What’s happened at Petermann Gletscher since the Industrial Revolution 150 years ago?

More than 15 years ago I first set sight on the floating Petermann Gletscher when the United States’ Coast Guard Cutter Healy visited north-west Greenland for the first time on 10th August of 2003. We only had to sail 20 km into the fjord to reach a flat expanse of glacier ice that stuck less than 5 m (15 feet) above the sea. In 2012 and 2015 we had to sail another 20 km, because two large calving events had shortened the glacier farther back than it has since first records were kept in 1876. The terminus was also much higher, almost 25 m (75 feet) above the sea:

DSCN4444

Terminus of Petermann Gletscher 5th August 2015 from aboard the Swedish icebreaker Oden. View is to the south-east. [Photo Credit: Andreas Muenchow]

I published more detailed results on observed glacier change and estimated melt rates with Drs. Laurie Padman and Helen Fricker in the Journal of Glaciology from which I take these two figures:

Muenchow2014_01

Petermann Gletscher’s two large calving events in 2010 and 2012 as seen from MODIS satellite. The glacier is floating on the ocean seaward of the grounding line indicated by the thick black line. Black areas are open ocean water, white is ice. Adapted from Muenchow et al., 2014.

Muenchow2014_02

Time series from 1876 to 2014 of the length of Petermann Gletscher as measured from its grounding line at y=0 km. Triangles are observations while lines indicate a steady 1 km per year advance. The insert shows three maps of observed glacier shapes. From Muenchow et al., 2014.

Back in 2003 the glacier advanced about 1 km each year and it does so still. Almost the same, but not exactly, because the removal of 6 “Manhattans” in 2010 and 2012 increased the forward speed some, that is, the glacier now moves faster forward than it did before. Many sensors placed on the glacier measured this speeding, but the glacier also gets thinner as it speeds up. It is stretched thin. I published this back in 2016 together with Drs. Laurie Padman, Keith Nicholls, and my PhD student Peter Washam in Oceanography:

Muenchow2016_03

Speed at which Petermann Gletscher moves out into the sea from many different measurements. The glacier moves more slowly over land (negative distances) than it does floating over the ocean (positive distances). Estimates made after 2012 are about 10-20 % higher than RADARSAT estimates before that date. From Muenchow et al., 2016.

With substantial help from the British Antarctic Survey we installed in 2015 a small ocean observing system under the floating glacier. It transmitted data from 800 meters (2400 feet) below the 100 m (300 feet) thick glacier ice via cables connected to a weather station. We sucessfully repaired the station (as well as a Danish weather station nearby) that stopped transmitting data via satellites in 2016. Two journalists of the Washington Post, Chris Mooney and Whitney Shefte joined Keith Nicholls and myself. Their outstanding and accurate reporting of our work includes video and graphics for a wider audience that you can find at this link:

Washington Post Video of 2016 Petermann Gletscher Site Visit

The ocean and glacier data were worked over carefully by Peter Washam who defended his dissertation last month. Dr. Washam moved to Georgia Tech in Atlanta to work with Dr. Britney Schmidt whose interests relate to the ice-covered oceans below some moons of Jupiter. Peter connected ocean temperature and salinity with ice radar and remote sensing data to estimate how much the glacier is melted by the ocean and how the ocean does this. His main result will be published later this year in the Journal of Glaciology [Added July-12, 2019: Published online as Washam et al., 2019 at the Journal of Glaciology.], that is

“… This increase in basal melt rates confirms the direct link between summer atmospheric warming around Greenland and enhanced ocean-forced melting of its remaining ice shelves. We attribute this enhanced melting to increased discharge of subglacial runoff into the ocean at the grounding line, which strengthens under-ice currents and drives a greater ocean heat flux toward the ice base…”

The next large calving will be no surprise: Large fractures cross much of the glacier. They are visible about 10-20 km behind the current terminus and are discussed and closely monitored almost every day at the excellent site of Greenland Enthusiasts from all walks of life who post at

https://forum.arctic-sea-ice.net/index.php/topic,53.600.html

Furthermore, a new sophisticated computer model of Petermann Gletscher reveals that the loss of this large “still attached” ice island is already gone from the glacier in terms of the friction that it provides along the sidewalls. Another way of putting this, all it takes is a little wiggle or bump and the separation will become visible. Dr. Martin Rueckamp just published this study in the Journal of Geophysical Research.

There is much more to be explored with regard to Petermann. Here are some of the readings and writings that I have done with many fellow sailors through uncertain climates:

Johnson, H.L., A. Muenchow, K.K. Falkner, and H. Melling: Ocean circulation and properties in Petermann Fjord, Greenland. Journal of Geophysical Research, 116, doi:10.1029/2010JC006519, 2011. .pdf

Muenchow, A., L. Padman, and H.A. Fricker: Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012 Journal of Glaciology, 60, doi:10.3189/2014JoG13J135, 2014. .pdf

Muenchow, A., L. Padman, P. Washam, and K.W. Nicholls, 2016: The ice shelf of Petermann Gletscher, North Greenland and its connection to the Arctic and Atlantic Oceans, Oceanography, 29, 84-95, 2016. .pdf

Rueckamp, M, N. Neckel, S. Berger, A. Humbert, and V. Helm: Calving induced speed-up of Petermann Glacier, Journal of Geophysical Research, 124, 216-228, 2019. .pdf

Shroyer, E., L. Padman, R. Samelson, A. Muenchow, and L. Stearns: Seasonal control of Petermann Gletscher ice-shelf melt by the ocean’s response to sea-ice cover in Nares Strait, Journal of Glaciology, 63, doi:10.1017/jog.2016.140, 2017. .pdf

Washam, P., A. Muenchow, and K.W. Nicholls: A decade of ocean changes impacting the ice shelf of Petermann Gletscher, Greenland, Journal of Physical Oceanography, 48, 2477-2493, 2018. source

Washam, P., K.W. Nicholls, A. Muenchow, and L. Padman: Summer surface melt thins Petermann Gletscher ice shelf by enhancing channelized basal melt, Journal of Glaciology, 65, doi:10.1017/jog.2019.43, 2019. .pdf

How to whisper under sea ice: Wireless Acoustic Sensor Network Design

I want to build a cell phone system under water. I want it to send me a text messages every 30 minutes from 200 feet below the ocean that is covered by sea ice next to a glacier in northern Greenland where polar bears roam to catch seals for food at -40 Fahrenheit. Why would I want to do this and is this is even possible?

The author measuring sea ice thickness in Wolstenholme Fjord, Greenland April-17, 2017.

The author measuring sea ice thickness in Wolstenholme Fjord, Greenland April-17, 2017.

Our project successfully showed that it is possible to move data as text messages from a computer in the ocean to another and on to another and then via a cable to a weather station and then on to a satellite and then on to my laptop at home somewhere, anywhere, really [Intellectual Merit]. The ocean data that we moved by whispering from modem to modem (my acoustic cell phone towers) under water can be anything that any scientist may want to study. It could, for example, detect pollutants in the water that seep out of the sediment like gas or oil or radioactive materials burried accidentally [Broader Impacts] such as a nuclear-tipped B-52 bomber that crashed into Wolstenholme Fjord on January-21, 1968 at the height of the Cold War. The propagation of sound under ice also has military applications, because our communication network operates in both ways, that is, if I can receive a text message, I can also send one [Broader Impacts].

Installation of Automated Weather Station on Mar.-23, 2017 near Thule, Greenland via snowmobile. The station includes a satellite connection to the internet and a cable to the ocean.

Installation of Automated Weather Station on Mar.-23, 2017 near Thule, Greenland via snowmobile. The station includes a satellite connection to the internet and a cable to the ocean.

While the problem sounds simple enough, it is hard, real hard, because it requires many different people with very different skill sets. Our project included mechanical, electrical, and computer engineers but also scientists who know about acoustics, oceanography, and sea ice, as well as technicians with common sense and practical abilities to keep machines and people moving and running safely. This includes guns that we had to carry while working on the sea ice via snowmobile to protect from polar bears and medically trained personnel who could spot frostbites before they bite. All of this has to come together in just the right way and right time. Good and successful science is more than just engineering and machines, there is a strong human element in all polar field work such as ours. 

A local volunteer is designing, building, and rigging the Research Sled R/S Peter Freuchen for profiling the ocean below the sea ice in March 2017 on Thule Air Base.

A local volunteer is designing, building, and rigging the Research Sled R/S Peter Freuchen for profiling the ocean below the sea ice in March 2017 on Thule Air Base.

The first step in our project involved the design of the acoustic modems that Lee Freitag of Woods Hole Oceanographic Institution did many years back. It took us about 2 years to select this design that Lee then modified for this application in 2014-15). The second step involved the selection of a study site where our small group of 6 people could work and experiment and learn by some trial and error without incurring extra-ordinary costs (2015-16). It helped that I was in and out of Thule Air Base on unrelated projects in 2015 and 2016 when we settled for the final experiment to take place in March and April of 2017. Satellite remote sensing tools where then developed to quantify sea ice conditions for safe operation and navigation traveling on the  ice. We uncovered a barely visible area of thin ice to the south of Manson Island that recurs at the same location every year. We stayed clear of this area.

Thule2017_CTD

Satellite image of ice-covered Wolstenholme Fjord, Greenland with water column profiling station (green dots) and acoustic modems (red dots). Blue lines are water depths in meters. Labels G1, G2, and G3 indicate three tide-water glaciers while Thule refers to Thule Air Base. Saunders Island is near the center left while the weather station is the red dot halfway between Saunders and Manson Islands.

Field work started with a survey of sea ice thickness on Mar. 18/19, 2017 by drilling 2” holes through the sea ice that varied in measured thickness from 0.12 m (4 inches) near Manson Island to 1.25 m (4 feet) near Thule Air Base. On Mar.-23, 2017 we deployed the weather station along with a tent and survival gear at the center of our study area. An ocean temperature mooring was deployed to complement in time a spatial survey of ocean sound speed profiles estimated from conductivity, temperature, depth (CTD) measurements. We drilled 10” holes through the sea ice for our profiling CTD operated via an electrical winch. Our CTD survey spanned the entire fjord from three tidewater glaciers in the east to the edge of the sea ice in the west. Concurrently ocean testing of acoustic communication between modems commenced Apr.-8, 2017 and the final array was deployed Apr.-14/15 to be fully operational Apr.-16/18. All gear was recovered and stored at Thule Air Base Apr.-18/19, 2017 before our departure Apr.-20, 2017.

Research Sled

Research Sled “Peter Freuchen” with wooden CTD storage box, electrical winch, tripod, and electrical motor during deployment on Apr.-7, 2017. View is to the west with Cape Atholl on the left and Wolstenholme Island on the right background. University of Delaware technician operates the winch via joy stick while a student monitors the instrument’s descent through water column visually at the 10” hole and acoustically via a commercial Fish-Finding sonar.

Subsequent analysis in 2017/18 revealed a successful experiment as data from ocean sensors traveled along multiple paths to the weather station and on to the internet. All data were submitted to the NSF Arctic Data Center where after review they will become public at

https://arcticdata.io/catalog/view/urn:uuid:d2775281-3231-47d0-ab79-b2e506ea8d04

This graph is just one of many in desperate need of a proper peer-reviewed publication. There is always more work to do …

Time series of ocean temperature at the weather station from 10-m (top) to 100-m (bottom below the sea ice. The red line gives the -1.7 Celsius for reference. The temperature field dominates the speed of sound field. Note the presence and absence of tidal oscillations.

Time series of ocean temperature at the weather station from 10-m (top) to 100-m (bottom below the sea ice. The red line gives the -1.7 Celsius for reference. The temperature field dominates the speed of sound field. Note the presence and absence of tidal oscillations.

Germany 1985 to 2018

I left my native Germany in 1985 to study oceanography in North Wales. I returned in 2018 as an American Professor of polar oceanography.  

  Much has changed in 33 years. For one, the divided country that I left is no more. The largely peaceful unification of Germany and Europe removed barbed wires, concrete walls, and shoot-to-kill orders along a violent border. The Cold War was over, I saw the scenes of joy on TV in a bar in Newark, Delaware more than 4100 miles (5600 km) away:

https://abcnews.go.com/Archives/video/nov-10-1989-celebration-berlin-wall-8980622

I experienced the “new” Germany for the first time when sailing aboard Germany’s icebreaker R/V Polarstern in 2014 to deploy ocean moorings. At the time I counted four distinct German cultures.  

  Today is a national holiday that celebrates the “Tag der Deutschen Einheit” or “Day of German Unity.” It is very much work in progress as Germany is becoming more diverse with its over 10 Million people born in countries other than Germany. Turkey (1.5 Mil), Poland (0.9 Mil), and Syria (0.7 Mil) field the most foreign-born people as of 2017. From my American perspective Germany has become a more normal country with its recent politics, troubles, inconveniences, and strengths that these diverse backgrounds entail.

Dragonfly and I arrived in Bremerhaven three months ago to live and work here for at least a year. It took us two days to get bicycles and another two days to find a well-furnished apartment. My parents visited the second weekend and we became Bremerhaven tourists for two days. We purchased the required catastrophic health insurance from a credible company for about €550/year each, but after 3 months we are still waiting for the installation of an internet connection at our home, but we are hopeful that this may change soon.

Author aboard German research vessel F/S Maria S. Merian in port of Longyearbyen, Svalbard in the fall of 2018. [Photo by Dragonfly Leathrum.]

Author aboard German research vessel F/S Maria S. Merian in port of Longyearbyen, Svalbard in the fall of 2018. [Photo by Dragonfly Leathrum.]

 

Northern Winds and Currents off North-East Greenland

I spent 6 weeks aboard the German research icebreaker R/V Polarstern last year leaving Tromso in Norway in early September and returned to Bremerhaven, Germany in October. We successfully recovered ocean sensors that we had deployed more than 3 years before. It felt good to see old friends, mates, and sensors back on the wooden deck. Many stories, some mysterious, some sad, some funny and happy could be told, but today I am working on some of the data as I reminisce.

The location is North-East Greenland where Fram Strait connects the Arctic Ocean to the north with the Atlantic Ocean in the south. We worked mostly on the shallow continental shelf areas where water depths vary between 50 and 500 meters. The map shows these areas in light bluish tones where the line shows the 100 and 300 meter water depth. Fram Strait is much deeper, more than 2000 meters in places. I am interested how the warm Atlantic water from Fram Strait moves towards the cold glaciers that dot the coastline of Greenland in the west.

Map of study area with 2014-16 mooring array in box near 78 N across Belgica Trough. Red triangles place weather data from Station Nord (81.2 N), Henrik Kr\o yer Holme (80.5 N), and Danmarkhaven (76.9 N). Black box indicates area of mooring locations.

There is also ice, lots of sea icebergs, and ice islands that we had to navigate. None of it did any harm to our gear that we moored for 1-3 years on the ocean floor that can and often is scoured by 100 to 400 meter thick ice from glaciers, however, 2-3 meter thick sea ice prevented us to reach three mooring locations this year and our sensors are still, we hope, on the ocean floor collecting data.

Ahhh, data, here we come. Lets start with the weather at this very lonely place called Henrik Krøyer Holme. The Danish Meteorological Institute (DMI) maintains an automated weather station that, it seems, Dr. Ruth Mottram visited and blogged about in 2014 just before we deployed our moorings from Polarstern back in 2014:

Weather station on Henrik Kroeyer Holme [Credit: Dr. Ruth Mottram, DMI]

It was a little tricky to find the hourly data and it took me more than a day to process and graph it to suit my own purposes, but here it is

Winds (A) and air temperature (B) from an automated weather station at Henrik Kroeyer Holme from 1 June, 2014 through 31 August, 2016. Missing values are indicated as red symbols in (A).

The air temperatures on this island are much warmer than on land to the west, but it still drops to -30 C during a long winter, but the end of July it reaches +5 C. The winds in summer (JJA for June, July, and August) are weak and variable, but they are often ferociously strong in winter (DJF for December, January, February) when they reach almost 30 meters per second (60 knots). The strong winter winds are always from the north moving cold Arctic air to the south. The length of each stick along the time line relates the strength of the winds, that is, long stick indicates much wind. The orientation of each stick indicates the direction that the wind blows, that is, a stick vertical down is a wind from north to south. I use the same type of stick plot for ocean currents. How do these look for the same period?

Ocean current vectors at four selected depths near the eastern wall of Belgica Trough. Note the bottom-intensified flow from south to north. A Lanczos low-pass filter removes variability at time scales smaller than 5 days to emphasize mean and low-frequency variability.

Ocean currents and winds have nothing in common. While the winds are from north to south, the ocean currents are usually in the opposite direction. This becomes particular clear as we compare surface currents at 39 meters below the sea surface with bottom currents 175 or even 255 meters below the surface. They are much stronger and steadier at depth than at the surface. How can this be?

Image of study area on 15 June 2014 with locations (blue symbols) where we deployed moorings a few days before this satellite image was taken by MODIS Terra. The 100-m isobath is shown in red.

Well, recall that there is ice and for much of the year this sea ice is not moving, but is stuck to land and islands. This immobile winter ice protects the ocean below from a direct influence of the local winds. Yet, what is driving such strong flows under the ice? We need to know, because it is these strong currents at 200 to 300 meter depth that move the heat of warm and salty Atlantic waters towards coastal glaciers where they add to the melting of Greenland. This is what I am thinking about now as I am trying to write-up for my German friends and colleagues what we did together the last 3 years.

Oh yes, and we did reach the massive terminus of 79 North Glacier (Nioghalvfjerdsfjorden) that features the largest remaining floating ice shelf in Greenland:

We recovered ocean moorings from this location also, but this is yet another story that is probably best told by scientists at the Alfred-Wegener-Institute who spent much time and treasures to put ship, people, and science on one ship. I am grateful for their support and companionship at sea and hopefully all of next year in Bremerhaven, Germany.

Two Years Ocean Observing Below Petermann Glacier Greenland

A year ago today I last set foot on Petermann’s floating ice shelf. The 28th of August 2016 was a drizzly, cloudy day with water running over the surface of the glacier in small streams emptying into larger streams to form small rivers that merged into larger channels carved into the ice. Two years ago Keith Nichols and I set-up a weather station atop the glacier. Many friends helped. We connected copper wires, ocean sensors, and a surface station to collect data from sensors 100-m below the ice in 800-m deep water. The small 2015 project of opportunity keeps giving us hourly ocean data. I am still stunned by our luck and technology.

My Petermann story started in 2010 when a first Manhattan-sized ice cube broke off the glacier. Two days after a University of Delaware press release, the US Congress asked me to appear before one of its inquiring committees. I humbly acknowledged how little I knew then, but everyone else knew even less. In 2012 another Manhattan-sized glacier piece broke off. While satellite a image shows what happens, only hard ocean data and modeling explains why it happens. Two research proposals were rejected, sadly, to probe ocean physics with carefully designed experiments, but in 2016 Alan Mix invited me to an expedition to Petermann aboard the Swedish icebreaker Oden. I gladly accepted, but I wanted to contribute something. That “something” became the Petermann Glacier Ocean Weather Observatory.

Alan needed holes drilled through the 100-m to 400-m thick glacier. Actually, he needed mud from 800 meters below the glacier. Keith Nichols of the British Antarctic Survey drilled those holes for Alan and collected the mud. My plan was to recycle the hole, that is, we dropped kevlar line, copper wire, and ocean sensors into the ocean and connected all to a weather station. David Huntley and I designed the system that included an Iridium satellite phone. Iridium phone calls ceased in February 2016, but a “service call,” that is, a helicopter site visit fixed the station. Chris Mooney and Whitney Shefte told the story for the Washington Post on 30 December 2016.

Ocean temperature at 95-m, 300-m, and 450-m below the sea surface as well as pressure at the bottom sensor near 810-m depth (~810 dbar pressure) updated through 27 August 2017.

The graph shows the entire 2-year long data record. Each gray vertical bar indicates a month between July 2015 and December 2017. The top record shows ocean temperatures just below the floating glacier ice. It was a surprise to see the data change from -0.3 Celsius to -1.6 degrees Celsius. The latter is close to the freezing point of salt water. Hence I interpret low-temperature events as meltwater pulse that swoosh past our sensor.

At 300-m we find a smaller range of temperatures near +0.1 degrees Celsius. Note the steady increase of temperature. Fluctuations are similar, but their absolute values increase with time. The linear warming trend becomes clear at 450-m depth, because the fluctuations diminish, but the warming does not. Temperatures at all depths increased over the entire two years of hourly observations.

The pressure record of the bottom-most sensor on the kevlar line perplexes me: During the first year the sensor slides into deeper water, because the kevlar stretches as all lines do when weighted down. In July 2016 the sensor sharply rises by almost 3 meters from 810.5 to 808.5 dbar to just as rapidly drop again to the 810.5 dbar value. The same feature occurs in the summer of 2017 also. It relates to the summer melt season, but how? I do not know.

The 2-year record is not perfect as the many gaps indicate. These result from electronic and mechanical failures that, I feel, are caused by long and harsh winters when temperatures dropped below -40 degrees Celsius or Fahrenheit. These cold temperatures challenge the best batteries during the 4-5 months of total darkness. On 20. December 2016 our batteries ran out and shut down the station. The sun revived our data gathering when the solar panels recharged batteries in March 2017.

The glacier also melts about 1-2 meters at the surface each summer. This surface melt tilted and almost crashed the station that we repaired last year today. In 2015 we had 2-m of pipe to fix into the glacier ice. In 2016 we replaced this with a 4-m pole that should survive two year’s of surface melt, I hope.

There are many, many people who all contributed in ways both small and large. It takes a village to raise a station on Greenland: