My last contribution on this blog reminded the importance of in-situ data measurements on the evaluation of numerical modeling used to predict climate. As part of my PhD thesis, I had the chance to record, process and analyze observations across and along the Reykjanes Ridge within the framework of the RREX project. It included an experience at sea during the RREX cruise in 2017, which was an amazing human and scientific experience. Now that my PhD ended, I would like to tell you about the scientific results that were obtained.
During my PhD, I studied the connection between the Iceland Basin and the Irminger Sea through the Reykjanes Ridge. A main result was to describe and quantify the top-to-bottom transport of the subpolar gyre that crossed the Reykjanes Ridge during the summer 2015. These results highlighted interconnection between the two main along-ridge currents: the southwestward East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the northeastward Irminger Current (IC) in the Irminger Sea. From about 56 to 63°N, the hydrological properties, structures and transports of the ERRC and IC consistently evolved as they flowed along the Reykjanes Ridge. During my PhD, I showed that these latitudinal evolutions were due to flows connecting the ERRC and IC at specific locations through the complex bathymetry of the ridge, but also to significant connections between these currents and the interiors of the basins. These results highlighted a more complex circulation in the vicinity of the Reykjanes Ridge than it was assumed.
From three different cruises and Argo floats, I also investigated the deep circulation and properties of overflow water through the deepest sills of the Bight Fracture Zone. At the end of my PhD, I showed the strong variability of its transport and property over time by comparing three successive years. Now, I think that it could be interesting to continue this study and to better understand the variability of overflow water at higher frequency. As a continuity of my PhD, I am thus exciting to investigate the variability and linkage between the overflow water transports and properties across the Iceland-Scotland Ridge and the Denmark Strait as part of my postdoctoral position. These inflows from the Nordic Seas feed the lower limb of the Meridional Overturning Circulation and are crucial to characterize the variability of the North-Atlantic subpolar gyre. I am excited to fulfil this study by using the OSNAP array that provides new and key measurements of the AMOC, and also to move in USA for a new beautiful and rewarding postdoctoral experience.
The end of the year is a time to reflect on the past and make long-term plans for our future. Some readers of this blog, especially our young audience, may be considering a career in oceanography or climate science. I will tell you my story: what motivated me to join this field and the factors that shaped my career path.
My first encounter with physical oceanography was 14 years ago, at an international summer school where I learned basic gravity wave dynamics. Fluid motion fascinated me and sparked a lasting interest in the field. The following year I was on my high school team for the International Young Physicists’ Tournament (IYPT). Within our team, I was responsible for problems related to fluid dynamics.
By the time I began my undergrad studies, I was already very interested in modeling the environment. I also realized that to do well in the natural sciences, I should expand my background in math. So I majored in Applied Mathematics, but I also took physics courses. As an undergrad, I did different research projects applying mathematical methods to study the environment. For example, my senior thesis was on modeling the El Niño / La Niña phenomenon.
Nine years ago, I decided to do a Ph.D. in climatology and oceanography. I became interested in the field because I wanted to do research in an area of science that is socially significant. Nature has direct impact on humankind. At the same time, climate science and oceanography attracted me because many fundamental questions in our field remain unresolved.
My Ph.D. and postdoc research has explored the large-scale ocean circulation and its impact on global and regional climate. I have studied various parts of the World Ocean: the North Atlantic, the Arctic Ocean, and the Southern Ocean. My work involves coding algorithms and analyzing data from complex climate models and observations, but also developing simple conceptual models.
In my current OSNAP project, I examine how the ocean circulation in the subpolar North Atlantic responds to local and remote fluctuations in atmospheric conditions. I analyze the computer code of a global ocean model as if it were a system of math equations. One of the most interesting aspects of my work is trying to understand the ocean’s delayed response to past atmospheric changes that took place years ago.
I am now looking forward to another productive year of research on the ocean circulation. Happy holidays to all readers of this blog and best wishes for the New Year!
The sea and the ocean have always held a fascination for me. I grew up in the bay of Saint-Malo (France) and the sea coast was my first playground (Figure 1). During my childhood, I was mostly interested in the processes involved in sandcastle destruction by waves, or in the tide processes that could not be ignored for safe crab fishing. When I was a little older (and braver), I started exploring the sea and left the beach and the rocks behind me. Sailing, surfing, windsurfing and kayaking became my favourite hobbies. Boat rides were always fun and exciting. Visiting traditional sailboats or big fishing vessels were captivating and it nourished my imagination and my dreams of sea adventures. I used to think: “One day, I will also be on a boat to explore the ocean and learn more about it!”.
Figure 1: My playground back home (Grande Plage de Saint-Lunaire, France). Photo by: Charlène Feucher.
I would later discover oceanographic sciences: the ocean was not only my playground anymore, it could now be my field work too! I was very glad to start a master in physical oceanography at the University of Brest (France) and learn the secrets of the ocean (with an affinity for the Atlantic Ocean), how it works, and why its role is of paramount importance to the global climate.
During my master studies, I got the opportunity to complete two projects that introduced me to physical oceanography research. My first internship was at IFREMER and IUEM (Brest, France) to evaluate realistic hydrodynamic simulations for biogeochemical applications. I developed inter- comparisons of several ocean simulations (differing in resolution and model parameters) and evaluated the simulated fields against relevant observation data sets, with a focus on mixed layer dynamics in the North Atlantic Ocean. I did a second internship at Woods Hole Oceanographic Institute. The project was to study the dissipation of the North Atlantic Subtropical Mode Water (also well known as Eighteen Degree Water) based on eddy-resolving ocean simulations. I examined the eddy covariance flux divergence of the North Atlantic Subtropical Mode Water thickness and potential vorticity to understand the spatial distribution and mechanisms of the destruction.
After my master thesis, I came back to the University of Brest to complete my PhD. The objective of my PhD project was to evaluate the properties and variability of the stratification in the North Atlantic subtropical gyre. I developed a method to characterize the properties of the stratification of the ocean (permanent pycnocline and mode waters) in subtropical gyres. Focusing on the North Atlantic subtropical gyre and based on the use of Argo data. I have documented the properties of subtropical mode waters and permanent pycnoclines.
Right after PhD, I travelled to Canada to start a postdoc at the University of Alberta (Edmonton) where I am still working. My postdoc research focuses on the relationship between the meridional overturning circulation and the formation of the Labrador Sea Water. This study is based on the use of NEMO model outputs with an Arctic and Northern Hemisphere Atlantic configuration.
In Edmonton, I am living far from the ocean but I never forget about it. The sea is always calling me and when cruise opportunities are out, I am willing to embark when possible. My first experience at sea was in 2015 during my PhD. We took several measurements along and across the Reykjanes Ridge to study the ocean circulation there. This first research cruise was full of discoveries. I learnt what oceanographic field is all about, how to take measurements, and how life aboard a ship feels like. I was enchanted by the immensity of the ocean and the power of the winds and waves during strong storms (small storms according to the Captain but I was not convinced).
I got the chance to renew this sea experience in June 2018 on board of the RV Maria S. Marian. This cruise was quite epic! We flew to Cadix (Spain) where the boat departed. We crossed the whole Atlantic while taking measurements, we docked in St. John’s (Canada) for a day and then we crossed the whole Labrador Sea before coming back to St. John’s where our cruise ended. Seven intense weeks at sea! During this cruise, I was amazed to see icebergs for the first time, admiring them drifting off the Greenland coast under a beautiful sunset (Figure 2). Performing CTD casts with the Greenland coast in the horizon was also a very special moment (Figure 3). And more importantly, I was glad to take measurements in the Labrador Sea to observe deep convection and compared these observed results with what we simulated in our NEMO model.
Figure 2: Sunset and iceberg, from the RV Maria S. Merian in June 2018. Photo by: Charlène Feucher.
Figure 3: CTD cast near Greenland coast, from the RV Maria S. Merian in June 2018. Photo by: Charlène Feucher.
Physical oceanography research work gives me the opportunity to work in different places and and meet many great people. This is full of very enriching experiences, professionally but also personally. I hope I can continue this oceanographic adventure in the years to come.
As this is the last blog post of 2018, it is time to leave you wishing everyone a wonderful Christmas season from a freezing cold and white Edmonton!
Now that temperatures outside are dropping and storms are raging over the subpolar gyre, it is clear that the OSNAP field season had ended. Many blogposts have been written about the exciting adventures at sea last summer. This time however, I would like to tell you a bit about the – slightly more boring – work that happens after. When the exhausted but ultimately satisfied scientist returns home, with a hard drive full of newly recovered data; that’s when our real work begins. Before the new data can be used to answer actual science questions, they are in dire need of some cleaning.
Why is that necessary? Instruments on a mooring (a cable anchored to the sea floor) are impacted by currents, storms, tides and sometimes fishing activities. There is the risk of colonization by omnipresent sea creatures. In the vast open space of the ocean, an instrument can provide a welcome place for shelter. Instruments deployed in the sunlit surface layer are all overgrown with algae upon recovery. But deeper instruments can also host interesting inhabitants, such as the anemone in the picture below. Last but not least, the ocean is salty, wet and under high pressure. A challenging environment for an electronic instrument, especially with our long deployment period of two years!
Figure 1: Some examples of sea life on the moorings upon recovery: a slimy creature on a Microcat, an anemone growing on a ring of the release that was at almost 2000m depth, and a shallow UK buoy overgrown with algae.
Data quality sometimes suffers from all these environmental impacts. This is where my work of the past few weeks comes in: checking, cleaning and processing the raw data records. Below are examples of Microcats on one of our moorings, called IC2, during the last deployment. Unlucky for us, the anchor of this mooring ended up shallower than planned, on top of a small seamount. A storm resulted in the exposed top buoys breaking down, making the shallow instruments sink to the deep. The top Microcat, originally at 25m, was instead dangling loose at around 700m depth… it is a small miracle it was still attached to the cable when the mooring was recovered!
(For those who are wandering; yes, luckily there was another buoy at 350m, keeping the deeper part of the cable standing up straight!)
Severe storms impact the mooring even deep down in the water column. The pressure record of the Microcat at 352m depth (figure 2) still shows many big and small ‘blowdown’ events. During such an event, strong currents push against the mooring cable, blowing it down at an angle and pushing the instruments deeper into the water. When the storm ceases, the buoys on the cable pull the mooring cable back to its original straight position.
Figure 2: Pressure time series of the Microcat at 352m in mooring IC2 for the last deployment (August 2016 to July 2018)
Microcats also measure temperature and salinity. Figure 3 shows the raw salinity record from the deepest Microcat on IC2, close to the bottom at almost 1900m depth. As you can see, salinity differences in the deep ocean are generally very small. However, salinity measurements are notoriously noisy, so we need to perform some filtering of data spikes. But which spikes are bad data, and which represent real variability? Then there is a suspicious drop at the start of the record; perhaps a small animal or algae was temporarily covering the sensor?
Figure 3: Raw salinity record from the deepest Microcat in IC2, at 1892m
Lastly, and perhaps most importantly, we need to perform a calibration for all sensors. From the ship, we dip the instrument into the ocean and test its readings against a calibrated reference sensor to determine any offsets, both before and after the deployment. This is the only way to check whether an instrument gives accurate readings.
Overall, it is probably clear that there is a lot of effort involved in scrutinizing the records and ensuring data quality control is performed correctly. But although it may sound a bit tedious, the quality control step is extremely important. It ensures that we have accurate, reliable records, on which we can build for further analysis – to eventually formulate valid answers to scientific questions!
No, not an OSNAP cruise this time, but in the balmy subtropics at 26°N.
I am leading a group from the University of Miami and NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) on this 18 day cruise, where we will recover and replace several deep moorings and collect hydrographic profiles near the ocean’s western boundary off the Bahamas as part of the RAPID/MOCHA program (http://www.rapid.ac.uk/rapidmoc/). One of our key goals is to monitor the strength of the Deep Western Boundary Current (DWBC) that carries deep waters formed in the subpolar region southward toward the equator, in the lower branch of the Atlantic Merdional Overturning Circulation.
Unlike our OSNAP cruises, we are wearing t-shirts on deck and scanning for the elusive “green flash” on clear days at sunset – a somewhat more comfortable existence to be sure, but as on all cruises the work is nonstop. We’ve experienced a short November gale on this cruise that shut down our sampling for awhile, but we are mindful of the fact that we’d much rather be here now than up in the high North Atlantic!
The last CTD recovery before shutting down our overboarding operations.
Even though the subpolar gyre seems far, far away, the data we are collecting on this cruise is a constant reminder of the connection between what is happening here in the subtropics and in the subpolar region. We can see clear evidence in the DWBC water mass properties of changes in the intensity of deep water mass formation in the North Atlantic over the past few decades. Although the RAPID program only started in 2004, the AOML group has been making measurements of the water mass composition of the DWBC here since the mid-80’s as part of their Western Boundary Time Series (WBTS) program. The biggest change occurred in 1995 when a new pulse of much colder and fresher (less salty) water originating from the Labrador Sea arrived at 26°N. This pulse followed a period of very strong cooling in the Labrador Sea starting about 9 years earlier that resulted in the deepest and densest formation of Labrador Sea Water in more than 60 years. The 9-year transit time for that pulse to arrive off the Bahamas means it couldn’t have all come in a fast-track pathway within the DWBC itself, but very likely followed one or more pathways through the ocean interior, for which there is other independent evidence. The peak of that event occurred in about 2003 off the
Bahamas, again just about 9 years after the peak of deep convection in the Labrador Sea in 1994. Since that time the waters in the DWBC off Abaco have gradually warmed, while deep convection in the Labrador Sea has generally decreased.
All that changed in 2014 with the onset of very strong cooling again across the subpolar gyre and extensive deep convection in the Labrador Sea – coincidentally (but auspiciously) timed with the start of OSNAP. If this turns out to be a sustained multi-year event, which it seems to have the makings of, then the next several years will be very interesting. Will this be a playback of the mid-90’s event, or will something different happen? We know the ocean is taking up a great deal of the excess carbon dioxide we are putting into the atmosphere, and that the deep water mass formation in the North Atlantic is a key element of that uptake. What we know much less about are the pathways and processes by which carbon is transported and stored in the ocean and he time scales of those deep ocean transport processes. Obviously we’ll have to wait a while to find out what happens, but the difference this time around is that we will have the OSNAP, RAPID, and other deployed AMOC arrays, as well as the fully-deployed Argo array, to help us out. THAT is progress.
On 8 October a special report was released from the Intergovernmental Panel for Climate Change to highlight the impacts of global warming of 1.5oC above pre-industrial levels. The report is substantive and is led by 91 authors drawing upon inputs of over 2000 experts, nearly 500 reviewers and citing 6000 papers. The report is set in the context of the Paris Climate agreement in 2016, which aspires to keep global temperature rise to less than 2oC this century and to pursue efforts to limit the temperature rise even further to 1.5oC. What has been unclear is how long have we got until we reach this warmer climate and what are the likely consequences?
The headline is alarming, the clock is ticking faster than we would like. There are a dozen years to keep below a global temperature rise of 1.5oC. We are on track to exceed this threshold by year 2030 given the present rate of carbon emissions. The message is simple: the more carbon we emit, the warmer the climate system becomes. We need to reduce the amount of carbon we are emitting to the atmosphere.°°
The report assesses how a 1.5oC warmer world compares with a 2oC warmer world. Drawing upon climate model projections, there are robust differences in regional climate between a 1.5oC and 2oC warmer world: the mean temperature and extreme temperatures are higher for a 2oC world (high confidence) and there is heavier precipitation in some regions and drought in some other regions (medium confidence), and that there is an extra 10cm of sea level rise, affecting 10 million more people. The effects on the habitat are viewed as alarming with twice as much habitat loss for plants and insects for 2oC warming compared with 1.5oC warming. Warm-water corals are effectively wiped out with a 99% loss for 2oC warming, while 10% might survive with 1.5oC warming. Arctic sea-ice free summers are viewed as being once every 10 years with 2oC warming, rather than once every 100 years with 1.5oC warming.
There are real benefits to acting sooner to limit the increased warming of the climate system. What is needed is to reduce the amount of carbon emissions and the resulting amount of carbon dioxide in the atmosphere. Proposed solutions include reforestation, a shift to electric transport systems and development of carbon capture. The challenge is severe, we need to reduce global carbon emissions by 45% from year 2010 to 2030. We can only achieve this goal by keeping as much carbon as possible in the ground and not releasing further fossil fuels. Meeting this challenge will be demanding.
PDRA positions in Physical Oceanography Oban, Scotland
Fixed term appointment for 3 years
£27,285-£30,688per annum
The pre-eminent scientific challenge of the 21st Century is to understand the drivers of Earth’s climate. The North Atlantic subpolar ocean is closely coupled to Arctic, European and tropical regions through the atmosphere, and is strongly linked to decadal climate variability. At SAMS we are researching the physical processes of ocean-atmosphere interaction and circulation.
Position 1
SAMS has a leading role in developing sustained observing programmes in the subpolar Atlantic for example through joint leadership of the International Overturning in the Subpolar North Atlantic Programme(http://www.ukosnap.org/ & http://www.o-snap.org/).OSNAP is a world leading subpolar transatlanticmooring arraypurposefully designed to elucidate links between Atlantic circulation and climate. You will be responsible for taking a leading role in analyzing observations from the NERC funded OSNAP programme.
We seek a Post Doctoral Research Associateto manage and develop SAMS expertise in basin scale ocean observations for climate and to become a future leader in the field. The main duties are:
Contribute tothe preparation, planning and execution of CLASS research cruises and glider programme.
Contribute to the deliveryof objectives in EU programmes.
Lead and publish high quality peer-reviewed research.
Form and maintain national and international relationships and collaborations.
Travel to national and international meetings to present research findings.
Position 2
SAMS has a leading role in developing sustained observing programmes in the subpolar Atlantic for example through joint leadership of the recently funded £25M UK NERC Climate Linked Atlantic Sector Science Programme. This position will contribute to making new observations (moorings and gliders) and research on the topic of Ocean Salinity and the Hydrological Cycle. You will also contribute to two EU H2020 programmes Blue Action (focused on lower latitude drivers of Arctic weather and climate) and ATLAS (understanding physical controls on Atlantic cold water coral ecosystems).
We seek a Post Doctoral Research Associate to manage and develop SAMS expertise in basin scale ocean observations for climate and to become a future leader in the field.
The main duties of the position are:
Contribute to the planning and execution of glider based field programmes.
Lead and publish high quality peer-reviewed research.
Form and maintain national and international relationships and collaborations.
Travel to national and international meetings to present research findings.
When you decide to study the currents that whip past the continent of Greenland and that transform the waters in the Irminger and Labrador Seas, an oceanographer must be willing to make peace with an ocean that isn’t entirely liquid. The extreme elements that shape the rocks along the Greenland coast also actively chisel away at the hundreds of glacial termini that meet the ocean edge. This chiseling leads to a constant flux of icebergs, small icebergs called bergy bits, and even smaller ice chunks called growlers. With ice in its various sizes and jagged shapes breaking away from the entire continent, the currents in the OSNAP region transport and mix more than just water.
Logistically, the OSNAP study region is one of the hardest places in the world ocean to successfully execute fieldwork. To start, the East Greenland Coastal Current, the East Greenland Current, and the Irminger Current can flow at speeds well over 1 knot as they round the tip of Greenland. In addition to strong currents, the area is home to a record: the windiest place in the world ocean. Simple ship maneuvering tasks, such as holding station while collecting data or recovering moorings (Figure 1), become challenging for the mates on the bridge as unforgiving winds build up rough seas that are already swiftly flowing. Floating ice is quite literally the icing on the OSNAP cake.
Ice adds a whole new dimension, and phase of matter, to navigation and operations at sea. From a distance, it can be nearly impossible to decipher ice chunks from whitecaps and sea spray. Large icebergs can be easy to see if they express above the surface of the ocean, but the majority of an iceberg’s mass lies below the sea surface and is difficult to see. Ice can also block access to nearby fjords used for shelter in severe weather. These navigation dangers keep the R/V Armstrong mates on high alert at all times as they steer through storms, darkness, and thick fog.
In order to help navigation efforts, WHOI researchers employed the help of the Danish Meteorological Institute (DMI), which specializes in satellite sea ice imagery. DMI is able to provide the ship with updates on the location of ice based on satellites that take Infrared (to see through clouds) and visible images of the Earth’s surface. Not only is this information extremely helpful, the maps can be stunning. Ice information from our current OSNAP cruise (on September 9th) is shown in Figure 2. This satellite image from the southern tip of Greenland is an example of how satellite-detectible ice features disperse from their mother fjords into the surrounding ocean.
Ice can also run into the OSNAP moorings, pushing instruments out of the way, or even snapping them off their lines making it impossible to recover them and their precious data. Our six shallow moorings on the continental shelf were, in fact, designed with drifting ice in mind. Equipped with a tripod-like structure at their base, these moorings have most of their instrumentation mounted near the sea floor. In an attempt to capture shallow data, the moorings also have special tethers extending up from the tripod base with weak links to top flotation. These weak links are designed to break easily should an iceberg snag the line, with the break point located strategically below the flotation and above an instrument. In the event of tether breakage, the instrument sinks to the bottom, but remains attached to the rest of the mooring so that it can still be recovered. Figure 3 shows a depiction of this breaking process. Of the recovered moorings from this year’s cruise, three of the six shallow moorings had their top floats ripped off within less than a year!
With all of the challenges handed to us from ocean elements, our crew has excelled in accepting the challenges brought on by ice. Of all 16 moorings that we aimed to recover on this cruise, all have successfully come back. In the face of extreme weather and rough seas, we have completed over 240 profile measurements of ocean temperature, salinity, and velocity thus far. And through all of these challenges, no one can deny how much they still enjoy seeing the Greenland coast in full panache with its towering and craggy icebergs.
Figure 1. An iceberg off the stern of R/V Armstrong during a tripod mooring recovery during the current OSNAP cruise.
Figure 2. Denoted infrared satellite imagery courtesy of the Danish Meteorological Institute. Pink triangle indicate the position of satellite-identified icebergs throughout the southern Greenland region.
Figure 3. Illustration of the OSNAP tripod moorings with weak links to top flotation. The left mooring demonstrates a normal deployment, while the right mooring shows a deployment with interference from an iceberg. In the event of an iceberg snagging the upper mooring tether, the top floats are released and the shallowest instrument falls, while still remaining connected to the mooring.
Two weeks ago we left Reykjavik on the R/V Neil Armstrong for the last OSNAP cruise of the season, a five week expedition to the outskirts of Greenland. Our goal: “turn around” two sets of OSNAP moorings and taking as many CTD casts as possible. In fact, Chief Scientist Bob Pickart is well known for taking particularly large numbers of tightly spaced CTDs.
Every group will say this, but I think our region is the most interesting of the OSNAP array. East of Greenland, cold and fresh water from the north meet warm and salty waters that originate in the Gulf Stream. This place is a turning point for the ocean’s global overturning circulation, which helps stabilize the earth’s climate, yet measurements here are severely lacking, partly due to the conditions I will describe here.
You may already know all this, but I’ll start by getting you up to speed on oceanographer-speak just in case. Moorings are long wires dotted with instruments that are anchored to the sea floor and take measurements for as long as several years. We are picking up our moorings after a two year deployment and are only able to access the data in the instruments once they are on board. We are also deploying a new set of moorings to leave in the ocean for another two years. The moorings we are servicing range from 100m on the shelf to almost 3km long offshore!
The CTD (conductivity, temperature, depth) rosette is the workhorse of oceanography. This instrumentation package measures temperature, salinity and pressure/depth as it is lowered through the water column by a winch on the ship. It also includes Niskin bottles that are closed at various depths to collect water that is used for calibration and ADCPs (Acoustic Doppler Current Profilers) that measure ocean velocity. Our CTD package also includes a set of chipods, which Jonathan Nash from OSU very generously loaned me for this cruise. Chipods measure temperature gradients at high speed (100 measurements per second), providing a quantification of turbulent processes over centimeter scales. As our CTD sections survey ocean properties at finer spatial resolution than the moorings, we use these to learn about detailed ocean dynamics and to ground-truth the mooring measurements.
Our first priority on this cruise is to retrieve and re-deploy the OSNAP moorings. However, this can only be done in daylight and when it is calm enough to be lifting large objects in and out of the ocean. A group of mooring specialists from WHOI and the Armstrong’s deck crew physically deploy and retrieve the moorings while others (like myself) take notes. To take full advantage of being out here, anytime that we can’t do moorings, we are doing CTDs. And by we, I mean a small army of graduate students, postdocs and technicians who take 8 hour shifts round-the-clock to operate the CTD. Of course, none of this work is possible without the ship’s crew who get us where we need to go and keep us safe on our floating home for these 5 weeks.
I thought I knew what to expect, having been to sea several times before and having spent the better part of the last year analyzing mooring data from the first deployment. I was also fully aware that we were heading into stormy seas pretty late in the “calm season”. After all, we think the currents we are studying are driven by the winds that zip along the coast of Greenland and flare up at its ominously named southern tip: Cape Farewell.
During the first few days that reality set in as we rocked and rolled our way to our study site. For me at least, there is a difference between knowing its a stormy region and being tossed around in my bunk for 24 hours. Our chairs slid across the main lab as we gathered to discuss plans and even the most seaworthy in the crew held on tight as they staggered down the hallway. It didn’t always feel great, but it sure helped me internalize that this really is one of the windiest places on earth.
Once on the continental shelf of Greenland, we were greeted by stunning views and large craggy icebergs that were well worth the weather. During the first OSNAP deployment (2014-2016), the inshore-most mooring, CF1, was hit by such an iceberg and the instruments sitting at 50m and 100m fell to the seafloor about a year after deployment. While marveling at their beauty and size, I wondered how such iceberg casualties were not more common. Luckily, we managed to recover CF1 this time as well, though yet again the 50m instrument was knocked down to 80m less than a year into the deployment.
For the rest of our stay east of Greenland we alternated between mooring recoveries and deployments, doing CTDs through the night, and hiding behind the cliffs of Greenland when the weather turned. Our mooring operations were successful with the exception of one mooring on the shelf that has refused to surface thus far. We will be back for it as soon as we are done with the rest of the moorings, but it stands as a painful reminder that what we are doing here is difficult, and that the ocean is full of uncertainty and surprises.
Two days ago we crossed through the beautiful Prince Christian Sound to start all over again west of Greenland. Armed with successful mooring operations east of Greenland, two sections of CTDs and two weeks of experience working as a team, I think we are ready to take on the Labrador Sea!
Recovering the flotation sphere for mooring CF4 with an iceberg in the background. Pictured from left to right: Andrew Davies, Pete Liarikos, John Kemp and Brian Hogue.Photo by Isabela Alexander-Astiz Le Bras
The last step of mooring deployment is dropping this anchor off the fantail to the seafloor.Photo by Isabela Alexander-Astiz Le Bras
View of a glacier flowing into the Prince Christian Sound.
Its the 2018 OSNAP field season and we are aboard the R/V Neil Armstrong, the new pride and joy of Woods Hole Oceanographic’s fleet. Pictured below is the R/V Armstrong coming into dock in the old harbor of Reykjavik, Iceland after completing two days of loading in the “new” harbor down the quay. This is my first time on the R/V Armstrong and I have been looking forward to sailing on her ever since she came out of the shipyard.
The R/V Neil Armstrong coming into dock in Reykjavik, Icleand.
The cruise has gotten off to a good start and we are now about halfway through our month-long voyage. We have three science groups aboard, from the U.K. (the Scottish Association for Marine Sciences and the National Oceanography Centre, led by Dr. Stuart Cunningham), from Holland (the Royal Netherlands Institute for Sea Research, led by Dr. Femke de Jong), and from the U.S. (the Rosenstiel School of Marine and Atmospheric Science, University of Miami, led by myself). We have a lot to accomplish on this cruise, and it still boggles my mind how many mooring operations we are planning to do on this one cruise. Altogether we have 21 moorings to recover and 19 to deploy, most of which are mooring “servicing” operations, meaning that we recover and redeploy a replacement mooring at the same site, usually on the same day. The deck is full to the bulkheads with mooring gear, and many of the crew have commented that they have never seen the deck so full. Thanks to the ingenuity of the deck crew and mooring teams we managed to find a place for everything (whereupon I can now admit that I was secretly worried whether we would actually fit everything onboard!).
The array of moorings to be serviced on the OSNAP East 2018 cruise.
In addition to the mooring operations, we plan to complete a full line of CTD stations across the entire array, amounting to some 80 stations in total. At these stations we will be measuring full depth profiles of currents, water properties (temperature, salinity, and dissolved oxygen), and also drawing water samples for chemical analysis including dissolved inorganic carbon, nutrients, and nitrogen and silica isotopes.
Whew!
So far we have had very reasonable working weather, except for having to dodge the remnants of tropical storm Chris which came barreling through our array right where we happened to be working at the time. So, we picked up and ran to the far western end of our line to resume work there, forcing us to develop a new “Plan B” that reorganized the entire layout of the cruise.
Such is life at the mercy of the sea.
I find it ironic that during the four OSNAP cruises I have been on since we started the program in 2014, the worst storms we have had to deal with have all come up from the tropics as post-tropical storm events. So much for my plan of escaping from the summer storm season in Miami.
The last 5-day forecast for post-tropical cyclone Chris posted by the National Hurricane Center. The storm position on Saturday July 14th was right where we planned to be working at the time. Needless to say we decided not to stay around to see if the forecast track was correct.
One of the truly remarkable things about these OSNAP cruises – and in particular the part of the subpolar North Atlantic that we are crossing during this cruise – is that you can feel in your skin and bones just what effect the ocean circulation is having on the climate. Part of our cruise takes place on the “warm” side of the subpolar gyre, where the North Atlantic Current brings warm waters originating from the Gulf Stream to Rockall Trough off the coast of Scotland and to the eastern side of the Iceland Basin. This is the most looked forward to part of the cruise, where ocean temperatures are as high as 14 degC and surface air temperatures rise to match it. A look out the back door to the deck often finds people who are off watch milling about aimlessly, squinting in the warm sunlight and enjoying the beauty of the sea. Then, eventually, whether we like it or not, its time to cross westward into the western Iceland Basin and Irminger Sea, where air and water temperatures are more like 6-8 degC. And fog is almost everywhere. Suddenly you don’t see anyone on deck anymore unless they have to be.
The graph below shows the longitude along our track and the corresponding surface air and water temperatures. We started in the central Iceland Basin near 25 degE and first worked our way over to the coast of Scotland (~July 8th) and then headed back across the Iceland Basin and into the Irminger Sea where we are now. Just remarkable how similar these three curves are.
We have an outstanding group of scientists on this trip, and I would like to highlight here especially the fantastic group of students who have joined us and are contributing greatly to our mission. The pictures below show them hard at work on their various watch duties, seemingly enjoying the experience (or at least faking it really well).
University of Miami graduate students Greg Koman and Tiago Bilo running some salinity samples. (NB: its not really as fun as they are making it look.)
Utrecht University graduate student David Wichmann, with SAMS ocean chemist Jeanne Castille.
Graduate students Roos Bol from NIOZ (left) and James Coogan from SAMS (right), at the CTD computer console.
Below are some other assorted photos from the cruise showing the science labs and work taking place on deck.
Recovery of a “sound source” for the acoustically tracked RAFOS floats deployed during OSNAP. Not in bad shape after four years in the water! (From left to right: R/V Armstrong bos’n Scott Loweth, U. Miami mooring technician Mark Graham, and NOC mooring technician Robert McLachlan.)
A mooring top float coming aboard in an early morning recovery.
U. Miami mooring technician Adam Houk with all his “ducks” (SeaBird micocats) in a row.
NOC mooring technician Chris Crow preparing instruments for deployment.
Femke de Jong and NIOZ mooring technician Lorenz Boom in the main lab discussing upcoming mooring operations.
Yours truly on deck trying to look like I am actually doing something worthwhile.
