Tag Archives: glaciers

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

Posted on May 17, 2013 by | 6 Comments

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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Cockpit’s View of Greenland’s Glaciers, Ice-Sheets, and Sea-Ice

Posted on April 10, 2013 by | 4 Comments

The glaciers and ice-sheets of Greenland retreat and melt in a warming world. Towering almost 3000 meters above sea level the ice-sheet is so thick and heavy that it depresses the bedrock underneath below current sea-level. Monitoring the ice-sheet, outlet glaciers, and sea ice of Greenland, NASA’s Operation IceBridge flies aircraft packed with radars, lasers, and optical sensors each spring and summer all over Greenland. There are exciting blogs written by the scientists aboard as they live and work out of Greenland. And today I discovered that they also provide video feeds as their plane conducts measurements. Here is an example from yesterday:

I am not entirely sure on the exact location off south-east Greenland, perhaps this is the area near Helheim Glacier, e.g.,

Greenland's bed-rock elevation from Bamber et al. (2003) digital elevation model based on remotely sensed surveys of the 1970ies and 1990ies gridded at 5 km resolution.

Greenland’s bed-rock elevation from Bamber et al. (2003) digital elevation model based on remotely sensed surveys of the 1970ies and 1990ies gridded at 5 km resolution.

but this will become clear as soon as the data are released to the public. This usually happens within a few months. The wide and open data distribution and access is one of the greatest things about this mission. If you want to see where the plane is now, this is the screenshot I took just now (site)

Locations of NASA's P3 air plane near Jacobshavn Isbrae on April-10, 2013.

Locations of NASA’s P3 air plane near Jacobshavn Isbrae on April-10, 2013.

The evolution of Jacobshavn Isbrae retreat from 1851 through present. [From NASA's Earth Observatory]

The evolution of Jacobshavn Isbrae retreat from 1851 through present. [From NASA's Earth Observatory]

Jacobshavn lost its buttressing ice-shelf during the last decade and now rapidly discharges ice from the Greenland ice-sheet directly into the ocean at a rapid rate. Most likely, the ice-shelf was melted by the ocean from below (Holland et al., 2008). This type of accelerated discharge raises global sea-level, because ice previously sitting on Greenland’s bedrock moves into the ocean where it eventually will melt. In response to the ice removed, the bed-rock rises as there is less mass above it to hold it down (Khan et al, 2010). All this has actually been measured by satellites (mass-loss) and ground-based GPS (bed-rock response). We live in a dynamic and rapidly changing world where our sensors and software show new patterns of physics that have never been seen before. There is so much more to discover …

Csatho, B., Schenk, T., Van Der Veen, C., & Krabill, W. (2008). Intermittent thinning of Jakobshavn Isbræ, West Greenland, since the Little Ice Age Journal of Glaciology, 54 (184), 131-144 DOI: 10.3189/002214308784409035

Holland, D., Thomas, R., de Young, B., Ribergaard, M., & Lyberth, B. (2008). Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters Nature Geoscience, 1 (10), 659-664 DOI: 10.1038/ngeo316

Khan, S., Wahr, J., Bevis, M., Velicogna, I., & Kendrick, E. (2010). Spread of ice mass loss into northwest Greenland observed by GRACE and GPS Geophysical Research Letters, 37 (6) DOI: 10.1029/2010GL042460

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Greenland, Frederica de Laguna, and Early Convergences

Posted on March 31, 2013 by | 1 Comment

Not sure why, but this 1929 photo of two young scientists working off Greenland has been in my mind for the last 3 days. It shows a 23-year old graduate student of Anthropology from Columbia University, Frederica de Laguna, with one of her mentors, Archaeologist Dr. Therkel Mathiassen from Denmark. They were digging near Upernavik, Greenland for evidence of long-lost people living in north-west Greenland. It changed the life of Frederica de Laguna, the graduate student, as this summer in Greenland revealed the deep passion that she lived for 75 years after this photo was taken: Arctic Anthropology, the study of people, places, cultures. To me the photo shows an exuberant, yet relaxed and deep happiness after tiresome, yet immensely fulfilling work.

Frederica de Laguna with Therkel Mathiassen in 1929 near Upernavik, Greenland. [From Bryn Mawr College's Collections

Frederica de Laguna with Therkel Mathiassen in 1929 near Upernavik, Greenland. [From Bryn Mawr College's Collections]


My strange obsession with Frederica de Laguna relates to convergent story lines that I am still trying to untangle. Her advisor at Columbia was Franz Boas who as a German physicist lived on southern Baffin Island during the First International Polar Year 1883/84 to study “everything” that he saw and experienced around Cumberland Sound which was a northern base for the whaling industry. His description of a massive iceberg is so detailed, that I feel comfortable to conclude, that he describes an ice island from Petermann Glacier about 1600 miles to the north. After his Arctic field work he emigrated to New York to become one of the founders of American Anthropology in the 20th century. Frederica de Laguna was one of his last graduate students, receiving her PhD in 1933 while digging in Alaska.
Inuit women and children visiting the Hans Egede in Greenland in 1930. [From Cambridge University]

Inuit women and children visiting the Hans Egede in Greenland in 1930. [From Cambridge University]


It took Frederica and her companion 18 days to sail from Copenhagen, Denmark to Upernavik, Greenland aboard the Hans Egede. Two of her sailing companions, a Dr. Krueger from Germany and his assistant Age Rose Bjare of Denmark were planing to explore the geology of Ellesmere Island and areas to the west of it in northern Canada and disappeared. In her autobiography she writes succinctly: “I don’t like Dr. Krueger. He thinks too much of himself.” This sentiment is also reflected by the Canadian police officer who described him as a “punk outfit and a badly overloaded sledge.” Her return sail she shared with Dr. Alfred Wegener, a German geophysicist and his group returning from initial explorations of Disko Bay, Greenland testing the first snowmobiles for a larger expedition to take place the following year in 1930. They probably provided one of the first descriptions of Jacobshavn Isbrae, a fast-moving Greenland outlet glacier. In 1929 it still had a substantial ice-shelf that disintegrated the last 15 years and is lost to history.
The evolution of Jacobshavn Isbrae retreat from 1851 through present. [From NASA's Earth Observatory]

The evolution of Jacobshavn Isbrae retreat from 1851 through present. [From NASA's Earth Observatory]


Alfred Wegener lost his life the following year when he tried to rescue companions who maintained a weather station on Greenland’s ice-sheet. His largest scientific contribution was the idea, that continents move, that North-America, Greenland, and Europe once connected, perhaps, and had drifted apart over the millenia. Since he did not have a physical mechanism detailed, it took oceanographers another 50 years to sort that part out, Wegner’s idea of continents adrift was ridiculed by the establishment at the time and eventually forgotten. It took another 30-40 years for it to revolutionize geology as a dynamic discipline. Plate tectonics is the standard now that explains earthquakes, vulcanoes, and much more. It perhaps did not help Dr. Wegner with the geologists like Dr. Krueger, that he was trained in physics, as was Dr. Boas, the advisor of the now renowned Arctic anthropologist Francisca de Laguna of Bryn Mawr College in Pennsylvania.

The observant reader will notice how many Germans are in this set of story lines. Franz Boas was Jewish and thrived,in the Americas, Hans Krueger was a pompous idiot who disappeared, and Alfred Wegener was a tragic hero. All were German scientists, all converged with Frederica de Laguna in 1929 just when she emerged as a powerful mind of her own as a young graduate student in a field dominated by men. When Germany invaded Poland and France 10 years later, Dr. Frederica de Laguna was teaching her passions at Bryn Mawr College outside Philadelphia. When the war came to America, she asked for a leave of absence to serve in Naval Intelligence where she became a Lieutenant Commander. Her superiors at Bryn Mawr considered this a waste of her time, but she disagreed, and so do I. It is the many personal choices we make, both small and large, that form our personal histories, our science, our selves, and the larger history that we all live … [to be continued]

Davis, R. (2006). Frederica de Laguna of Bryn Mawr College Arctic Anthropology, 43 (2), 21-27 DOI: 10.1353/arc.2011.0075

VanStone, J., & de Laguna, F. (1980). Voyage to Greenland: A Personal Initiation into Anthropology Ethnohistory, 27 (2) DOI: 10.2307/481234

Fredericade Laguna in 1993 at age 87; she worked until age 98 [From New York Times, photo by Bill Roth, Anchorage Daily News]

Frederica de Laguna in 1993 at age 87; she worked until age 98. [From New York Times, photo by Bill Roth, Anchorage Daily News]

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Melting Mountain Glaciers: Changing Planet Video

Posted on March 29, 2013 by | Leave a comment

A short video clip explains in stunning clarity how mountain glaciers change. The example is Mount Kilimanjaro in Tanzania, Africa. The video is produced professionally by NBC and NSF and contains actor Gregory Peck, writer Ernest Hemingway, as well glaciologists Lonnie Thompson and Douglas Hardy.

Lonnie Thompson has perhaps traveled the world for ice cores and published its science implications more extensively than anyone else. At a recent meeting in San Francisco I heart him deliver an engaging and fun presentation. His writing is most accessible in terms of clarity and context.

Thompson, L. (2002). Kilimanjaro Ice Core Records: Evidence of Holocene Climate Change in Tropical Africa Science, 298 (5593), 589-593 DOI: 10.1126/science.1073198

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Oceanography and Icebergs in Baffin Bay: LCDR Edward “Iceberg” Smith

Posted on March 27, 2013 by | 2 Comments

In 1928 Edward H. “Iceberg” Smith took the 125 feet long Coast Guard Cutter “Marion” on an 8,100 mile journey from Boston, MA to New York City, NY via Disko Bay, Greenland. Along the way he defined operational Arctic Oceanography to explain and predict iceberg entering the busy sea lanes off North-America. The Titanic was sunk in 1912, the International Ice Patrol was formed in 1914, and LCDR Smith sailed to Greenland in 1928. The data are priceless 85 years later still. I used them to place modern observations from 2003 into a context of climate variations. First, however, let me give credit to one of the pioneers on whose scientific shoulders I stand:

Edward H. "Iceberg" Smith of the US Coast Guard with reversing thermometer.

Edward H. “Iceberg” Smith of the US Coast Guard with reversing thermometer.

“Iceberg” Smith entered the Coast Guard Academy at age 21 in 1910 and served during World War I as a navigator on Atlantic convoy escort duty. After this war his ship was detailed to the International Ice Patrol and he became one of its first scientific observers at age 32 in 1921. As such he was sent for a year to Bergen, Norway in 1925 to learn the latest theories in physical oceanography. Scandinavian explorers like Nansen, Ekman, Sverdrup, Bjerknes, and Helland-Hansen defined physical oceanography at this time by applying physics on a rotating earth to phenomena that they observed from ships sailing at sea or ships frozen in Arctic ice. Much of this revolutionary work is now elementary oceanography taught in introductory courses, but then, nobody knew much about why ice and ocean move they way they do. It was time to put ideas to a thorough test which is what “Iceberg” Smith did, when he got his ship and orders to explore in 1928.

USCGC Marion built in 1927 [from http://laesser.org/125-wsc/]

USCGC Marion built in 1927. Note the scale indicated by a person standing on the lower deck. [From http://laesser.org/125-wsc]

Armed with new ideas, knowledge, and the tiny USCGC Marion “Iceberg” Smith set to out to map seas between Labrador, Baffin Island, and Greenland to explain and predict the number of icebergs to enter the North-Atlantic Ocean. During his 10 weeks at sea he mapped ocean currents from over 2000 discrete measurements of temperature and salinity at many depths. This was before computers, GPS, and electronics. In 1928 this was slow to work with cold water collected in bottles with “reversing thermometers” that cut off the mercury to preserve temperatures measured in the ocean at depth to be read later aboard. Salinity was measured at sea by tedious chemical titrations. Imagine doing all of this from a rocking and rolling shallow draft cutter that bounces in icy seas for 10 weeks within fog much of the time. No radar to warn of icebergs either, and you want to study icebergs, so you move exactly where they are or where you think they are coming from. And they though that the Titanic was unsinkable.

Iceberg in the fog off Upernarvik, Greenland in July of 2003. [Photo Credit: Andreas Muenchow]

Iceberg in the fog off Upernavik, Greenland in July of 2003. [Photo Credit: Andreas Muenchow]

USCGC Healy in northern Baffin Bay in July 2003 with iceberg. Ellesmere Island is in the background.

USCGC Healy in northern Baffin Bay in July 2003 with iceberg. Ellesmere Island is in the background.

The 1928 Marion Expedition was the first US Coast Guard survey in Baffin Bay while the last such expedition took place 2003. Unlike “Iceberg” Smith we then had military grade GPS, radar, and sonar systems. These sensor systems allowed me to directly measure ocean currents from the moving ship every minute continuously from the surface to about 600 meters down. Oh, we also took water samples in bottles, but temperature, depth, and salinity are all measured electronically about 24 times every second. As a result we can actually test, if the physics that had to be assumed to be true in 1928 actually are true. As it turns out, the old theory to estimate currents from temperature and salinity sections works well off Canada, but not so well off Greenland. Furthermore, we found several eddies or vortices in the ocean from the current profiling sonars.

And finally, it took Edward H. “Iceberg” Smith only 3 years to publish most of his data and insightful interpretations while I am still working on both his and my own data 85 years and 10 years later, respectively. Sure, I got more data from a wider range of moored, ship-borne, and air-borne sensors, but I do wonder, if I really consider my data and interpretations as careful and think as thorough as LCDR Smith did. Furthermore, he had no computers and performed all calculations, crafted all graphs, and typed all reports tediously by hand. I would not want to trade, but all this makes me admire his skills, dedication, and accomplishments even more.

Dr Helen Johnson on acoustic Doppler current profiler (sonar to measure ocean velocity) watch aboard the USCGC Healy in Baffin Bay in 2003. [Photo credit: Andreas Muenchow]

Dr Helen Johnson on acoustic Doppler current profiler (sonar to measure ocean velocity) watch aboard the USCGC Healy in Baffin Bay in 2003. [Photo credit: Andreas Muenchow]

P.S.: The New Yorker has three stories on the subject published in 1938, 1949, and 1959. I eagerly await to read those.

ResearchBlogging.orgSmith, E. (1928). EXPEDITION OF U. S. COAST GUARD CUTTER MARION TO THE REGION OF DAVIS STRAIT IN 1928 Science, 68 (1768), 469-470 DOI: 10.1126/science.68.1768.469

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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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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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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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