Category Archives: Thule

Greenland Glacier-Driven Ocean Circulation

Greenland’s coastal glaciers melt, shrink, and add to globally rising sealevel. They also drive local ocean currents that move icebergs around unless they are stuck on the bottom. The glaciers’ melt is cold fresh water while the adjacent ocean is both salty and warm. Checking on what we may expect against observations, I here use data from NASA’s Ocean Melts Greenland initiative that dropped ocean probes from an airplane into the ice waters off coastal Greenland to measure ocean temperature and salinity.

For six years these data show how the coastal ocean off Greenland varies from location to location next to glaciers as well as from year to year. More specifically, I picked Melville Bay in North-West Greenland for both its many glaciers and many dropped NASA ocean sensors. The ocean data allow me to estimate ocean currents by using a 100 year old physics method. I just taught this to a small class of undergraduate science students at the University of Delaware. My students are strong in biology, but weak on ocean physics. This essay is for them.

Melville Bay is a coastal area off north-west Greenland between the town of Upernavik (Kalaallisut in Greenlandic) near 73 N latitude where 1100 people live and the village of Savissivik (Havighivik in Inuktun) at 76 N latitude where 60 Inuit live. There are no other towns or settlements between these two villages that are about as far apart as Boston is from Philadelphia, PA. Imagine there were no roads from Boston to New York to Philadelphia but only one large glacier next to another large glacier. This is Melville Bay.

Below I show an excellent set of photos of Savissivik by a French husband and wife team who visited in 2013/14. Their photographic gallery captures elements of contemporary subsistence living in remote Greenland where animals like seals, birds, fish, narwhal, and polar bears provide food, fuel, clothing, and income.

NASA dropped some 50 ocean sensors into Melville Bay froma plane during the short summer seasons each year 2016 through 2021. I met NASA pilots, engineers, and scientists doing their experiments when I was doing mine from a snowmobile in April of 2017 and again with Danish friends from a Navy ship in August of 2021, but these are stories for another day.

Let me start with a map of where NASA dropped their ocean profiling floats into Melville Bay and thus introduce the data. While the surface waters are usually near the freezing point, waters 300-400 meters deep down are much warmer. They originate from the Atlantic Ocean to the south and one of the goals of NASA’s “Ocean Melts Greenland” campaigns was to determine if and how these Atlantic waters reach the coastal glaciers. Most glaciers of Melville extend into this warm ocean layer and thus are melted by the ocean.

In the map above I paint the maximal temperatures in red and the bottom depths in blue tones. The profile on the right shows data for all depths at one station. As salinity increases uniformly (red curve) the temperature increases to a maximum near 300-m depth (black curve). It is this maximal subsurface temperature that I extract for each station and then put on the contour and station map on the left. The straight blue line connects Upernavik in the south with Sassivik in the north. It is an arbitrary line, coast-to-coast cutting across Melville Bay.

The warmest warm waters we find near Upernavik in the south and within a broad submarine canyon that brings even warmer waters from Baffin Bay towards the coast. Temperatures here exceed 2.4 or even 2.7 degrees Celsius. Most coastal waters along Melville Bay have a temperature maximum of about 1.5 to 1.8 degrees Celcius (about 35 Fahrenheit) and this “warm Atlantic” ocean water melts the coastal glaciers. The ocean melts the glaciers summer and winter while the warm air melts it only in summer.

There is more, because the glaciers’ melt also discharge fresh water into the ocean where it mixes to to form a layer of less dense or buoyant water. The buoyant waters create a local sealevel that is a little higher along the coast than farther offshore. The map above indicates that this “little higher sealevel” comes to about 4 cm or 2 inches. If this pressure difference across the shore is balanced by the Coriolis force, as it often does, then an along-shore coastal current results. This coastal current would move all icebergs from south to north unless they get stuck on the bottom. Along the northern coastline of Melville Bay the surface flow is from east to west. The coastal current is strongest near Savissivik where we find a (geostrophic) surface current larger than 40 cm/s. At that speed an iceberg would move more than 21 miles per day. Such strong surface flows are exceptional and diminish rapidly with depth. Hence a freely floating iceberg with a draft of several hundred meters would move much slower than the surface current.

I met a hunter from Savissivik in April of 2017 and for a fast-moving night we discussed the state of local fishing, hunting, living, traveling, and working on the sea ice next to the glaciers of Melville Bay. He invited me to become his apprentice. As such I would now ask him about the surface currents outside his home. Which way does he observe the icebergs to move in summer or winter? Has hunting on the sea ice in winter changed over his life time? When is it safe to travel there with a dog-sled? Could he and I perhaps work together during the spring to deploy ocean sensors through the sea ice? I am dreaming again …

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.

Only in Thule Greenland

… do you find a machinist working metal to take photos while I do oceanography the old-fashioned way by pulling up 100 meters of kevlar line to recover an ocean probe.

Wolstenholme Fjord March-26, 2017. [Photo by Mogens Werth Christensen]

The data were subsequently used by ocean acousticians to test speed of sound propagation as part of an NSF project on testing an underwater communication system to move data from A to B via C or D. The automated weather station reports ocean temperature and saltiness as well at

http://ows.udel.edu/ice

Web-site is low-bandwidth to be used operationally by Air Force personnel in Greenland and local communities where internet access and speeds are severely limited.

Greenland Oceanography by Sled and Snowmobile

Wind chill matters in Greenland because one must see and breath. This implies exposed skin that will hurt and sting at first. Ignoring this sting for a few minutes, I notice that the pain goes away, because the flesh has frozen which kills nerves and skin tissue. The problem becomes worse as one drives by snowmobile to work on the sea ice which I do these days almost every day.

Navigating on the sea ice by identifying ice bergs with LandSat imagery. The imagery also shows polynyas and thin ice in the area. [Photo Credit: Sonny Jacobsen]

Mar.-22, 2017 LandSat image of study area with Thule Air Base near bottom right, Saunders Island in the center. Large red dots are stations A, B, and C with Camp-B containing weather station, shelter, and first ocean mooring. My PhD student Pat Ryan prepared this at the University of Delaware.

My companion on the ice is Sonny Jacobsen who knows and reads the land, ice, and everything living on and below it. He teaches me how to drive the snowmobile, how to watch for tracks in the snow, how to pack a sled, and demonstrates ingenuity to apply tools and materials on-hand to fix a problem good enough to get home and devise a new and better way to get a challenging task done. Here he is designing and rigging what is to become our “Research Sled” R/S Peter Freuchen, but I am a little ahead of my story:

Sonny Jacobsen on Mar.-27, 2017 on Thule Air Base building a self-contained sled for ocean profiling.

First we set up a shelter in the center of what will hopefully soon become an array of ocean sensors and acoustic modems to move data wirelessly through the water from point A in the north-west via point B to point C. Point C will become the pier at Thule Air Base while the tent is at B that I call Camp-B:

Ice Fishing shelter to the north-east of Saunders Island seen to the left in the background.

Next, we set up an automated weather station (AWS) next to this site, because winds and temperatures on land next to hills, glaciers, and ice sheets are not always the same 10 or 20 km offshore in the fjord. It is a risk-mitigating safety factor to know the weather in the study area BEFORE driving there for 30-60 minutes to spend the day out on the ice. It does not hurt, that this AWS is also collecting most useful scientific data, but again, I am slightly ahead of my story:

Weather station with shelter at Camp-B with the northern shores of Wolstenholme Fjord in the background. Iridium antenna appears just above the iceberg on the sidebar of the station. Winds are measured at 3.2 m above the ground.

With shelter and weather station established and working well, we decided to drill a 10” hole through 0.6 m thin ice to deploy a string of ocean instruments from just below the ice bottom to the sea floor 110 m below. Preparing for this all friday (Mar.-24), we deploy 22 sensors on a kevlar line of which 20 record internally and must be recovered while 2 connect via cables to the weather station to report ocean temperature and salinity along with winds and air temperatures. It feels a little like building with pieces of Lego as I did as a kid. Engineers and scientists, perhaps, are trained early in this sort of thing.

Weather station with ocean mooring (bottom right) attached with eastern Saunders Island in the background on Sunday Mar.-26, 2017.

Sadly, only the ocean sensor at the surface works while the one at the bottom does not talk to me. I can only suspect that I bend a pin on the connector trying to connect very stiff rubber sealing copper pins from the cable with terminations equally stiff in the cold, however, there are other ways to get at the bottom properties albeit with a lot more effort … which brings me to R/S Peter Freuchen shown here during its maiden voyage yesterday:

R/S Peter Freuchen in front of 10” hole (bottom right) for deployment of a profiling ocean sensor. The long pipes looking like an A-frame on a ship become a tripod centered over the hole with the electrical winch to drive rope and with sensors (not shown) over a block into the ocean. This was yesterday Mar.-28, 2017 on the way from Camp-B back to Thule Air Base.

The trial of this research sled was successful, however, as all good trials, it revealed several weaknesses and unanticipated problems that all have solutions that we will make today and tomorrow. The design has to be simple to be workable in -25 C with some wind and we will strip away layers of complexities that are “nice to have” but not essential such as a line counter and the speed at which the line goes into the water. There can not be too many cables or lines or attachments, because any exposure to the elements becomes hard labor. This becomes challenging with any gear leaving the ocean (rope, sensors) and splattering water on other components. Recall that ocean water is VERY hot at -1.7 C relative to -25 C air temperatures. This means that ANYTHING from the ocean will freezes instantly when in contact with air. Efficiency and economy matter … as does body heat to keep critical sensors and batteries warm.

A big Thank-You to Operation IceBridge’s John Woods for something related to this post that I wish not to advertise 😉

Travels to Greenland in Winter

Waking up after 5 hours on a plane from Baltimore, Maryland to Thule, Greenland large white Pitugfik Gletscher distinguishes itself from the white sea ice by its ragged snout as the plane approaches my new home for the next 6 weeks. I am traveling with 9 midshipmen of the US Naval Academy of which two are women, their 4 professors, and bear guard from Alaska. We will be working and living together for the next 7 days.

Pitugfik Glacier during the early morning hours of Mar.-9, 2017.

A little further along the coast we enter Wolstenholme Fjord where from the plane wide cracks of open water stand out as black against the bluish white horizon. This will be the outer margin of where I plan to work the ice and ocean underneath the next 6 weeks. We need to stay on the shore side of this transition of land-fast to mobile sea ice. I have watched this boundary for the last 4 months with satellite imagery, but seeing with my own eyes is an entire different and humbling experience.

Sea ice near Kap Atholl with heads of open water that separate land-fast ice that does not move from mobile ice.

We land safely at the airport, get our passport stamped by Danish officials, pick up our luggage, and are received by wonderful people working for both NASA and the National Science Foundation. After a hearty lunch of dark rye bread and my beloved pickled herrings christmas arrives in the form of many carefully wrapped packages: I try to find my Arctic clothing that I shipped months before. It is much-needed as the -33 C take your breadth away. I also find the 2,500 lbs of science gear, some of which had arrived directly from Canada after it was ordered Dec.-10, 2016: Without this $22,000 electrical winch, I would be hard pressed to send sensors to the bottom of the ocean and back. Everything appears to be in place and fine, but some acoustic gear is still missing as its large lithium batteries need diplomatic clearances which takes a little longer. Perhaps they will be on the plane that is about to land. There is only 1 flight per week that connects Thule to the US. Hence advance planing is needed and those lithium batteries are not needed until April 6 when Lee and Taylor arrive from Massachusetts.

Where in this pile are my snow boots? Palletized gear on arrival in Thule Greenland.

The next day we put some of our gear out to measure how thick the sea ice is near the coast. While drilling a hole requires power tools, the ice is actually cut by a razor-sharp drill bit that is sensitive to damage when it refuses to cut the ice and no amount of force available can force it through the 3-4 feet of ice we find. We all learn the hard way when we accidentally drill into the frozen sea bed without finding any water. One drill bit down, we only got 2 more and are much, much more careful with it. The remaining drill bits have to last for the next 6 weeks … actually, they do not, because I can change the blades should one bit become dull. [I did not tell this the Naval Academy guys who were doing much of this drilling to support NASA’s Operation IceBridge.]

And on this note, I am heading out to sea at 7:59 am to drill one more hole to prepare for a first mooring deployment. A wooden stick without sensors attached will simulate a mooring that I want to recover after it is frozen in. More later …

P.S.: More photos and stories on this week’s adventures can be found at

https://www.facebook.com/USNAPolarScienceProgram/