers like Lauge Koch, Tony Higgins, and the collected wisdom of the U.S. Defense Mapping Agency, I labeled some prominent glaciers and capes on an Aug,-21, 2012 MODIS-Terra image that I constructed from data that NASA provide to anyone free of charge. I chose this image and time, because the 2012 ice island is already in Nares Strait and thus out of sight:

Names of glaciers, capes, islands in Petermann Region over MODIS of Aug.-21, 2012.

Names of glaciers, capes, islands in Petermann Region over MODIS of Aug.-21, 2012.

Espen tells me that his Danish sources are protected by copyright (I still like to cite them), but the aviation maps of the U.S. military are in the public domain and can be downloaded from the University of Texas in Austin Library, e.g.,

Petermann Gletscher and surroundings extracted from U.S. Defense Mapping Agency Chart ONC A5 (January 1991).

Petermann Gletscher and suroundings extracted from U.S. Defense Mapping Agency Chart ONC A5 (January 1991).

while the modified version of Figure-2 from Dr. Tony Higgins 1990 publication is available at the Alfred Wegener Institute. Nevertheless, it should only be used for non-profit educational purposes or as a reference:

Petermann Gletscher extend and topography from 1953 through 1978 (from Higgins, 1990) with 2012 terminus position drawn in by hand.

Petermann Gletscher extend and topography from 1953 through 1978 (from Higgins, 1990) with 2012 terminus position drawn in by hand.

With all these details out-of-the-way, we can now start placing photos into places and add names to them. Perhaps others like Espen Olsen can write or edit Wiki entries or correct the false latitude and longitudes that populate the many databases that provide such information on the web. Over the next weeks and months I will try to post as many photos of Petermann’s natural beauty along with an evolving MODIS map that names and shows places. Here are just a few teasers without further comment except what’s in the captions.

The merging of Sigurd Berg and Hubert Glaciers which discharge into Petermann Gletscher on its eastern wall. The view is landward towards the north-east as the helicopter flies in from Petermann. [Credit: Barbara O'Connell, Canadian Coast Guard]

The merging of Hubert (left) and Sigurd Berg (right) Glaciers which discharge into Petermann Gletscher on its eastern wall. The view is landward towards the north-east as the helicopter flies in from Petermann. [Credit: Barbara O'Connell, Canadian Coast Guard]

Petermann Gletscher and Fjord in Aug.-2012. View is to the north-west with Faith Glacier (top left) and Kap Lucie Marie (top right) showing the western wall of Petermann. [Photo Credit: CCGS Henry Larsen]

Petermann Gletscher and Fjord in Aug.-2012. View is to the north-west with Faith Glacier (top left) and Kap Lucie Marie (top right) showing the western wall of Petermann. [Photo Credit: CCGS Henry Larsen]

Looking down Belgrave Glacier discharging into Petermann Gletscher at its terminus in Aug. 2012 [Credit: CCGS Henry Larsen]

Looking down Belgrave Glacier discharging into Petermann Gletscher at its terminus in Aug. 2012 [Credit: CCGS Henry Larsen]

Higgins, A.K. (1990). Northern Greenland glacier velocities and calf ice production Polarforschung, 60, 1-23 Other: 0032-2490

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Posted in Greenland, Ice Island, Nares Strait 2012, Petermann Glacier

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Petermann Glacier Ice Islands: Where are they now?

Posted on January 30, 2013 by | 4 Comments

Two large calving events in 2010 and 2012 reduced the floating part of Petermann Gletscher by 44 km (28 miles) in length, 6 Manhattans (380 km^2) in area, and 42 gigatons in mass. But what’s a gigaton? Writing in The Atlantic Magazine, Julio Friedman states that if we put all people living on earth onto a scale, then we will get half a gigaton. So, Petermann’s two ice island weigh more than eighty times as all humanity combined. As a reminder, this is what the break-ups looked like:

Petermann Gletscher in 2003, 2010, and 2012 from MODIS Terra in rotated co-ordinate system with repeat NASA aircraft overflight tracks flown in 2002, 2003, 2007, and 2010. Thick black line across the glacier near y = -20 km is the grounding line location from Rignot and Steffen (2008).

Petermann Gletscher in 2003, 2010, and 2012 from MODIS Terra in rotated co-ordinate system with repeat NASA aircraft overflight tracks flown in 2002, 2003, 2007, and 2010. Thick black line across the glacier near y = -20 km is the grounding line location from Rignot and Steffen (2008).

It turns out that the smaller 2012 ice island is just as heavy as the 2010 island, because it is much thicker, about 200 m, 600 feet, or half the height of the Empire State Building in Manhattan. These thick and thin islands have since left Petermann Fjord and Nares Strait for more southern climes. The thinnest piece reached Newfoundland in the summer of 2011 where it melted away. Most of the thicker, larger, and heavier ice islands from Petermann and Ryder Glaciers now litter almost the entire eastern seaboard of Canada as the two largest pieces have split, broken, and splintered into many smaller pieces. Each of these still represents an exceptionally large and dangereous piece of ice that can wipe any offshore oil platform off its foundation. Luc Desjardins of the Canadian Ice Service now tracks more than 40 segments, some still bigger than Manhattan, some as small as a football field. The distribution along the 1500 km (1000 miles) of coast is staggering:

RadarSat imagery of eastern Baffin Island (bottom, right), western Greenland (top, right), and Nares Strait with Petermann Fjord (top, left) with pieces of Petermann and Ryder Ice Islands identified. [Credit: Luc Lesjardins, Canadian Ice Service]

RadarSat imagery of eastern Baffin Island (bottom, right), western Greenland (top, right), and Nares Strait with Petermann Fjord (top, left) with pieces of Petermann and Ryder Ice Islands identified as green dots. [Credit: Luc Lesjardins, Canadian Ice Service]

What stands out is that most pieces are close to the coast of Canada. This is expected, because often the ocean moves in ways to balance pressure gradient and Coriolis forces as we live on an earth that rotates once every day around its axis. This force balance holds both in the ocean and the atmosphere. We are all familiar with winds around a low-pressure system such as Hurricane Sandy where the winds move air counter-clockwise around the eye (the center of low pressure). This eye of low pressure in our ocean story is permanently near the center of Baffin Bay. Ocean currents then move water counter-clockwise around this eye. This results in a flow to the south off Canada and a flow to the north off Greenland. On a smaller scale this balance holds also, such as Delaware Bay or Petermann Fjord, but I will not bore you with the details of graduate level physics of fluids in motions … as important as they may be.

So, almost all the ice islands we see in the above imagery will make their way further south towards the Grand Banks off Newfoundland. Some are grounded to the bottom of the shallow coastal ocean and may sit in place for a year, or a month, or until the next high tide will lift the ice off the bottom and move it back into deeper water. Some ice islands will keep moving rapidly, some will further break apart, but none will go away anytime soon. If you want to see some of Petermann’s Ice Islands for yourself, take the ferry from North Sidney, Nova Scotia to Port aux Basques, Newfoundland and Labrador and head for the Great Northern Peninsula. That’s what I hope to do one of the next summers.

ResearchBlogging.org
Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519

Münchow, A., & Garvine, R. (1993). Dynamical properties of a buoyancy-driven coastal current Journal of Geophysical Research, 98 (C11) DOI: 10.1029/93JC02112

Rignot, E., & Steffen, K. (2008). Channelized bottom melting and stability of floating ice shelves Geophysical Research Letters, 35 (2) DOI: 10.1029/2007GL031765

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Posted in Ice Island, Petermann Glacier

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Shots of Airborne Lasers at Petermann Gletscher, Greenland

Posted on November 25, 2012 by | Leave a comment

If shots of whiskey make you dizzy, shots of laser stun. NASA stunned me this week, when I discovered that they provide millions such shots of Greenland from which to construct detailed images of the landscape. The shots are free, no age-limit. This is better than the usual remote sensing or photography of “just” brightness. The laser gives us height, and not just the perception of it by shadows and fake angles of illumination, but hard and direct measurements of, well, height above sea level. Have a look at several million such shots of Petermann Gletscher taken in 2010 before the glacier broke to Manhattan-sized pieces:

Petermann Glacier surface elevation from laser shots on Mar.-24, 2010 at the site where the Manhattan-sized ice island formed Aug.-6, 2010. The background shows the same scene at the same time at 250-m resolution from MODIS (see below). Colors along the 350-m wide laser track line show height above sea level in meters.

Petermann Glacier on March 24, 2010 as seen from MODIS satellite at 250-m resolution with two flight tracks along which laser data are collected. The black box shows the site of the figure above. The color figure on the right shows the slope or gradients of the data shown on left. It emphasizes regions where brightness changes fast. Multivariate calculus is useful!

We see two tracks: the one on right (east) has the ice stick more than 20-m above sea level (yellow colors) while about a mile to left (west) the ice’s surface elevation is only 10-m above sea level (light blue). Since the ice is floating and densities of ice and water are known, we can invert this height into an ice thickness. Independent radar measurements from the same track prove that this “hydrostatic” force balance holds, the glacier is indeed floating, so, multiply surface elevation by 10 and you got a good estimate of ice thickness. The dark blue colors of thin ice show meandering rivers and streams, ponds and undulations, as well as a rift or hairline fracture from east to west. This rift is visible both in the right and left track, it is the line along which the glacier will break to form the 2010 ice island. All ice towards the top of this rift has long left the glacier and some of it has hit Newfoundland as seen from the International Space Station by astronaut Ron Garan:

Last remnant of Petermann Ice Island 2010-A as seen from the International Space Station on Aug.-29, 2011 when it was about 3.5 km wide and 3 km long [Photo credit: Ron Garan, NASA]

Both are images of Petermann ice. The photo measures the brightness that hits the lens, but the laser measures both brightness and ice thickness. The laser acts like flash photography: When it is dark, we use a flash to provide the light to make the object “bright.” Now imagine that your camera also measures the time between the flash leaving your camera and brightness from a reflecting object to return it. What you think happens at an instant actually takes time as light travels fast, but not infinitely fast. So you need a very exact clock to measure the distance from your camera to the object. Replace the flash of the camera with a laser, replace the lens of your camera with a light detector and a timer, place the device on a plane, and you got yourself an airborne topographic altimeter. So, what use is there for this besides making pretty and geeky pictures?

The laser documents some of the change in “climate change.” Greenland’s glaciers and ice-sheets are retreating and shrinking. Measuring the surface and bottom of the ice over Greenland with lasers and radars gives ice thickness. The survey lines above were flown in 2002, 2003, 2007, 2010, and 2011. These data are a direct and accurate measure on how much ice is lost or gained at Petermann Gletscher and what is causing it. My bet is on the oceans which in Nares Strait and Petermann Fjord have increased the last 10 years to melt the floating glacier from below.

There is more, but Mia Zapata of the Gits sings hard of “Another Shot of Whiskey.” What a voice …

ResearchBlogging.org

Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519

Krabill, W., Abdalati, W., Frederick, E., Manizade, S., Martin, C., Sonntag, J., Swift, R., Thomas, R., & Yungel, J. (2002). Aircraft laser altimetry measurement of elevation changes of the greenland ice sheet: technique and accuracy assessment Journal of Geodynamics, 34 (3-4), 357-376 DOI: 10.1016/S0264-3707(02)00040-6

Münchow, A., Falkner, K., Melling, H., Rabe, B., & Johnson, H. (2011). Ocean Warming of Nares Strait Bottom Waters off Northwest Greenland, 2003–2009 Oceanography, 24 (3), 114-123 DOI: 10.5670/oceanog.2011.62

Thomas, R., Frederick, E., Krabill, W., Manizade, S., & Martin, C. (2009). Recent changes on Greenland outlet glaciers Journal of Glaciology, 55 (189), 147-162 DOI: 10.3189/002214309788608958

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Posted in Ice Island, Petermann Glacier, Polar Exploration

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Nares Strait Ice Arches and Petermann Ice Island 2012

Posted on November 13, 2012 by | 2 Comments

Arching barriers of ice locked solidly to land are presently closing off Nares Strait for all ice leaving or entering this ocean passage from the Arctic to the North Atlantic Oceans. Gothic cathedrals have flying buttressing to hold them in place while ice arches have buttressing land that keeps them stable. The sea ice becomes land-fast until these ice arches collapse in June or early July. As the ocean under the ice is still moving, generally from north to south, one often finds very thin ice or even open water to the immediate south of these ice arches. Some of these temperature signals let us “see” large ice structures even in the dark of night which in Nares Strait lasts from early October to late March.

Surface temperature in degrees Celsius for Nares Strait on Nov.-10, 2012 from MODIS Terra. Thick ice is blue (cold) while thin ice is red (warm).

Surface temperature at the northern entrances to Nares Strait with the Arctic Ocean to the north.

Surface temperature at the southern entrance of Nares Strait with the North Atlantic Ocean to the south.

Southern entrance of Nares Strait as seen from RADARSAT showing ice arch formation in more spatial detail than MODIS temperatures do. Note the embedded ice island PII-2012 from Petermann Gletscher at the north-eastern edge of the ice arch. [Credit: Luc Desjardins, Canadian Ice Service]

These ice arches usually form in December or January, but this year they form a little earlier than usual. In some years such as 2006/07 or 2009/10 and 2010/11 they did not form at all and thick multi-year ice left the Arctic via a passage that is now closed. This leaves only Fram Strait to the east of Greenland for such export this year.

It appears that the large ice island that broke free from Petermann Gletscher earlier this year provides some stabilizing support to the southern ice arch as it is anchoring its north-eastern corner where it is possibly grounded. The depth of the ice island PII-2012-A1 is about 180 to 200 meters thick. I derived this estimate from both NASA’s Airborne Topographic Mapper (ATM) and the University of Kansas’s Radar Depth Sounder both flown concurrently on a DC-8 plane that surveyed Petermann Gletscher on May-7, 2011 with PII-2012-A1 still attached:

Profile of Petermann Glacier from laser (red) and radar (black) measurements on May-07, 2011. The 2012 break-up is indicated by a spike of the red under-ice topography near km-22. Bottom profiles from laser assume hydrostatic balance of floating ice.

The ATM is a scanning laser that measures the distance from the DC-8 to the surface within 0.2 meters (about 6-7 inches). If I know both the true sea level surface (I do, it’s called the geoid) and if the ice is floating undisturbed, then I can convert the surface elevation into a bottom draft. The red curve outlines the “theoretical” bottom of the glacier. This curve is masked by a thicker black curve that is a radar-derived image of the under-side of the glacier. Nothing theoretical about that one. These radar measurements agree closely with the red curves indicating an almost perfectly balanced floating glacier. This “balance” breaks down at two important points: (1) Near -20 km the glacier bottom is shallower than the red draft curve and it is here that the glacier sits on land as it is not floating. (2) Near +22 km we see a large red spike. This is the location of the 2012 break-up.

So, the 2012 ice-island that is anchoring the ice arch in southern Nares Strait is the piece of the glacier to the right of the red spike and with these data I can now conclude that PII-2012 was 11 km long, 15 km wide, and about 200 m deep. This Manhattan-sized ice-cube weights about 30 gigatons (10^12 kg), but “… that doesn’t mean much — who goes to the store and buys a gigaton of carrots? For a sense of perspective, a gigaton is about twice the mass of all people on earth …” [James Fallows writing for The Atlantic]. Hence this little ice-cube weights 50 times as much as do all people living on earth today. Incidentally, it is also the amount of CO2 that all humanity adds each year to the atmosphere. Coincidence.

Front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier towards the south-east across Petermann Fjord with Petermann Gletscher to the left (east). [Photo Credit: Erin Clark, Canadian Coast Guard Ship Henry Larsen]

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Petermann and Ryder Glacier Ice Island

Posted on October 22, 2012 by | 5 Comments

Ice island from 2010 and 2012 calvings litter Nares Strait and northern Baffin Island, Canada. All these glacier fragments originate from Petermann and Ryder Gletscher in north-west Greenland. The image below is a composite that Luc Desjardins of the Canadian Ice Service compiled from RadarSat imagery. He painstakingly identified 25 segments in these imagery.

Ice Islands and fragments from Petermann and Ryder glacier 2010 and 2012 calvings. [Credit: Luc Desjardings, Canadian Ice Service]

The largest piece is PII-2012-A1 and it covers an area a little less than 2 Manhattans (100 km^2). We see it in Kane Basin for several weeks now as it pivots back and forth with the tides around the point where it is stuck to the bottom of the ocean. The second largest piece is RII-2012 roughly half the size of Manhattan (33 km^2) and it originates from Ryder Gletscher which is to the north by north-east of Petermann Gletscher. Trudy Wohleben identified this piece when it was entered Nares Strait from the north about 4 weeks ago and together we traced it back to Ryder Gletscher where it had lingered for several years. RII-2012 is now moving rapidly south and is about exit Nares Strait to enter Baffin Bay:

Two of these ice island send their position several time each day with the data made available at for PII-2010-B-a (9 km^2) and for PII-2012-A2 (13 km^2). The last piece broke off from Petermann on July 16, 2012 and it entered Nares Strait in August when we passed it during our explorations of Petermann Fjord on Aug. 10/11, 2012 aboard the CCGS Henry Larsen:

Canadian Coast Guard Ship Henry Larsen at the entrance to Petermann Fjord on Aug.-10, 2012. The ice island PII-2012 is in the background with puddles on sea ice in the foreground. Polaris Bay, Greenland is in the far back. [Photo Credit: CCGS Henry Larsen and Jo Poole.]

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Petermann Glacier Shape and Melt Channels

Posted on September 27, 2012 by | 7 Comments

Radars, lasers, and fancy computers all shape the way we see the shape of glaciers. An airplane flies along a line down the glacier with (1) a good GPS. It carries (2) a vertical laser that measures the distance from the plane to the surface below while (3) an ice-penetrating radar measures where the ice meets the ocean. All these data are distributed freely by the University of Kansas’ Center for Remote Sensing of Ice Sheets (CReSIS) that is part of NASA’s Operation IceBridge.

March-24, 2010 view of Petermann Glacier from NASA’s DC-8 aircraft. Photo credit goes to Michael Studinger of NASA’s IceBridge program who also blogged about this flight.

From CReSIS I gathered the data from Petermann Glacier before its break-up in 2010 and 2012. I show two flight tracks on a MODIS map for the same day that NASA’s DC-8 was collecting the shape data. There are two tracks as the airplane flies along the fjord out towards the ocean, turns, and flies back up inland. The seaward (red) track is slightly offset from the landward (black) track.

Petermann Glacier on March 24, 2010 from MODIS. The left panel shows the reflectance while the right panel shows the magnitude of the spatial gradient of this signal. Red and black dots are the flight tracks from which the shape of the glacier was measured by radar flown on a DC-8. The dark black line indicates where the glacier is grounded to bed rock ~500 meters below sea-level. The 3 boxes indicate location where the floating ice shelf terminated before 2010 (top box), after 2010 (middle box), and now (bottom box) due to the 2010 and 2012 ice islands. Top left are clouds, mountain shadows on left also.

The laser gives us the top surface of the ice while the radar gives us the bottom surface. Connect these two and we get ice thickness. Below I show how these ice elevations change along the glacier. The ocean is to the right near 65 km while the grounding line of the glacier is near -20 km, so the part of the glacier that is floating on the ocean was about 80 km in 2010, that’s about 50 miles. Now why is the red shape so different from the black line?

Shape of Petermann Glacier’s floating ice shelf on March 24, 2010 (top panel) and ice thickness (bottom panel). Radar data from University of Kansas, Center for Remote Sensing of Ice Sheets (CReSIS) with EGM2008 geoid corrections applied by me.

Well, the two tracks were NOT the same and these data show that the glacier varies in thickness and shape at small scales. The floating ice-sheet has lots of topography. It has hills, valleys, channels, and troughs. It stuns me to see how long and how steep this one specific channel is: it changes by almost 200 meters in 2 km. That’s huge. We do not fully understand how these channels form, why they are there, if they change over time, or perhaps most importantly, how do they relate to the stability of this or other glaciers. A first theoreticial PhD thesis was recently submitted by Carl Gladish. It is thought-provoking, but it does not settle the issue. We do not even know how many such channels there are, but there are ideas on how to perhaps do this with data both in hand and more to be collected.

Simplifying future analyses, I changed my Petermann MODIS and CReSIS co-ordinate system from latitude and longitude to a distance in kilometers along and across the glacier. The standard MODIS “color” (lets call this f) varies as one walks the glacier in its along-stream (call this x) and across-stream (call this y) directions. The color f is a function of x and y which scientists write as f=f(x,y). Now compare this color f(x,y) with the SPATIAL CHANGE (call this the slopes) of color that I show in the right panel. The MODIS data are the same, but why do they look so different in the two panels?

Well, the slopes draw the eye to smaller scale features in the right panel. This technique sharpens edges, fronts, and small spatial irregularities that our eyes tend to skip over. Our brains are trained to integrate and to condense information looking for the largest patterns first. So, taking the difference between adjacent values to get slopes and shapes, I do exactly the opposite and make sure that small irregularities stand out:

Close-up of March 24, 2010 MODIS image from the grounding line (black line at bottom) to the location of the present seaward front of the glacier (black box at top).

Notice the many stripes along the glacier near the bottom (x=0) right (y=80) near where the red triangle is. I believe these structures relate to sub-surface melt-channels of intense ice-ocean interactions, but belief is not truth and as scientists we must proof our believes and truths in ways that other people can check by repeating the experiments or calculations. There is so much more fun work to do, but, sadly, there are only 24 hours to a day.

Oh, and a (British) submarine is perhaps on the way to dive under this ice-shelf to take a close look and lots of data of under-ice topography, temperature, salinity, and bottom topography, if we can get a ship and experiment to get it there. So much work to do … [to be continued]

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CCGS Henry Larsen: People, Places, Services

Posted on September 10, 2012 by | Leave a comment

The Canadian Coast Guard Ship Henry Larsen sailed this summer on a challenging science mission to Nares Strait, Petermann Glacier, and beyond. It reached its farthest North ever at 82 degrees and 15 minutes North latitude. This week I like to focus on the 39 people who make this ship what it really is: a complex community with all the functionality of a city. Captain Wayne Duffett is in overall command. His job will overwhelm lesser minds as he has to manage an airport, a fire department, a power plant, a sanitation department, a hospital, a restaurant, a hotel, a supermarket, a weather station, a port facility, a civil administration, etc., etc. Oh yeah, The CCGS Henry Larsen is also a ship that he moves through ice in uncharted waters to support 8 scientists from 3 countries. All of this is done with only 22 crew and 17 officers who work around the clock on a variety of schedules.

CCGS Henry Larsen next to the Petermann Ice Island PII-2012 on Aug.-10, 2012. The south-western tip of PII-2012 at the bottom right of the image was used by Captain Wayne Duffett as a reference point for the motion of PII-2012. The exact place of this point was monitored at hourly intervals via helicopter while the ship was operating inside the fjord landward of the ice island. [Photo Credit: Canadian Coast Guard Ship Henry Larsen/Jo Poole]


Canadian Coast Guard Ship Henry Larsen at the entrance to Petermann Fjord on Aug.-10, 2012. The ice island PII-2012 is in the background with puddles on sea ice in the foreground. Polaris Bay, Greenland is in the far back. [Photo Credit: CCGS Henry Larsen and Jo Poole.]

The ship may occupy an area of only 2,000 m^2 (100 meters long and 20 meters wide), but it functions as a self-contained universe at sea. Perhaps the most important and largest department with 13 people is the power plant that produces energy to move the ship and to provide electricity and heat to make all other departments’ work possible. The 13 members are quiet and thoughtful men often working in the background in cramped, hot, and dirty spaces below decks. It is very hard to get good pictures of them, but here are two, one of Chief Engineer William Derraugh and Second Electrical Officer Anatoly Eltsov:

Chief Engineer William Derraugh on the bridge of the CCGS Henry Larsen in Aug.-2012 with Senior Scientist Dr. Humfrey Melling. [Photo Credit: Barb O'Connell, Canadian Coast Guard.]


Electrical Officer Anatoly Eltsov during a thoughtful moment on the bridge of the Canadian Coast Ship Henry Larsen in Nares Strait. [Photo Credit: Kirk McNeil, Canadian Coast Guard]

The second-largest department is the fire department that also run the port facilities, the fishing fleet, and provide general support on deck, on the bridge, on the water, and on land to a range of activities. There are nine men in this department that are led by the boatswain or bosun Don Barnable with Chief Officer Brian Legge in command. The men of this department are perhaps the most vocal and visible on the ship as they work so many jobs wearing many hats, uniforms, and arms. I can and will fill entire picture galleries of their work, here are just three images that barely serve as teasers, perhaps:

Boatswain Don Barnable and Seaman Derick Stone working at the airport aboard the CCGS Henry Larsen as traffic control and fire fighter, respectively. [Photo Credit: Jo Poole, British Columbia]


Zodiac of the CCGS Henry Larsen recovering a mooring in Kennedy Channel on Aug.-6 with Chief Officer Brian Legge at the helm. Ellesmere Island, Canada is in the background. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]


Deck crew of CCGS Henry Larsen led by boatswain Don Barnable (white helmet) recovering a mooring over the side where the zodiac delivered it to the crane. Two scientists in the background waiting for the deck to be secure. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]

I will have to stop here for now, and will report tomorrow and thursday about the logistics, communication, aviation, hospital, and civil administration departments. There is just too much going on aboard a ship that acts like a complex, advanced, and very mobile city. And with mobile I do not just mean a structure of steel, but a structure made of sailors, navigators, scientists, and engineers.

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Petermann Ice Island 2012 Breaking Up

Posted on September 2, 2012 by | 4 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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