Tag Archives: oceanography

Of Moorings, Elephants, Norwegians, and Codswallop

The oceans are cruel, unforgiving, and destructive. Microbes, algae, plankton, fish, and whales all evolved slowly to make the seas their home. We men and women of science and technology race to catch-up with our steel, our sensors, our computers, our hope, and our wishful thinking. We place ourselves on powerful ships to lower fancy rigs into the water that poke the deep and icy Sea to reveal her secrets. We often wait a year or two or three to pick up our litter of machinery hoping that the sealed battery, electronics, and computer containers are still there with added data. There are thousands of small things that all must go just right to be successful, but one only needs one failure, one oversight, one faulty wire, one scratch or one hair on a rubbery seal, or one wrong letter in a deployment command code and the entire enterprise is doomed to fail. Sisyphus of the Greek tragedies come to mind as does Captain Ahab and his insane quest to control nature. We need time to evolve.

Less than 100 years ago Harald Sverdrup was the first to deploy a machine in the Arctic Ocean off Siberia to measure ocean currents. He used these data to write about tides, forces, and balances to make predictions on how wind and ice drive ocean currents and vice versa. This was many years before he transformed ocean-research to ocean-going research as director of Scripps Institution of Oceanography in San Diego, California during the Second World War. As a “Resident Alien” from Norway he helped the Americans win the war by organizing scientists into skilled ocean-going groups to better predict waves, weather, and acoustics. Revolutionary measurements and advances were made with minimal bureaucratic overhead and results were used immediately to land troops on African and European beaches, to send planes with bombs to raid on Germany and Japan, to equip destroyers with sonar to hunt and sink submarines. After the war Sverdrup returned to his home country to direct the Norwegian Polar Institute with a deep sense of duty to help rebuild a Norway devastated by war and occupation. The basic design of his current-measuring device still exists today, made by Aanderaa. This Norwegian company has a stellar reputation for simple yet robust design that transitioned into the computer age.

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It is very easy to deploy ocean moorings by slipping them gently into the water. In contrast, it is not so easy to get the sensor package back years later, because they have to respond to commands sent via remote control, a metal rod has to turn a motor to release a set of buoy and floats from iron anchors, the buoy has to raise everything to the surface, the sensors and the water-sealed computers driving them must be hauled onto the ship with ice, fog, or waves all complicating matters, and finally, there must be working connection to the data storage unit that must have operated correctly. Each step appears simple enough, but the long drawn-out sequence of many such steps, each critical, makes this such a risky and tricky business. Corrosion of metals in seawater, too, attacks any unprotected surface, hence many sacrificial pieces of metals are placed on any mooring with metal components. The pin to a shackle rusting away can endanger an entire mooring line. It boggles my mind that anything ever comes back, as often it does because of people like this one:

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Olaf S., Benjamin R., and Agnieszka B. successfully recovered two moorings yesterday that were placed in 2012 in water more than a mile deep. It speaks to their skill and that of the crew they are with both now and 2 years ago. It was a good day’s work without much time to sit down for meals, Olaf told me on deck where he was in the weather all day. Ben made the fateful decision the day before not to release the moorings for much fog and ice would have endangered the mooring once at the surface, but he was there the following day at 4:30 am to decide on the release that was successful. Those are hard calls to make. There are 9 more such moorings that need to come back and one that will require lots of additional attention: The day prior we had sailed through fog and ice all day only to find one mooring collapsed into a messy pile of rope, imploded buoys, metal, and sensors about 8000 feet (2600 meters) below the surface. The cause for this failure is not known, but speculation is, that a 30’’ steel float got crushed when an iceberg or some other failure depressed the float below its breaking point. It was a frustrating day, but a little less fog, a little less ice the following day, and Ben, Olaf, and Agnieszka led several successful recoveries yesterday. It was also the last day of our expedition.

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We still have a long way to go in our attempts to describe or understand the oceans to better predict how it impacts present and future climate. I compare this task to three blind men poking an elephant: One near the back notices a bushy tail that appears to correlate with a smelly source of gas, the second gets under a foot, describes a very hard woody surface that subsequently crushes him, while the third in front notices a rubbery pipe that wiggles like a snake. Their individual descriptions are costly, accurate, incomplete, and misleading. I often wonder, if our physical descriptions of the ocean do not have similar qualities, never mind more complex areas that involve living things such as elephants. Codswallop!

Posted by Pat Ryan for Andreas Muenchow

Deep Sea Biology and Chemistry: Muddy Business

Mud, mud, and more muddy mud was hauled from the bottom of the ocean for
the last five days from depths of one, two, and even three miles below the
icy surface. The biologists aboard are having a field day with mud and all
life forms that relate to mud. The mud is on their faces, mud is on their
pants, mud is on sampling dishes, there is mud in the air, mud in the
hair. People on this ship poke, grab, extract, label, profile, and film
mud. There are people filling vials with mud, people sucking water from
the mud, people running mud through fancy coffee filters, people preparing
mud with chemicals for later analyses.

The fascination with mud, mine included, makes me wonder if perhaps there
is something to the many creation stories that we all evolved out of the
mud. Perhaps what is done here and elsewhere is to decoding mud in search
of life and how life works deep down. The clean and un-muddied people are
shallow water physical oceanographers like myself who barely touch water,
never mind mud; but I got a beer cap of mud from 3 miles down sitting on
my computer as I type these lines.

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It was not always like this for me: I grew up a few miles behind the dikes
of Germany’s West Coast. No promising sunny California with its rocky
inter-tidal, but endless tidal mud-flats extending to the horizon on a low
tide. We had battles with mud as kids when the tide was out and were
hosed down a few hours later by the incoming tide. Water waist-deep, we
then dove into the ground, head-first to feel the gentle impact of the
soft mud half a foot thick. Fun, children playing with mud. It was fun
because it was both dirty and smelly business.

Strangely, though, the mud that many biologists aboard are excited about
does not smell … but let me double check by asking Ulrike B., if she lets
me smell some of her mud that she just captured with a massive contraption
that she had moored about a mile deep for 36 hours collecting mud in
containers and sampling it with fine glass electrodes to measure microbial
activity. Microbes are tiny critters neither plant nor animal, a little
like the bacteria that give you the sniffles, and they are everywhere
doing lots of funny chemistry in our stomachs, throats, as well as the
bottom of the ocean.

The mud aboard does not smell, not even a tiny bit. Ulrike B., who is from
Belgium and who knows the mud-flats of the North Sea well, just told me:
“I had to smell the mud at first, too, it is none of that stinky mud we
got in the North Sea.” Wondering why, I was told quickly, “… lots of
oxygen …” as she handled 3 samples sorting and preserving them. Ian S., a
British chemical oceanographer without an urgent task at hand explained in
more detail the difference between smelly estuarine and deep sea mud:
“Most of dead matter sinks from the surface to the deep sea where bacteria
help decompose it by uses dissolved oxygen in the water-column. Hence
there usually is enough oxygen in surface sediments for bacteria to deal
with the small amounts of organic matter that arrive.  In shallow waters
more organic matter arrives, at the bottom, bacteria use it up quickly and
then switch to other forms of oxygen that often releases sulphur
compounds, giving shallow sediments a strong smell.

There was also something about receptors that made me think of oxidation
potentials, but I had my answer, I felt.

Image

So, in summary, the North Sea mud smells, because there is so much life in
it. And as this life dies, it starts a new cycle that uses up the oxygen
in the mud. The fancy word for life is “organic matter” as it refers to
plants and animals. These plants and animals also fix carbon, the stuff
that we burn in our cars that makes our globe a little warmer each year on
average. When these carbon-based life forms die and sink to bottom of the
ocean, they decay almost the same way on the bottom of the ocean as a
banana peel is rotting away on my compost pile at home.

The process of “rotting” uses up oxygen. There is plenty in the air, but
not always on the ocean floor, except the deep ocean, few rotten bananas
here. Microbes probably help to eat up the dead stuff using oxygen and
making nutrients that then becomes food stuff for living things. Better
have a biologist proof-read this, as this stuff is not my cup of tea.
Physics and mathematics are so much easier to deal with than this fuzzy
thing called life and its many competing and co-operating cycles

Posted by Pat Ryan for Andreas Muenchow

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

North Greenland Glacier Ice-Ocean Interactions 2014

I will travel to Spitsbergen in six weeks to board the German research icebreaker Polarstern. She will sail west across the Fram Strait towards northern Greenland where some of the last remaining glaciers exist that still discharge their ice via extensive floating ice-shelves. If all goes well, we will deploy instruments on the bottom of the ocean across a 30 km wide submarine canyon (Norske Ore Trough). The instruments profile ocean velocities from the bottom to the surface of the canyon that connects the deep (warm) ocean to the shallow continental shelf areas which then connect to two large outlet glaciers, Zachariae and 79N Glaciers. These are two of three glacier that terminate the North-East Greenland Ice Stream (NEGIS) which contains about 15 per cent of Greenland’s ice sheet:

Speed of Greenland's ice sheet movements. NE indicates the fast-moving (red) North-East Greenland Ice Stream with 3 branches connecting it to the ocean. [From Mauri Pelto's blog]

Speed of Greenland’s ice sheet movements. NE indicates the fast moving (red) North-East Greenland Ice Stream with 3 branches connecting it to the ocean. [From Mauri Pelto's blog]

The most southern is Storstrommen Glacier, a tidewater glacier with an almost vertical glacial front attached to the bedrock. The next one up north is Zachariae Glacier which lost its extensive ice-shelf during the last 3 years in a dramatic collapse reported on Mari Pelto’s blog. Presumably, there is little floating ice-shelf left that is attached to the lacier. And only 30 km to the north, we have 79N Glacier whose real name is the Danish Nioghalvfjerdsfjorden. It rivals Petermann Gletscher in ice discharge, areal coverage, thickness, and more with one exception: Nioghalvfjerdsfjorden’s ice-shelf appears remarkabe stable, nobody knows why exactly, but it may provide clues on how Greenland’s ice sheet interacts with and responds to forcing by the oceans. I show a recent Landsat image taken from Neven’s Arctic Sea Ice Forum; the floating glacier is on the left (east) of the image with a set of 5-7 out-cropping islands towards the right (west) providing some pinning support for the ~30 km wide front of the glacier:

Landsat image of Nioghalvfjerdsfjorden on Mar.-22, 2014.

Landsat image of Nioghalvfjerdsfjorden on Mar.-22, 2014.

Our 2014 study area is actually to the east, just outside the frame of the above image. The reason is lack of ship time, as this year’s deployment is just a small pilot study to better prepare and understand a larger German-led experiment that will take place both on the glacier and its adjacent ocean and land in 2016 and, I hope, beyond. Furthermore, we are scheduled to be there in June, a tad early for all the sea ice to clear out of the area (79N Glacier MODIS summer imagery) which also explains my intense interest in how the ice develops. And a first fairly clear MODIS image came about yesterday morning:

Ice-covered coastal waters off northeast Greenland April 14, 2014. Red contour indicates 100-m water depth. The "horseshoe" shaped red island is Belgica Bank with Norske Oer Trough to its south-west.

Ice-covered coastal waters off northeast Greenland April 14, 2014. Red contour indicates 100-m water depth. The “horseshoe-shaped red island is Belgica Bank with Norske Oer Trough to its south-west.

Belgica Bank is about as big as the Georges Bank in the Gulf of Maine. In past decades rafted multi-year ice and tabular icebergs often grounded over shallow Belgica Bank and thus provided an anchor to maintain stability for a year-round land-fast ice cover called the Norske Oer Ice Barrier. This year-round land-fast ice area, however, disintegrated in 2003 and has become an intermittent and not a regular feature for unknown reasons.

Before I can get onto the German icebreaker in Spitsbergen, my 3500 kg of equipment had to be repaired, rebuilt, re-powered, and shipped from British Columbia to Germany via rail, ocean freighter, and truck. It all arrived in 86 pieces only last friday, two weeks behind schedule, because of ice and confused shipping schedules in the Canadian Gulf of St. Lawrence. Lots of great people in Canada, the USA, and Germany made it happen. Wish us luck for the next step in this exciting scientific exploration to reveal one of many of Greenland’s glacier and ocean mysteries.

Hughes, N., Wilkinson, J., & Wadhams, P. (2011). Multi-satellite sensor analysis of fast-ice development in the Norske Øer Ice Barrier, northeast Greenland Annals of Glaciology, 52 (57), 151-160 DOI: 10.3189/172756411795931633

Wadhams, P., Wilkinson, J., & McPhail, S. (2006). A new view of the underside of Arctic sea ice Geophysical Research Letters, 33 (4) DOI: 10.1029/2005GL025131