Tag Archives: ice

The Turbulence of Van Gogh and the Labrador Shelf Current

Posted on May 8, 2013 by | 2 Comments

Vincent Van Gogh painted his most turbulent images when insane. The Labrador Current resembles Van Gogh’s paintings when it becomes unstable. There is no reason that mental and geophysical instability relate to each other. And yet they do. Russian physicist Andrey Kolmogorov developed theories of turbulence 70 years ago that Mexican physicist applied to some of Van Gogh’s paintings such as “Starry Sky:”

Vincent Van Gogh's "Starry Sky" painted in June 1889.

Vincent Van Gogh’s “Starry Sky” painted in June 1889.

The whirls and curls evoke motion. The colors vibrate and oscillate like waves that come and go. There are rounded curves and borders in the tiny trees, the big mountains, and the blinking stars. Oceanographers call these rounded curves eddies when they close on themselves much as is done by a smooth wave that is breaking when it hits the beach in violent turmoil.

Waves come in many sizes at many periods. The wave on the beach has a period of 5 seconds maybe and measures 50 meters from crest to crest. Tides are waves, too, but their period is half a day with a distance of more than 1000 km from crest to crest. These are scales of time and space. There exist powerful mathematical statements to tell us that we can describe all motions as the sum of many waves at different scales. Our cell phone and computer communications depend on it, as do whales, dolphins, and submarines navigating under water, but I digress.

The Labrador Shelf Current off Canada moves ice, icebergs, and ice islands from the Arctic down the coast into the Atlantic Ocean. To the naked eye the ice is white while the ocean is blue. Our eyes in the sky on NASA satellites sense the amount of light and color that ice and ocean when hit by sun or moon light reflects back to space. An image from last friday gives a sense of the violence and motion when this icy south-eastward flowing current off Labrador is opposed by a short wind-burst in the opposite direction:

Ice in the Labrador Current as seen by MODIS-Terra on May 3, 2013.

Ice in the Labrador Current as seen by MODIS-Terra on May 3, 2013. Blue colors represent open water while white and yellow colors represent ice of varying concentrations.

Flying from London to Chicago on April 6, 2008, Daniel Schwen photographed the icy surface of the Labrador Current a little farther south:

Ice fields seen in Labrador Current April 6, 2008 from a plane. [Photo Credit: Daniel Schwen]

Ice fields seen in Labrador Current April 6, 2008 from a plane. [Photo Credit: Daniel Schwen]

Ice in the Labrador Current as seen by MODIS-Terra on April 6, 2008. Blue colors represent open water while white and yellow colors represent ice of varying concentrations.

Ice in the Labrador Current as seen by MODIS-Terra on April 6, 2008. Blue colors represent open water while white and yellow colors represent ice of varying concentrations.

The swirls and eddies trap small pieces of ice and arrange them into wavy bands, filaments, and trap them. The ice visualizes turbulent motions at the ocean surface. Also notice the wide range in scales as some circular vortices are quiet small and some rather large. If the fluid is turbulent in the mathematical sense, then the color contrast or the intensity of the colors and their change in space varies according to an equation valid for almost all motions at almost all scales. It is this scaling law of turbulent motions that three Mexican physicists tested with regard to Van Gogh’s paintings. They “pretended” that the painting represents the image of a flow that follows the physics of turbulent motions. And their work finds that Van Gogh indeed painted intuitively in ways that mimics nature’s turbulent motions when the physical laws were not yet known.

There are two take-home messages for me: First, fine art and physics often converge in unexpected ways. Second, I now want to know, if nature’s painting of the Labrador Shelf Current follows the same rules. There is a crucial wrinkle in motions impacted by the earth rotations: While the turbulence of Van Gogh or Kolmogorov cascades energy from large to smaller scales, that is, the larger eddies break up into several smaller eddies, for planetary-scale motions influenced by the Coriolis force due to earth’s rotation, the energy moves in the opposite direction, that is, the large eddies get larger as the feed on the smaller eddies. There is always more to discover, alas, but that’s the fun of physics, art, and oceanography.

Aragón, J., Naumis, G., Bai, M., Torres, M., & Maini, P. (2008). Turbulent Luminance in Impassioned van Gogh Paintings Journal of Mathematical Imaging and Vision, 30 (3), 275-283 DOI: 10.1007/s10851-007-0055-0

Ball, P. (2006). Van Gogh painted perfect turbulence news@nature DOI: 10.1038/news060703-17

Wu, Y., Tang, C., & Hannah, C. (2012). The circulation of eastern Canadian seas Progress in Oceanography, 106, 28-48 DOI: 10.1016/j.pocean.2012.06.005

→ 2 Comments

Posted in Oceanography

Tagged , , , , , , , , ,

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

→ 4 Comments

Posted in Greenland

Tagged , , , , ,

CCGS Henry Larsen: More on People, Places, and Services

Posted on September 13, 2012 by | 2 Comments

The Canadian Coast Guard Ship is powered by such a diverse and talented group of women and men from Newfoundland, Labrador, and beyond, that one or even two posts here hardly do justice to describe how well they run their ship and its many facilities that many mid-sized cities do not have. Monday I wrote about the people who run the power plant and electric departments as well as the seamen who fight fires and run fishing fleet and port facilities. Today I want to show the airport and talk a little about the civil administration that oversees and manages all aboard the ship.

Landing deck of the CCGS Henry Larsen with aircraft preparing for take-off to survey the ice conditions ahead. Shown are Chief Officer Brian Legge (far right) who is in command of the airport and is talking to Pilot Don Dobbin (2nd from right), scientist Renske Gelderloos (3rd from right), Ice Services Specialist Erin Clarke (4th from right), and Helicopter Engineer Pierre Autran performs last checks inside the helicopter. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]

The airport consists of hangar, landing pad, helicopter, traffic control, and fire fighting stations. Don Dobbin was our pilot and Pierre Autran his engineer who was pulled out of retirement for this trip. Incidentally, Pierre and I had sailed together on the same ship in 1993 more than 200 miles north of eastern Siberia. Then all flights were prohibited by Russian aviation authorities: Politics were different 20 years ago, one hopes. No such threat of being shot down existed this year between Greenland and Canada, but for severe ice conditions and poor internet connections, the airport was very busy almost every day for both ice surveys ahead and behind the ship. It also supported landing parties to set up and/or service 4 weather stations.

Helicopter pilot Don Dobbin with scientist Dave Riedel on Hans Island servicing a weather station in the center of Nares Strait. Ellesmere Island in the background. [Photo Credit: Allison Einolf, Minnesota]

The air traffic control takes place both on the flight deck where Chief Officer Brian Legge is in charge and from the bridge where the officer-of-the-deck is in overall command as either First Officer Chris Steward or Second Officer Rebecca Acton-Bond place the ship, alert the entire ship, and often oversee other science operations as well. All of these are demanding jobs, all these jobs need precision in the concise communication of orders and permissions granted or denied as well as execution of all operations, because helicopter operations are probably one of the most dangerous and critical operations possible on the ship.

Attention to detail, clear communication, and calm execution lower the risk of death and destruction that helicopters can and often do cause. The National Science Foundation sent me to a 4-day course in helicopter safety and what to do if accidents happen over water or on land. It was a sobering course. For this reason, perhaps, Captain Wayne Duffett is almost always on the deck during flight operations, but as all good chief executives, he lets his officers and navigators run the operations but is available for help on consultation should it be needed.

Second Officer and navigator Rebecca Acton-Bond on a sunday on the bridge of the CCGS Henry Larsen in August of 2012 in Nares Strait. [Photo Credit: Canadian Coast Guard, Kirk McNeil, Labrador]

Leading Seaman and helmsman Melvin Cobb on the bridge. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]

The navigator always works with a helmsman or quartermaster who steers the ship following instructions of the officer of the deck, they are on the look-out for ice and bergs to find the best routes. “Best” here refers to the route that requires the least amount of ice breaking. So, if there is one thing that icebreakers like the Larsen are really good at, it is how to avoid ice, because it is a violent and high-energy activity. Fuel is not cheap and less ice is broken, the faster and more efficient the tasks at hand can be accomplished.

And as all people on the ship, everyone has more than one job and this includes the helmsmen and quartermasters like Melvin Cobb or firefighters like Derick Stone, Carl Rose, Paul Gillingham, and Rueben Hillier. They are often members of the deck crew that help landing parties to get ashore and stay save while ashore. This involves the zodiac as well as guns to protect from polar bears:

Seamen Paul Gillingham and Rueben Hillier in the zodiac steered by Chief Officer Brian Legge in Alexandra Fjord, Ellesmere Island on Aug.-13, 2012. A tide gauge was recovered and re-deployed near this site. [Photo Credit: Canadian Coast Ship Henry Larsen, Barbara O'Connell]

Zodiac launched for a landing part to dismantle a weather station at Cape Baird, Ellesmere Island. Chief Officer Brian Legge at the helm with Melvin Cobb and Derick Stone in the back and center left of the boat filled with scientists Humfrey Melling, David Riedel, Andreas Muenchow, and Renske Geldeloos. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]

Landing party at Cape Baird, Ellesmere Island to dismantle a weather station. Scientists David Riedel (foreground) and Humfrey Melling (background) are protected by Melvin Cobb (with gun) from polar bears. View is towards the north-west across Lady Franklin Bay to the west of Nares Strait. [Photo Credit: Renske Gelderloos, Oxford University]

Taking down a weather station on Cape Baird, Ellesmere Island, view is to the south-west. People from right to left, the author, David Riedel (kneeling), Melvin Cobb, and Humfrey Melling (covered). [Photo Credit: Renske Gelderloos, Oxford University]

Polar bear on an ice floe in Kennedy Channel as seen from the bridge as the ship was approaching a station a day’s polar bear walk from Cape Baird. [Photo Credit: Canadian Coast Guard Ship Henry Larsen]

There is still more to describe such as the hospital, the restaurant and bar, as well as the superior fishing of sailors and fishermen from Newfoundland to find and hook valuable items such as sensors and computers that some scientists left unattended for 3 or 5 or 9 years at the bottom of the unspoiled seas that border Arctic Greenland and Canada. There will be more … as there are more great people who make great science possible.

→ 2 Comments

Posted in Nares Strait 2012, Polar Exploration

Tagged , , , ,

Ice Thickness in Nares Strait 2008 and 2009

Posted on August 28, 2012 by | 1 Comment

[Editor's Note: Undergraduate Julie Jones of the University of Delaware summarizes her work that was supervised by Helga Huntley as part of an NSF-funded summer internship.]

Three years ago in 2009 Andreas Muenchow left from Delaware for Greenland with students Pat Ryan and Berit Rabe to recover instruments that recorded salinity, temperature, current velocities, and ice thickness in Nares Strait since 2007.  This summer, I used those observations to estimate ice thickness for April through June in 2008 and compare them to estimates for the same spring period in 2009.  An ice bridge had formed in 2008 but not in 2009.  Working as a group, we wanted to investigate the effect of ice arches on the ice thickness.  Allison Einolf, another summer intern who focused on ocean currents during the same time periods and Andreas produced these maps that introduce the study area, spatial ice cover, and mean ocean currents:

Image

Nares Strait MODIS satellite imagery of the study area and ice arch April 21, 2008. Red dots are instrument locations. Arrows show current velocities.

Image

Nares Strait MODIS satellite imagery of the study area and ice arch April 22, 2009. Red dots are instrument locations. Arrows show current velocities. Note the lack of the southern ice arch, but the presence of one north of the study area.

I used Matlab for most of the data processing, more specifically the Ice Profiling Sonar (IPS) Processing Toolbox for Matlab provided by the manufacturer of the instrument that collected the data: ASL Environmental Sciences, Inc. First I transformed the data from the IPS instrument into a range time series.  I then manually “despiked” the data, taking out any data points that were likely due to bubbles or fish within the acoustic path from the sensor system to the ice above and back.  In a second step I wrote a function using sound speed data from Andreas, atmospheric pressure from Dr. Samelson at Oregon State University, and pressure (depth) data from the IPS instrument to get a time series of the thickness of the ice.  In a third step I applied a Lanczos raised cosine filter that was taught as part of a 2012 Summer Intern Page Workshop. Hence I finally had some nicely filtered data for the periods of the April-June of 2008 and 2009.

Now the results:  Just as we expected, there was much thicker ice in the 2008 spring with a southern ice arch present than there was in the spring of 2009 when no such ice arch was present:

Histogram for April – June 2008 ice. There is a peak at 3 meters, with almost 25% of the ice that thick.

Histogram for April – June 2009 ice. The ice does not get thicker then 2 meters with most of the ice thinner than one meter.

The histograms show thicker ice in 2008, about 2-6 meters on average and with some ice even reaching 10 meters.  In 2009, the ice doesn’t get thicker than 2 meters with most of the ice being thinner than 1 meter.  More specifically, the mean ice thickness for April – June 2008 (2009) is 3.8 (0.58) meters with a standard deviation of 1.8 (0.29) meters.  This further shows that there was thicker ice in 2008 than there was in 2009.  I attributed the cause for the thin 2009 ice to ice flowing freely through Nares Strait all winter and spring as no ice arch in the south blocked such flow.  The ice, thus, did not spend enough time in the high Arctic to thicken.

I noticed something else in my histograms when the 2008 ice bridge collapsed.

April 2008 ice thickness

May 2008 ice thickness

June 2008 Ice Thickness

The monthly histograms show that the ice in April and May is thicker than the ice in June.  We know that the 2008 ice bridge collapsed near June 6th, so it is interesting and it makes a lot of sense that the ice in June would be thinner than the ice two months earlier.

The mean ice thickness for April 2008 was 4.6 meters with a standard deviation of 2.40 meters.  In May 2008 the mean ice thickness was 3.5 meters with a standard deviation of 1.40 meters.  Lastly, in June the mean ice thickness was 3.5 meters with a standard deviation of 1.30 meters.  The ice thickness decreased after April and the variability decreases in June, which helps detect the bridge collapse in the data.

Lastly here are the filtered time series of April – June of 2008 and 2009.

Filtered time series for April – June 2008

Filtered time Series for April – June 2009 with the same scale as 2008 (above figure)

Filtered time series for April – June 2009 with a different scale to see the variability over time more clearly.

Hopefully we can see more interesting and exciting results from the instruments that the Nares Strait team picked up this summer even though they were hit hard by the 2010 Petermann Ice Island!

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

→ 1 Comment

Posted in Ice Arch, Ice Cover, Oceanography

Tagged , , , , , ,

Nares Strait 2012 Ice Arch Collapsing (Updated 6/30)

Posted on June 28, 2012 by | 9 Comments

UPDATE-2 6/30:

June-30, 2012 MODIS-Terra view of the collapsing Nares Strait ice arch. The separation occured at the location where the hairline fracture developed 3 days ago. The collapse is propagating upstream to the north as the buttressing support on the western anchor point near Bache Peninsula and Pim Island was removed.

UPDATE-1 6/29:

June-29, 2012 MODIS-Terra view of the collapsing Nares Strait ice arch. The separation occured at the location where the hairline fracture developed 2 days ago.

The most relevant weather information is from Hans Island near 81 N latitude.

ORIGINAL Post (6/28/2012):
The collapse of the ice-arch in southern Nares Strait began June-27, 2012 with development of a small hairline fracture along the western side of the strait off Ellesmere Island, Canada. The fracture connects an isolated area of open water off Bache Peninsula, Canada at 79 N latitude. The front between land-fast ice in the north and the open water in the south has moved slightly southward. It has also lost a visible larger piece of ice that before anchored the bridge at its western connection to land. This motion will open the hairline fracture more, accelerating the collapse of the ice-arch. The missing support of the ice-arch on its western side will collapse the entire ice-arch and the previously land-fast ice of Nares Strait will stream rapidly to the south, I predict, before this weekend.

Updates (including an animation) will be posted daily at http://muenchow.cms.udel.edu/Nares2012/Kane/.

Ice-bridge at southern Nares Strait June-26, 2012 23:30 UTC from MODIS-Terra. There are no hairline fractures yet along the Ellesmere Island side near 79 N latitude. Greenland is on the right (east), Canada on left (west).

Ice-Bridge at southern Nares Strait on June-27, 2012 17:40 UTC from MODIS-Terra. Notice the crack and hairline fractures in the ice along the Ellesmere Island coast near 79 N latitude and 75 W longitude.

This collapse happens each year in the summer, though the timing varies from April for weak and July for strong arches. The arch in 2012 lasted longer than the one in 2011. No or only weak ice-arches formed at this site in 2007, 2008, and 2009, e.g., http://muenchow.cms.udel.edu/MODIS/.

EDIT-1: Same imagery, same gridding, but more focus and detail

MODIS-Terra June-26, 2012 prior to collapse.

MODIS-Terra June-27, 2012 at the onset of collapse. Note the change near the Canada at 79 N latitude where open waters meets the sea ice.

EDIT-2: The moorings we try to recover this summer are to the north of Kane Basin and to the south where Petermann Fjord enters Nares Strait. This map shows it (also notice how badly the coastline of Greenland is surveyed):

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

→ 9 Comments

Posted in Ice Arch, Ice Cover

Tagged , , ,

Nares Strait Ice Bridge and Arctic Ice Thickness Change

Posted on June 19, 2012 by | 8 Comments

The ice of the Arctic Ocean is rapidly disappearing. This happens every summer, but for the last 30 years there is a little less ice left at the end of each summer than there was the year before. The areas covered by ice are not only shrinking, the ice is also getting thinner, or so many do believe.

To check out such claims, we placed sound systems on the ocean floor of Nares Strait from which to find out how much the thickness of the ice above has changed. We started this in 2003, were told to stop it in 2009, but privately parked our instruments where they would collect data. We must get to check our sound systems and retrieve the private recordings, because otherwise Poseidon will claim our possessions for parking violations. The Canadian Coast Guard Ship Henry Larsen, we hope, will help us to negotiate water and ice to get us deep into Nares Strait as she and her crew did so well in 2006, 2007, and last in 2009.

CCGS Henry Larsen in thick and multi-year ice of Nares Strait in August 2009. View is to the south with Greenland in the background. [Photo Credit: Dr. Helen Johnson]

The ice profiling sonar sounds system before its first deployment in Nares Strait in August 2003 from aboard the USCGC Healy. It measure ice thickness many times each seconds for up to 3 years. View is to the north-west with Ellesmere Island, Canada in the background. Listening in are Jay Simpkins (left), Helen Johnson, and Peter Gamble.

Nares Strait to the west of northern Greenland is one of two major gates for the thickest, the hardest, and the oldest ice to leave the Arctic for the Atlantic Ocean [Fram Strait to the east of Greenland is the other.] This gate is closed at the moment by an arching ice bridge that locks all ice in place. No ice can leave the Arctic via Nares Strait as long as these arches hold. The ice arch acts as a dam that holds back the flood of ice that will come streaming south hard once the dam breaks. And break it will, usually between the end of June and July.

Ice arch in southern Nares Strait as seen by MODIS Terra on June-18, 2012. Greenland is on the right, Canada on the left. The dark blue colors in the bottom-left are open water, yellow are the ice caps of Greenland and Ellesmere Island and lighter shades of blue are warm ice or land. Humboldt Glacier is the on the right-center where Nares Strait is at its widest with Kane Basin at about 80 N latitude.

Nares Strait Jun.-10, 2012 image showing land-fast ice between northern Greenland and Canada as well as the ice arch in the south (bottom left) separating sea ice from open water (North Water). The coastline is indicated as the black line.

The sooner it breaks, the more old ice the Arctic will lose and the better it is for us to get an icebreaker to where must be to recover our instruments and data. The data will tell us if the ice has changed the last 9 years.

I processed and archived maps of Nares Strait satellite images to guide 2003-2012 analyses of how air, water, and ice change from day to day. Ice arches formed as expected during the 2003/04, 2004/05, and 2005/06 winters lasting for about 180-230 days each year. In 2006/07 no ice arch formed, ice streamed freely southward all year, and this certainly contributed to the 2007 record low ice cover. In 2007/08 the arch was in place for only 65 days. In 2009/10, 2010/11, and now 2011/12 ice cover appear normal as the arches formed in December and lasted until July.

We live in exciting times of dramatic change, some to the better and some to the worse. Some of the change is caused by global warming while most is probably not. We do not know for sure, but most of the evidence points towards us people as a major driver of the change we observe in the Arctic and elsewhere. Nevertheless, climate and its change is one grand puzzle that no single scientist, no single discipline, no single country, and no single continent can solve. There are many pieces that all contribute to how and why the Arctic ice changes the way it does. And this includes the ice arches of Nares Strait. There are many mysteries and unresolved physics in what makes these ice arches tick and what makes them blow to bits, but blow they will … watch it, it’s fun, and perfectly natural.

EDIT: This movie shows just how stable the ice arch is at the moment.

→ 8 Comments

Posted in Ice Arch, Ice Cover

Tagged , , , , ,

Heat Sensing Eyes “See” Arctic Ice Thickness

Posted on January 26, 2012 by | Leave a comment

The Arctic sea ice is disappearing before our eyes as we extended them into space in the form of satellites. Every summer for the last few years the area covered by ice is shrinking during the summer when 24 hours of sunlight give us plenty of crisp images. But what about winter? What about now? And does a picture from space tell us how thick the ice is?

Nares Strait between northern Greenland and Canada on Aug.-13, 2005 with Petermann and Humboldt Glaciers at top and center right from MODIS imagery using red, blue, and green channels.

It is dark in the winter near the north pole as the sun is below the horizon 24 hours each day, but there are many ways to “see” in the dark as flying bats aptly show. They send out sound that bounce off objects from which bats reconstruct objects around them. We use radar from space to do to the same with radio waves to “see” different types of ice at night from satellites. We can also use tiny amounts of heat stored in water, ice, snow, and land to “see” at night. Someone breathing down your neck at a cold dark corner will make our heart beat faster as we “see” the heat not with our eyes, but with our skin. I digress, as I really want to talk about icy Arctic seas and how we can perhaps “see” how thick it is with our eyes in the sky.

The most accurate and pain-staking way to measure ice thickness is drill holes through it. This is back-breaking, manual labor away from the comforts of a ship or a camp. One person watches with a shot-gun for polar bear searching for food, not our food, we are the food. The scientist who does this sweaty, dangerous work on our Nares Strait expeditions is Dr. Michelle Johnston of Canada’s National Research Council. She is a petite, attractive, and smart woman who is calm, competent, and comfortable when she leads men like her bear-like helper Richard Lanthier into the drilling battles with the ice. She gets dirty, cold, and wet when on her hands and knees setting up, drilling, cutting, measuring:

Dr. Michelle Johnston assembling ice drilling gear in Nares Strait with Greenland on the horizon. The Canadian Coast Guard Ship Henry Larsen in the background with its helicopter hovering.

She measures temperatures within the ice and tries to crush it to find out how strong it is. All of this information guides ship operators on what dangers they face operating in icy seas. Drilling over 250 such holes across a small floe on the other (eastern) side of Greenland, Dr. Hajo Eicken showed how one large ice floe changes from less 1 meter to more than 5 meters in thickness. He also discovered that the percentage of thick and thin ice of his single 1 mile wide ice chunk is similar to the percentages measured by a submarine along a track longer than 1000 miles.

This was a surprising result in 1989 and we use it to estimate ice thickness more leisurely sipping coffee in our office. From the same satellite that gives us crisp true color images in summer as shown above, we get false color images of temperature as shown below.

Map of Nares Strait, north-west Greenland on March-25, 2009 showing heat emitted during the polar night from the ocean through the ice, and sensed by MODIS satellite.

A graduate student of mine, Claire Macdonald, is trying to convert these temperature readings into ice thickness for Nares Strait. She showed me the first promising results today. The plot below shows the distribution of “thermal” ice thickness for a small square in Nares Strait Dec.-1, 2008 through Mar.-1, 2009 when no clouds were in the area. Note the two distinct and separate clusters with thicknesses below 1 meter and above 2 meters. They represent thin ice formed in 2009 after an upstream ice arch blocked all flow of thicker ice from the Arctic Ocean to Nares Strait. The thicker ice passed the study area at times when the thick, hard multi-year Arctic ice entered Nares Strait freely from the Arctic Ocean.

Distribution of "thermal" ice thickness from satellite for Nares Strait Dec.-1, 2008 through Mar.-1, 2009. (Credit: Claire Macdonald, Jan.-26, 2012)

Much work remains to be done: Claire is comparing the “thermal” ice thickness with “acoustic” ice thickness measured by sonars moored in the water below the ice. It then will be exciting to explore “thermal” thicknesses for all of Nares Strait. Winds and ocean currents will pile ice up in some areas making it thicker while they spread ice out making it thinner. Claire and I have worked with such wind and ocean data. Science is never finished as each question answered raises a host of new ones.

→ Leave a comment

Posted in Ice Cover, Oceanography

Tagged , , , , , , , ,

Pine Island Glacier on the Move

Posted on January 12, 2012 by | 1 Comment

Pine Island Glacier, Antarctica, is the focus of a large observational effort to better understand how glaciers and floating ice shelves interact with the ocean.

Pine Island Glacier (view is to the north, ocean in the top left) with crevasses and large crack extending from the east (right) to the west (left) as seen from aboard NASA's DC-8 research aircraft in October 2011. Credit: Michael Studinger/NASA

Scientists, pilots, technicians, and students working with NASA’s IceBridge and NSF’s Antarctic programmes tried hard for several years now to reach this glacier, set up a base, and drill through the 400-600 m thick ice shelf to reach the ocean. The data from these gargantuan efforts will reveal physics of ice-ocean interactions. This process is poorly represented in the climate models that are used to project past and present climates into the future. Harsh and hostile conditions cut these efforts short today, again, as reported by OurAmazingPlanet.

The expedition leader, NASA’s Dr. Bindschadler wrote today, that

A decision had been made by NSF the day we left McMurdo that if the helos were not able to be flown to PIG by Saturday, January 7, this year’s field work would be cancelled … We worked through our cargo—some had not been seen for two years when we tested our equipment at Windless Bight—preparing for either helos or the Twin Otter to start moving us onto the ice shelf. Neither came. Weather worsened.

Despite this dramatic turn of events, skies were clear over Pine Island Glacier today as they on New Year Jan.1, 2012. Two MODIS images show detailed features at 250-m resolution. I here show the near infra-”red” signals that the satellite receives (865 nm). The dark ocean reflects little of red (low reflectance) as it is all absorbed while the bright snow and ice reflects lots of red (high reflectance). Recall that the color “white” looks white, because it reflects all colors into our eyes including red, while “black” absorbs all colors, so none are left to reach our eyes.

Pine Island Glacier and Bay, Antarctica on Jan.-1, 2012 as seen by MODIS Terra, notice the whitish crack near the center of the image.

I show lots of the near infra-”red” as, well, red, and I color little red as blue. I chose the colors of the “crayons” to do the coloring. The technical term for this is contouring. Formally, I am depicting a function f=f(x,y) where f is the amount of red and x and y are locations east and north, respectively.

Pine Island Glacier and Bay, Antarctica on Jan.-12, 2012 as seen by MODIS Terra, notice the whitish crack near the center of the image.

They almost look the same, don’t they? If they were identical, then the difference would get zero. Except, glaciers move, especially this one. It is also about to spawn a large ice island. A crack was first reported in Oct.-2011 by scientists aboard a DC-8 of a NASA Icebridge flight. This crack is also widening as, I speculate, the front moves faster seaward of the crack than it does landward. My question is if I can see movements in these easily accessible public MODIS images. And my first answer, to be refined later, is 80 meters per day plus or minus 50%:

Difference of reflectance by subtracting Jan.-1 reflectances from those on Jan.-12, 2012. Very dark red colors show large positive numbers, meaning that the ice occupies a place on Jan.-12 that was water on Jan.1.

I am neither a glaciologist nor a remote sensing person, so I may be running a few red lights differencing two images and assign meaning to it. For example, I estimate the speed at which the front of the glacier moves by dividing the width of the very dark thick red line (about 1 km wide) by 12 days to get 80 meters per day or 3.5 meters per hour. The error here is at least 2 pixels (500-m), about half the estimated speed. My assumption here is that the high reflectance on Jan.-12 at a location with a low reflectance on Jan.1 means that the “bright” glacier has moved to a place that was “dark” ocean before. There is more to this, but I have to start somewhere.

Incidentally, Dr. Bindschadler, the leader of the current Pine Island field project who had to leave the base camp near Pine Island Glacier today, is the very person who wrote a wonderful peer-reviewed paper in 2010 with the title “Ice Sheet Change Detection by Satellite Image Differencing.” I will need to study it more closely … along with the vagarities of field work in polar regions.

It is difficult to get data from the field as opposed to data from remote sensing or modeling. This is especially true for remote and hostile locations the ice and the oceans interact. It is frustrating to be sent home early because of inclement weather and the very narrow window of opportunity when the few available helicopters and planes can fly or the ships can sail near Antarctica and Greenland.

EDIT Jan.-13: The National Snow and Ice Center estimated speeds of Pine Island Glacier as determined from two LandSat images from 1986 and 1988:

Contours of glacier speeds in meter per year of Pine Island Glacier from 1986 and 1988 LandSat Imagery, National Snow and Ice Center

These speeds are very different, 2-3 km per year versus 1 km in 12 days. The former estimate is made from 2 carefully geolocated images 2 years apart without a crack across the floating glacier, while my estimate yesterday is more noisy, but it is for a segment of the glacier that is barely connected to it. Perhaps we should consider the segment seaward fo the crack a separate ice island that is moving with the ocean rather than the glacier?

→ 1 Comment

Posted in Ice Island

Tagged , , , , ,

Ice Drift from Nares Strait to Newfoundland: The 1871 Polaris Expedition and Petermann Ice Islands

Posted on January 10, 2012 by | Leave a comment

“Nineteen ship-wrecked members of the Polaris expedition of 1871-72
drifted on ice floes a distance of over 2500 km from Nares Strait near
79°N latitude to Newfoundland. Surviving this six months long ordeal,
they inadvertently mapped for the first time a drift of icy waters
from the Arctic to the North Atlantic Ocean. That they survived to
tell the tale is tribute to two Inuit, Joe Ebierbing and Hans Hendrik,
whose hunting skills and diligence provided food for the entire party
(Hendrik, 1878). Almost a century later, 1962-64, ice island WH-5 was
carefully tracked via ships and aircraft from north of Ellesmere
Island (83°N) to the Atlantic via Nares Strait (Nutt, 1966). The
movements of ice and water so revealed are one link in the global
hydrological cycle whose significance to global climate has yet to be
understood …” [from Muenchow et al. (2007)]

'Captain Hall's Arctic Expedition -- The "Polaris"'', a wood engraving published in ''Harper's Weekly'', May 1873.

The BBC contacted me this morning asking great questions related to the Petermann Ice Islands and icebergs. These reminded me of the opening paragraph quoted from a paper on the oceanography of Nares Strait. I published it in 2007 with two friends and fellow sailors of icy waters, Kelly Falkner and Humfrey Melling. In 2003 we sailed together on the US Coast Guard icebreaker Healy and making detailed measurements on ice, water,and bottom sediments. We reported strong southward currents from the Arctic Ocean into Baffin Bay opposing the local winds. Ocean currents were particular strong about 100 meters below the surface on the Canadian coast of Nares Strait. I am still working on these data as they relate to the flux of fresher Arctic waters into the Atlantic Ocean and their climate impacts.

There is history and drama in these places: Hall Basin is named after the leader of the Polaris Expedition, Charles Francis Hall, an American who was likely poisoned in 1871 with arsenic by his German Chief Scientist Dr. Emil Bessel aboard the Polaris beset in ice in Hall Basin. Bessel has a tiny fjord off Greenland named after him, it is located about 10 miles south of Petermann Fjord, named after August Heinrich Petermann, a German cartographer who traveled little himself but mapped much of what others had traveled. Joe Island, named after the Inuit hunter Joe Ebierbing of the Polaris ice drift, is the island that broke the 2010 Petermann Ice Island at the entrance of Petermann Fjord into PII-A and PII-B. The second Inuit hunter of the infamous 1872 drift, Hans Hendrick has Hans Island named after him which is very much in the center of Nares Strait and is currently claimed by both Canada and Denmark.

The Wikipedia entry on the Polaris Expedition has a well-written introduction while the book by Pierre Berton”The Arctic Grail”provides the story along with many other foolish and professional travails to reach the North Pole during the 19th and early 20th centuries.

→ Leave a comment

Posted in Oceanography, Polar Exploration

Tagged , , , ,

Ice Arch off North-West Greenland Locks Ice Motion in Nares Strait

Posted on December 13, 2011 by | 1 Comment

Winter has come to north-west Greenland as the sea ice of Nares Strait has locked itself to land and stopped movement of all ice from the Arctic Ocean in the north to Baffin Bay and the Atlantic Ocean in the south. While there is no sunlight for several more months now during the polar night, the warm ocean beneath the ice emits heat through the ice which becomes visible to heat-sensing satellites. The light yellow and reddish colors show thin ice while the darker bluish colors show thicker ice today:

Dec.-13, 2011 surface brightness temperature of Nares Strait showing an ice arch in Smith Sound separating thin and moving ice (reddish, yellow) from thick land-fast ice (blue).

The prior 2010/11 winter was the first in several years that these normal conditions have returned. The ice arch in Smith Sound did not form in 2009/10, 2008/09, and 2007/08 winters while a weak arch in 2007/08 fell apart after only a few days. Conditions in 2009 were spectacular, as only a northern ice arch formed. Since the ocean moves from north to south at a fast and steady clip, it kept Nares Strait pretty clear of ice for most of the winter as no Arctic ice could enter these waters and all locally formed new “first-year ice” is promptly swept downstream:

March-25, 2009 map Nares Strait, north-west Greenland showing heat emitted during the polar night from the ocean and sensed by MODIS satellite.

The very thin and mobile ice in Nares Strait of 2009 exposed the ocean to direct atmospheric forcing for the entire year. I reported substantial warming of ocean bottom temperatures here during this period. This new 2011/12 ice arch formed the last few days. If it consolidates during the next weeks, then it is very likely to stay in place until June or July of 2012. It decouples the ocean from the atmosphere and, perhaps more importantly, prevents the Arctic Ocean from losing more of its oldest, thickest, and hardest sea ice. This is very good news for the Arctic which has lost much ice the last few years.

For more daily thermal MODIS imagery take a peek at http://muenchow.cms.udel.edu/Nares2011/Band31/ for 2011. Replace Nares2011 with Nares2003 or any other year, and an annual sequence appears. Furthermore, my PhD student Patricia Ryan just sent me a complete list of files that I need to process until 2017. Fun times.

→ 1 Comment

Posted in Ice Arch, Ice Cover, Oceanography

Tagged , , , , ,