Tag Archives: moorings

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:

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/

Preparing Ocean Work outside Thule Air Base

I am heading to North Greenland in 3 days time to work where temperatures will be close to -20 F. The ocean is covered by 3-4 feet of sea ice that is frozen to land. We will drill lots of ice holes to deploy ocean sensors that will connect via cables to weather stations and satellite phone. Fancy $20,000 GPS units will measure the tides across the fjord and provide a group of future Naval officers a reference for their fancy electronic gear to measure sea ice thickness remotely by walking and comparing results to those obtained from planes overhead. Cool and cold fun.

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The ocean pier at Thule Air Base in Greenland in March 2017. The view is towards the north-west along my proposed mooring line [Photo Credit: Sean Baker]

There has been much packing and shipping the last weeks, about 2300 lbs to be precise,which made my body stiff and sore. Another way to hurt my aging body was to learn shotgun shooting for the unlikely polar bear encounter on the sea ice. My shoulder still hurts from the recoil blasts of the 12 gauge pump-action gun with 3” long cartridges that included a 1 oz. lead slug. I also tested a cot and sleeping bag that will be with me on the ice for emergencies. The night in my garden a few days ago was cozy, but the cot required an insulation mattress, as it was too close to the ground. It was rough sleeping, because of unexpected noises not cold, but I did sleep some and woke up when the sun came up.

Cot, air mattress, and down sleeping bag testing in my garden after a rough night.

Cot, air mattress, and down sleeping bag testing in my garden after a rough night.

The clear skies over Thule during the 2 weeks that the sun is up again also gave me the first Landsat image. It shows the landfast sea ice, but it also shows its very limited extend as very thin ice and perhaps even open water occurs while the winds blow along the coast from the north. This cold wind moves the mobile sea ice offshore to the west thus opening up the oceans that will promptly freeze, however, the back ocean still shows under the inch-thin new ice:

Wolstenholme Fjord as seen by LandSat on Feb.-27, 2017. The line with the red dots extends from Thule pier seaward towards the north-west. Note the dark spot near the left-top corner that shows thin new ice or even open water. White contours are ocean depths in meters.

Wolstenholme Fjord as seen by LandSat on Feb.-27, 2017. The line with the red dots extends from Thule pier seaward towards the north-west. Note the dark spot near the left-top corner that shows thin new ice or even open water. White contours are ocean depths in meters.

This thin new ice is the limit of where I expect to be working. After measuring ice thickness directly via drilling through the ice, my first measurement will be that of how temperature and salinity varies from under the ice to the bottom of the ocean.

Working on the sea ice off northern Greenland [Photo credit, Steffen Olsen]

Working on the sea ice off northern Greenland [Photo credit, Steffen Olsen]

Danish friends do this routinely about 60 miles to the north where they work out of the Inughuit community of Qaanaaq, but Inglefield Fjord is much deeper and connects to warm Atlantic waters from the south that, I believe, we do not have in Wolstenholme Fjord. Hence I expect much less heat inside Wolstenholme Fjord and perhaps a different response of three glaciers to ocean forcing. This theory does not help me much as I will have to lower instruments via rope and a winch into the water. How to attach rope to instruments and winch? Knots.

I am very poor at making knots as my hand-eye co-ordination and memory is poor. So I spent some time this week to learn about knots such as

that should work on my braided Kevlar lines that I connect to shackles

Fancy knots on shackles in my home office ... yes, Peter Freuchen is on the bookshelf, too.

Fancy knots on shackles in my home office … yes, Peter Freuchen is on the bookshelf, too.

There are always devils in the many details of field work. Another worry is that my 10” ice-drill is powered by 1 lbs bottles of propane. It is not possible to send these camping propane canisters via air, but larger 20 lbs tanks exist in Thule for grill cooking at the NSF dormitory where I will be staying. So I also will have to learn how to fill the smaller container from the large one. Just ordered another adaptor from Amazon to travel with me on my body to do this.

I am both terribly nervous and excited about the next 6 weeks. This is my first time working on the ice, because before I have always been on icebreakers in summer. These past Arctic summer expeditions on ships created an unreal and distant connection that, I hope, will be shattered by this spring. I will get closer to the cold and icy seas that are my passion. Oceanography by walking on water … ice.

Sea Ice from Satellite at 20-m Resolution

I am a self-taught amateur on remote sensing, but it tickled my pride when a friend at NASA asked me, if I could tell a friend of his at NOAA on how I got my hands on data to produce maps of radar backscatter to describe how the sea ice near Thule Air Base, Greenland changes in time and space.

Wolstenholme Fjord, Greenland Feb.-5, 2017 from Sentinel-1 radar. The data are at 20-m resolution

Wolstenholme Fjord, Greenland Feb.-5, 2017 from Sentinel-1 radar. The data are at 20-m resolution

In about 4 weeks from today I will be working along a line near the red dots A, B, and C which are tentative locations to place ocean sensors below the sea ice after drilling through it with ice fishing gear. The colored line is the bottom depth as it was measured by the USCG Healy in 2003 when I was in Thule for the first time. Faint bottom contours are shown in gray.

I discovered the 20-m Sentinel-1 SAR-C data only 3 weeks ago. They are accessible to me (after making an account) via

https://scihub.copernicus.eu/dhus/#/home

where I then search for a specific geographic area and time frame using the following “product”

Product Type: GRD
Sensor Mode: IW
Polarization: HH

Screenshot on how I search for the Sentinel-1 SAR-C DATA.

Screenshot on how I search for the Sentinel-1 SAR-C DATA.

The more technical detail can be found at

https://sentinel.esa.int/web/sentinel/user-guides/sentinel-1-sar

where one also finds wonderful instructional videos on how to work the software.

The data file(s) for a typical scene are usually ~800 MB, however, for processing I use the free SNAP software (provided by European Space Agency) via a sequence of steps that result in a geotiff file of about 7 MB.

Screenshot of SNAP software and processing with [1] input and [2] output of the Feb.-5, 2017 data from Wolstenholme Fjord.

Screenshot of SNAP software and processing with [1] input and [2] output of the Feb.-5, 2017 data from Wolstenholme Fjord.

This .tiff file I then read with Fortran codes to tailor my own (quantitative or analyses) purposes.

Start of Fortran code to covert the SNAP output geotiff file into an ascii file with latitude, longitude, and backscatter as columns. The code has 143 lines plus 80 lines of comment.

Start of Fortran code to covert the SNAP output geotiff file into an ascii file with latitude, longitude, and backscatter as columns. The code has 143lines plus 80 lines of comment.

The final mapping is done with GMT – General Mapping Tools which I use for almost all my scientific graphing, mapping, and publications.

Please note that I am neither a remote sensing nor a sea-ice expert, but consider myself an observational physical oceanographer who loves his Unix on a MacBook Pro.

Working the Night shift aboard CCGS Henry Larsen in the CTD van in Aug.-2012. [Photo Credit: Renske Gelderloos]

Working the Night shift aboard CCGS Henry Larsen in the CTD van in Aug.-2012. [Photo Credit: Renske Gelderloos]

If only my next problem, working in polar bear country with guns for protection, had as easy a solution.

Polar bear as seen in Kennedy Channel on Aug.-12, 2012. [Photo Credit: Kirk McNeil, Labrador from aboard the Canadian Coast Guard Ship Henry Larsen]

Polar bear as seen in Kennedy Channel on Aug.-12, 2012. [Photo Credit: Kirk McNeil, Labrador from aboard the Canadian Coast Guard Ship Henry Larsen]