Tag Archives: Nares Strait

Rules of Engagement: Ships, Science, and Democracy

The FS Polarstern will leave port tomorrow night for scientific work between Greenland and Spitsbergen near 79 degrees north latitude about 1200 km or 770 miles from the North Pole. It will be hard work, as there is more ice in Fram Strait than any other area that I sailed into the past 20 years. The early June departure date is the cause not a changing climate. I am usually home during the birthday of my wife this week and our wedding anniversary next week as usually my work does not get me into the Arctic until the end of July, but this year is different.

As on all ships everywhere, the rules of engagements, the daily cycle of life, the access to friends, family, and the news cycle change once at sea. Some things one leaves gladly behind such as dirty laundry, washing dishes, and cutting the lawn, while others are a little harder to let go such as a blooming garden, growing children, riding bicycles, and open internet connectivity. The latter does not fit romantic notions of life at sea, but a button on my jumper says “Geek” for a reason. Furthermore, I found the button in an ammunition box in the woods near my hometown while geocaching with my wife of 20 year; Mary Ann, I miss you.

The ship is afloat, loaded, and a new set of rules now applies about how one lives aboard. This is my last post that will not be approved by the Captain, the Chief Scientist, and/or one of their designated representatives. This is a perfectly acceptable, reasonable, and normal way to do business, because the ship represents more that just one perspective of one writer with one national or one educational background. Every ship has a mission and there are formal ways to report on those. Blogging is not one of them, but public outreach, education, and perhaps serving a greater public good is. Once at sea, the Captain’s rules of engagement are absolute on any ship anywhere for good reason.

Hence ships are not democratic institutions, but authority, command, and accountability are all vested in one person, the Captain. Ships such as the FS Polarstern do represent democratic societies, cultures, and values rather well on a time scale longer than a news or blog cycle. Furthermore, fun stuff happens anyway and may not need reporting in gory detail: over breakfast today, we had six scientists sitting together from six countries with divergent perspectives on issues ranging from ice algae and ocean currents to gun and tax laws. Most of us had never heart of each other, because we all represent diverse disciplines such as biology, chemistry, meteorology, or physics. Diversity is both fun and strength; nothing is more boring than everyone looking or thinking the same about religion, politics, or science.

There exists, I believe, an analogy between the non-democratic character of ships and the non-democratic character of science. On ships as in science the majority does not rule or decide what is right and what is wrong; a committee may vote and advise on how monies are allocated, but no committee decides on what is and what is not accepted truth. The data we collect, the though experiments we codify, the observations we simulate, and the predictions we make, all these are facts that test our ideas, that scrutinized our theories, and that show what is most likely to happen from a multitude of scientists of diverse training and background. Yet an essential part of this process is that the data must be shared, the results must be published, the publication must withstand scrutiny all according to democratic rules such as fair play, checks and balances, and transparency, however, the process itself is not democratic.

So, where does this leave me now? I move my mind towards being at sea where a different set of rules applies. Uncertainty exists on what can and what cannot be written and published on what schedule. There need not be a design to limit or censure communication, but Ocam’s Razor applies: People aboard work tirelessly at almost all hours of the day, those with command authority are burdened with multiple, often contradictory demands, or internet access off Greenland is so severely limited that only ice-charts and data for navigation reach the ship.

I love to write, share, edit, and think. And if the blogging does not work the next few weeks, some other form to share excitement and results will eventually find its way, as it always does. The path is the goal.

P.S.: Happy Birthday and Anniversary, Mary Ann und einen wunderschoenen Achtzigsten, Vati. Ich denke an Euch all, I am thinking of you all ;-)

Measuring Ice Thickness From The Ocean

Ice floats and moves abouts. It melts in summer, it freezes in winter, but it moves from here to there driven by winds and currents. Some ice leaves the Arctic Ocean via Fram Strait to the east of Greenland and some leaves via Nares Strait to the west of Greenland. For the last 11 years I worked with Canadian friends in Nares Strait, but this summer I will work on the other side of Greenland with German, Polish, and perhaps Norwegian colleagues in Fram Strait. This opportunity already helps me solve puzzles in Nares Strait and more generally how ocean currents around Greenland impact ice cover, thickness, and flux.

Jonathan Poole in 2012 with ice profiling sonar hit by ice.

Jonathan Poole in 2012 with ice profiling sonar that was hit by ice.

One of our many instruments measures the thickness of ice. Our sensor package is moored on the ocean floor and quietly sends out a single ping every few seconds. Think of this ping as the sound you make when you tap your desk with a finger. The sound travels from the desk to your ear where you hear it, because your inner ear has a drum that picks up the vibrations that the taping makes when it hits your ear-drum. Well, our ice-profiling sonar sends out this ping that travels through the water to the ice above, bounces off the ice, and returns to our sensor. We then measure the time it takes for our ping to travel to the ice and back. If we know the speed of sound in the water, if we know the density of the water, if we know the pointing direction of the sonar, and if we know how much water is above our sensor, then we can estimate the thickness of the ice. The sketch below shows design details that go into keeping such a sensor system in the ocean recording data for 2-3 years at a time.

Sketch of ice-profiling sonar mooring deployed on the bottom of the ocean. Design by Dr. Humfrey Melling of Fisheries and Oceans, Canada.

Sketch of ice-profiling sonar mooring deployed on the bottom of the ocean. Design by Dr. Humfrey Melling of Fisheries and Oceans, Canada.

There are lots of challenges to deploy such a sensor system, there are more challenges to find and recover it in later years, and then there are the challenges to analyze and interpret the data writing the software that does it all. None of the many parameters such as speed of sound, ocean density, atmospheric pressure, and amount of water above the sensor are known very well, all of them change with time from day-to-day and sometimes even hour to hour. In order to measure ice thickness within a few inches (10 centimeters, say), we need good estimates of these things. I work with PhD student Patricia Ryan on this and we are almost done to untangle these many data strands for all of 3,300 days that we have observations in Nares Strait. Lets start with a random day exactly 10 years ago:

Ice draft below sea surface for May 30, 2004 in Nares Strait. Data shown are 15 second averages.

Ice draft below sea surface for May 30, 2004 in Nares Strait. Data shown are 15 second averages.

The bottom of the ice is about 1 meter (~ 3 feet) below the surface, but at about 6 pm (18:00) it becomes 0.2 meter thinner to return to its original thickness near midnight. A thicker piece of ice must have moved in and out of the “view” of our sensor. So far, so good, but you can already see that ideally I also would want to know the motion of the ice in addition to its thickness, but that is another story. Also, please recall that we got about 9 years of such data or about 3,300 plots, so, let me show you a second one, but this one is really bad:

Ice draft below sea surface for April 18, 2005 in Nares Strait.

Ice draft below sea surface for April 18, 2005 in Nares Strait.

The ice here is a little thicker, but not by much. What stands out are three funky looking, abrupt jumps every 6 hours precisely. How can this be? Well, it cannot and I must have done something bad to the data. Recall that we need speed of sound and water density estimates to convert acoustic travel time to ice draft. On April 18, 2005 my estimates perhaps were off. But why? And how can this be fixed?

The first clue is revealed in a month-long series of speed of sound that I estimated from a different mooring that measures temperature, salinity, and pressure along a string. Using some fancy math that a prior PhD student of mine developed (Dr. Berit Rabe), I estimate the vertical sound speed averaged from 100-m depth where the ice-profiling sensor is located to the surface where the ice is located. The plot below shows how this speed varies during the month of April 2005. It has some wild undulations near April-18:

Vertically averaged sound speed for the month of April 2005. Black curve is for 6-hourly and blue curve is for 24-hourly estimates.

Vertically averaged sound speed for the month of April 2005. Black curve is for 6-hourly and blue curve is for 24-hourly estimates.

For most of the month the speed of sound is about 1440 meters per second (m/s), but it spikes to almost 1446 m/s on April-18. It is this unrealistic spike that causes the estimated draft of the ice to go up and down by 20 to 30 centimeters.

The second clue and likely fix to my “ice offset problem” is the blue curve in the above plot. Using the same fancy math, I there come up with an estimate of the speed of sound only once a day rather than once every six hours. There are still fluctuations, but they are much smaller without a big spike. So, to conclude, I pushed my fancy math too far and it crashed the same way that a flashy muscle car driven too fast will crash as either the car or the driver cannot handle the road anymore. I here crashed the car as physicists are prone to do. Ideally we do it in a safe environment such as crunching numbers on a computer … as I did here.

Hansen, E., Gerland, S., Granskog, M., Pavlova, O., Renner, A., Haapala, J., Løyning, T., & Tschudi, M. (2013). Thinning of Arctic sea ice observed in Fram Strait: 1990-2011 Journal of Geophysical Research: Oceans, 118 (10), 5202-5221 DOI: 10.1002/jgrc.20393

Rabe, B., Johnson, H., Münchow, A., & Melling, H. (2012). Geostrophic ocean currents and freshwater fluxes across the Canadian polar shelf via Nares Strait Journal of Marine Research, 70 (4), 603-640 DOI: 10.1357/002224012805262725

Formation of Nares Strait Ice Bridges in 2014

Darkness and cold covers North Greenland, Ellesmere Island as well as Nares Strait, the waterway that connects these two inhospitable places. And despite the darkness of the polar night, I can see that three beautiful arches made of ice connect Greenland to Canada. It is possible to walk across water, if the water is frozen. Stuck to land, ice arches or ice bridges shut down ice motion while the ocean under the ice keeps moving. Lets have a peek at how this looked from space yesterday:

Ice arches of Nares Strait on January 26, 2014 from MODIS thermal imagery.

Ice arches of Nares Strait on January 26, 2014 from MODIS thermal imagery. Surface temperatures in degrees Celsius are all below zero despite the missing “-” sign stripped by Adobe Illustrator.

The colors above show the temperature that satellite sensors “see” at the surface of the ice. Red is warm, blue is cold, and grey is land, but “warm” here is still below the freezing point of sea water near -2 degrees Celsius, so even the red or “hot” spots are covered by ice. The 300 deep ocean in Nares Strait generally flows from north to south without trouble under the ice, but just behind the fixed arching ice bridges, it sweeps the newly formed thin ice away to the south. The “warm” spots that form to the south of each ice arches have their own stories:

Farthest to the north a massive ice arch spans almost 200 km (150 miles) across. It faces the open Arctic Ocean to the north and it formed a few days before Christmas 4-5 weeks ago. It was still shedding large ice floes from its edge as it tried, and finally succeeded, I think, to find a stable location. Nevertheless, one of its larger pieces of ice moved into Nares Strait on January-3, 2014 where it became stuck on both Greenland and Ellesmere Islands:

The large floe from the edge of the first ice arch becames firmly lodged on both sides of the 30-km wide entrance to Nares Strait on January-4 (not shown), perhaps aided by strong winds from the north with wind speeds exceeding 40 knots (20 m/s). This second northern arch then aided the formation of the third ice arch in the south. All three arches became first visible on January-8:

Jan.-8, 2014

Jan.-8, 2014

A subsequent lull and short reversal of the winds brought warm southern air masses into Nares Strait while water and drainage pipes froze at my home in Delaware:

Weather record from Hans Island at the center of Nares Strait for January 2014. [Data from Scottish Marine Institute in Oban, Scotland.

Weather record from Hans Island at the center of Nares Strait for January 2014. [Data from Scottish Marine Institute in Oban, Scotland.

“Warm” here refers to -10 degrees Centigrade (+14 Fahrenheit). Air temperatures in Nares Strait today are -21 degrees Celsius (-5 Fahrenheit) while ocean temperatures under sea ice are near -1.8 degrees Celsius (+29 Fahrenheit). It is these “hot” waters that “shine” through the thinner ice as the satellite senses the amount of heat that the ice surface radiates into space. More details on this one finds elsewhere.

I enjoy these elegantly arching ice bridges across Nares Strait, because they challenge me each year anew to question how sea ice, oceans, air, and land all interact to produce them. Nobody really knows. It is a hard problem to model mathematically and many graduate theses will be written on the subject. A student in our own program, Sigourney Stelma, just presented first results and movies of computer simulations of ice bridges forming. Perhaps I can convince her to post some of them on these pages?

Kozo, T.L. (1991). The hybrid polynya at the northern end of Nares Strait Geophys. Res. Let., 18 (11), 2059-2062 DOI: 10.1029/91GL02574

Kwok, R., Pedersen, L.T., Gudmandsen, P. and Peng, S.S. (2010). Large sea ice outflow into the Nares Strait in 2007 Geophys. Res. Let., 37 (L03502) DOI: 10.1029/2009GL041872

Muenchow, A. and H. Melling. (2008). Ocean current observations from Nares Strait to the west of Greenland: Interannual to tidal variability and forcing J. Mar. Res., 66 (6), 801-833 DOI: 10.1357/002224008788064612

Ruins of Fort Conger in the High Arctic

Retreating from Fort Conger, the U.S. Army lost 68% of its men to death by starvation and drowning. They were delivered to the northern shores of Ellesmere Island within sight of northern Greenland by the SS Proteus on August 12, 1881 and were left with ample food and fuel to survive and explore comfortably for a years or so. Continue reading

Petermann Ice Island Breaks while Plowing into the Bottom

The Manhattan-sized ice island that last year broke free of Petermann Gletscher in North Greenland plowed into the bottom and broke apart. Force equals mass times acceleration. When 18 giga tons (mass) of moving ice crashes into the ocean’s bottom 200 meters below the surface (acceleration), then something gotta give. And give it did, Continue reading