Category Archives: News

Stories in Greenlandic Place Names along the Southeast Coast (Straneo OSNAP AR69-03)

The R/V Armstrong along the southeast Greenland coast. Drone photo by Croy Carlin.

By Aurora Roth

On September 1, almost halfway through the cruise, we passed through Ikerasassuaq (“big sound”, alternately known as Prince Christian Sound). It’s a long narrow channel that demarcates the north end of Uummannarsuaq (“large heart-shaped place” or Cape Farewell), at the southern tip of Kalaallit Nunnat (Greenland). Travelling through this fjord marked our transition from work on the southeast coast and the Cape Farewell mooring array to work on the southwest coast and the Labrador Sea mooring array. Until this, we had been moving up and down the southeast coast (see map for cruise track), completing hydrographic surveys, taking water samples, and replacing long-term instruments that will live in the depths of the ocean taking measurements for the next two years. The coasts, seas, glaciers, histories, and settlements of the southeast and southwest regions are wildly different, and going through Ikerasassuaq felt like going through a portal to a different world.

Map of South Greenland showing some Greenlandic place names discussed in this post. Colors indicate sea floor bathymetry (from BedMachinev4 (Morlighem et al., 2017)) and show troughs extending from fjords on the continental shelf. Blue stars indicate towns. White is the Greenland Ice Sheet extent and grey is ice-free land above sea level. Red dots show Cape Farewell Mooring Array (on the east) and Labrador Sea Mooring Array (on the west). Map created with the help of Jamie Holte.

We followed a cargo ship into Ikerasassuaq, bound for Qaqortoq (“white”), the largest town in the south of Greenland. We saw the lights of Aappilattoq (“the reddish place”), the first town we’ve seen as we stopped in the sound for the night. In contrast, the southeast coast has no towns, though there are archeological sites of older settlements. The southeast coast, with its steep mountains and glaciers plunging into the ocean, isn’t the best place for permanent towns, but it used to be travelled often by people from further north around Ammassalik (“the place with capelin”). From Ammassalik, people would travel south and around the bottom of Greenland to the west coast to trade and meet up with West Greenlanders. As the east coast was colonized, a Danish trading post and mission were set up in Ammassalik. Travelling along this part of the southeast coast stopped as trading with Denmark replaced travelling to trade with West Greenland. As a consequence, East Greenlanders became even more isolated from the populous western side (Gulløv 1995). Now, the few people that follow this coast and navigate around the icebergs here are from adventure sailing and climbing expeditions and the occasional research vessel, like us. For almost two weeks we didn’t see any other vessels. There is also a lasting separation between East Greenland and West Greenland, and East Greenlanders are often marginalized, with less access to resources, fewer education opportunities, and less power in the national government.

The R/V Armstrong making our way through narrow Ikerasassuaq – moving from the southeast coast to the southwest coast.

I’ve been wondering what knowledge, place names, and connections have been lost here along this stretch of coast as a result of colonization. Documented Greenlandic place names are sparse here, but what I could find (mostly from a report by the Danish Geodata Agency, reviewed by Oqaasileriffik, the Greenlandic Language Secretariat) made this coast feel more animated. The place names show how Greenlanders gave their attention to and were in a relationship with this stretch of coastline – Timmiarmiut fjord and glacier means “habitation of the birds”. Sikuijivitteq means “where it is never free of ice”. Puisortoq glacier means “how often something comes to the surface” but also “puisi” is a word for seal and perhaps this is related? Anoritooq glacier and fjord, meaning “where it is very windy”.

Our furthest north point was Timmiarmiut fjord. We surveyed the underwater trough that extends beyond the fjord onto the continental shelf. This trough, and others like it, were made over 10,000 years ago when the sea level was lower and glaciers of the ice sheet extended further. After sending our instruments down into the water above the trough, we watched squiggly lines form on the screens in the lab. These data tell us that cold water with a temperature below 0°C was following the trough out into the ocean but near the surface, and warmer water (3-4°C) from the North Atlantic and Gulf Stream was flowing into the bottom of the trough. We call the cold water “Polar Water” and it’s a mix of glacial ice melt, sea ice melt, and water from the Arctic Ocean. Its freezing point is below 0°C because it’s salty ocean water despite being less salty than other ocean waters. The Polar Water and warmer Atlantic water come together and intermingle at different depths, trying to figure out where to go as they meet each other and mix. We collected data at other fjord outlets and troughs as we came back south along the coast. Each time we saw this layering of colder, fresher water, sitting above warmer, saltier water and saw thin layers of each water type trying to weave together. The outcome of this meeting and weaving is what controls how much warm water can come into fjords and contact glaciers causing further melt, and how much glacial meltwater can then come out of fjords and mix into the North Atlantic Ocean, affecting large-scale ocean currents and climate.

From velocity measurements taken with Acoustic Doppler Current Profilers (ADCPs), we started to map out how these troughs make the East Greenland Coastal Current wiggle and turn, further complicating this meeting of different waters. Even when hundreds of meters deep, the ocean can “feel” the bottom topography and responds to it by changing course. Sometimes in the data, we could see eddies generated from the troughs that were swirling in circles, causing water to mix. To make things even more complicated, we experienced two days of strong winds while collecting data. The winds pushed the surface of the ocean around causing waves and more mixing of water. When the winds blow from north to south, this sets up the physics of the ocean to push the warmer water closer to the coast. When I step back and take this all in, there is so much movement and action at every scale. Everything affects everything else. It’s sort of amazing that we can make any sense of the data we collect at all, that we can figure out stories of what’s happening here and why it matters.

Many of the glaciers along the southeast coast have transitioned in the last two decades from ending in the ocean to now ending on land, retreating up into valleys, deflating from their moraines, and separating into different branches. When a glacier loses its direct connection with the ocean, it changes how the glacier meltwater mixes nutrients into the ocean and it changes the marine ecosystem. One of the things we’re doing on this cruise is collecting water samples to analyze for nutrients (like nitrate, phosphate, silicate, etc) to understand this story better. The Greenlandic place names speak to these ecosystems supported by glaciers, of the birds and seals (even the winds which are impacted by glaciers). I wonder how long the place names that remain will continue to describe these places, or even if they still do.

We are here now in Kalaallit Nunaat, as western-trained scientists trying to understand certain stories of this place. Greenlandic people and culture have stories of this place too that are equally important. Sometimes glimpses of those stories are found in the Greenlandic place names. The small act of putting in effort and time to figure out place names, and use them in conversation, outreach, or academic publications, is a small act of acknowledging Greenlandic presence and relationship here. It’s also an act that acknowledges what was violently lost due to colonization and what stories and names have persisted despite it.

Learn More

Greenland Pilot – Explanations of the Place Names from the Danish Geodata Agency

More on Greenlandic Place Names


Hans Christian Gulløv. Olden times in Southeast Greenland: New archaeological investigations and the oral tradition. Études Inuit Studies Vol. 19, No. 1, Archéologie, Art, Ethnicité (1995), pp. 3-36.

Morlighem M. et al., (2017), BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation, Geophys. Res. Lett., 44, doi:10.1002/2017GL074954,

Aboard the R/V Neil Armstrong

By Bill Johns, Chief Scientist

Our cruise is now about halfway through, and spirits are high as we steadily make progress on accomplishing our cruise objectives.  Yesterday the final University of Miami mooring was deployed in the Iceland Basin, completing the turn-around operations on all of the seven moorings deployed along the eastern flank of the Reykjanes Ridge. We have now turned the mooring operations over to the NIOZ team, who at this moment are deploying their westernmost Irminger Sea mooring (see photo), and if all goes well will follow that with the deployment of their second (of five) moorings this afternoon. 

It is a rather nice morning in the Irminger Sea, with relatively calm conditions and the sun even peeking through the clouds from time to time. Apart from a following swell that is occasionally putting some water on the aft deck, it is a fine day for mooring work, seriously challenging our usual mantra that “it is nicer in the Iceland Basin”. Our mooring operations there were mostly in overcast and often cold, drizzly conditions and so the weather today in the Irminger Sea is a pleasant surprise (however, not to be discussed further..).  The only major glitch we have encountered so far is that one of the U. Miami moorings unexpectedly returned to the surface after its deployment, while communicating with the acoustic mooring releases to put them into “sleep mode” for the next two years until we come back again, and that mooring had to be recovered and redeployed again, basically costing us a day of ship time.  This is one of the reasons, besides unpredictable weather, that we build a little extra time into our cruises for contingencies.

The U.S. and Dutch teams continue to work very well together, and this is particularly evident on deck during the mooring operations.  During the first half of the cruise, when the U. Miami mooring work was taking place, the two lead technicians from NIOZ (Leon Wuis and Toon Koopman) ran the mooring winch for the U. Miami team, who were busy loading instruments and floats onto the mooring line as it was paid out.  Now the lead U. Miami technicians (Eduardo Jardim and Cedric Guigand) are doing the same for the Dutch team as they recover and deploy their moorings.  It is always interesting to see how different research groups approach their mooring operations, with somewhat different mooring designs and different methods of deployment. For example, the NIOZ team uses a “mooring table” (pictured in the photos) that has a built-in stopper system for changing mooring wires and attaching instruments, whereas for the U. Miami moorings this is all done at deck level using a traditional double line stopper system.

The mooring winch system we are using is a specially designed system called a LEBUS (aka “double barrel”) winch system (see photo) that is somewhat complicated but highly efficient for performing rapid mooring turnaround operations. It takes two people to run it with a third assisting, and with at four people on the aft deck making mooring connections, and several others bringing instruments in and out from the lab, it requires a large team and a carefully choreographed operation.

With the change-over in mooring operations, the night-time CTD watches have also changed at mid-cruise to free up personnel from the Dutch team for their mooring work.  During the first half of the cruise, these watches were mostly manned by NIOZ scientists but now they are being mostly manned by the U. Miami team.  Everyone is adapting to these changes well and pitching in wherever needed. It has been a great pleasure sailing with this entire team thus far, and – as we often say – “so far so good”, with our fingers crossed.

A new tool to compare models and observations

A simple Python code that computes the meridional overturning circulation (MOC) from a model dataset interpolated onto the OSNAP section. More information can be found on the o-snap website under the tabs Outreach/For Modelers and the code can be downloaded here.

Call for Abstracts: AGU Fall Meeting Session “OS026 – Variability and controls of ocean climate revealed by long-term multidisciplinary eulerian observatories”

Dear colleagues,

We are pleased to invite you to submit an abstract to the session: Variability and controls of ocean climate revealed by long-term multidisciplinary eulerian observatories that we have prepared at the next AGU Falll Meeting, which will take place on 12-16 December 2022 in Chicago (in person and virtual participation).

The deadline to submit your abstract is *3 August (23:59 EDT/03:59 GMT)*, instructions are found here.

We hope to meet you virtually or in person in December. Please don’t hesitate to forward this call to other colleagues who may be interested.

Raquel, Elizabeth, Yao and Dariia

*OS026 – Variability and controls of ocean climate revealed by long-term multidisciplinary eulerian observatories*

The global ocean absorbs, stores, and redistributes vast amounts of heat and carbon and is therefore the main driver of climate regulation. It means that human-induced forcing is superimposed on ocean natural variability, and that this variable forcing involves complex interactions and feedbacks of physical, chemical and biological processes from the air-sea interface to the sea-floor. To understand these complex relationships between ocean processes, their forcings, and effects, long term time-series of Essential Ocean Variables (EOV) from fixed point (Eulerian) multidisciplinary observatories, monitoring processes that take place over much shorter periods of time, are critical.

In this session, we aim to share most recent research based on long term OceanSITES data sets or on long term time-series from eulerian multidisciplinary observatories not included in the network addressing air/sea exchange processes such as heat and freshwater fluxes, and ocean carbon and oxygen update; ocean transport, but also other biogeochemical, biological, and deep ocean processes. We welcome contributions which describe ocean variability at different time-scales from large-scale climatic fluctuations to hurricanes, and examine their governing mechanisms and environmental implications. Submissions focused on processes-oriented studies integrating different observing platforms (e.g. satellite, Argo floats, gliders, …) with long-term eulerian observation (moorings, ship-based time-series) are also encouraged as well as studies combining observations and modelling.

*Conveners:*Raquel Somavilla (Spanish Institute of Oceanography), Elizabeth Shadwick (CSIRO Marine and Atmospheric Research), Yao Fu (Georgia Institute of Technology), and Dariia Atamanchuk (Dalhousie University)

*Index Terms: *4215 Climate and interannual variability, 4805 Biogeochemical cycles, processes, and modeling, 4504 Air/sea interactions, 4532 General circulation

Extended OSNAP overturning time series for 2014-2018

As revealed by the first 21-month record (2014-2016) from the OSNAP array [Lozier et al. 2019], the subpolar overturning occurs primarily in the eastern subpolar region of the North Atlantic Ocean.  This finding contrasts the view of Labrador Sea variability dominating the overturning circulation variability across a range of latitudes via the southward propagation of density anomalies formed by convection in the basin interior.  The small overturning in the Labrador Sea was surprising since there was strong convection in the Labrador Sea during the 2014-2016 winters.  However, given the scale of the expected delay in the overturning response, the 2014-2016 time series may have been too short to pick up this response.  In short, the signals in the Labrador Sea may take a few years to imprint on the OSNAP array.

Continuous observations from the OSNAP array are now available for a 4-year period.  The 4-year time series (2014-2018) of the estimated overturning across the section is shown in the figure below.  Here the strength of the overturning circulation is defined as the maximum of the streamfunction in density coordinates, and is estimated across the full array, OSNAP West (Labrador Sea) and East (eastern subpolar gyre between Greenland and Scotland), separately.  As shown in Lozier et al. [2019], this decomposition allows us to make relative comparisons of the overturning contributions within the subpolar subbasins.  Clearly, there is a consistent pattern throughout the records: the overturning circulation takes place primarily across the OSNAP East section in the eastern subpolar region.  The extended time series proves the validity of the first 21-month record and supports a diminish contribution from the Labrador Sea, over the observational time scales. 

30-day time series of the strength of the meridional overturning circulation (MOC) across the full OSNAP array, and the OSNAP East and West sections, separately. Shading indicates the uncertainty in each 30-day estimate, obtained from Monte Carlo simulations. The 4-year mean MOC is 16.6 Sv# (uncertainty of 0.7 Sv; standard deviation of 3.5 Sv) across the full array, 16.8 Sv (uncertainty of 0.6 Sv; standard deviation of 2.8 Sv) across OSNAP East, and 2.6 Sv (uncertainty of 0.3 Sv; standard deviation of 1.2 Sv) across OSNAP West. # 1 Sv= 106 m3 s-1

Further analysis has been performed to assess the role of Labrador Sea and Irminger Sea convection in creating western boundary density anomalies in the region and the contributions of those boundary anomalies to the subpolar overturning variability [Li et al. 2020].  Results from this analysis shed light on the causes of North Atlantic overturning variability downstream from the subpolar region.

Of course, a question remains as to which subpolar basin(s) holds the key to the overturning variability over interannual and longer time scales.  Needless to say, maintaining high-quality trans-basin observations is critical for tackling this question.

Finally, we are pleased to announce that all of the seven 2020 OSNAP cruises have been carried out successfully. Special thanks to the PIs from the observational groups who worked tirelessly in (re)planning the cruises to accommodate the extraordinary challenges caused by the pandemic.  All cruises had to reduce their working time at the mooring sites because of the need for more transit time to and from their home port.  All observational groups outperformed expectations: everyone was safe and the data return was superb.  We also applaud the captain, the crew and everyone on the science teams!  With all of these efforts, we will be adding another two years of transport estimates in 2021 without significant delays.



Lozier, M.S., F. Li, S. Bacon, F. Bahr, A.S. Bower, S.A. Cunningham, M.F. de Jong, L. de Steur, B. deYoung, J. Fischer, S.F. Gary, B.J.W. Greenan, N.P. Holliday, A. Houk, L. Houpert, M.E. Inall, W.E. Johns, H.L. Johnson, C. Johnson, J. Karstensen, G. Koman, I.A. Le Bras, X. Lin, N. Mackay, D.P. Marshall, H. Mercier, M. Oltmanns, R.S. Pickart, A.L. Ramsey, D. Rayner, F. Straneo, V. Thierry, D.J. Torres, R.G. Williams, C. Wilson, J. Yang, I. Yashayaev, J. Zhao, A Sea Change in Our View of Overturning in the Subpolar North Atlantic, Science, 363(6426), 516-521 (2019). 

Li, F., M.S. Lozier, S. Bacon, A. Bower, S.A. Cunningham, M.F. de Jong, B. deYoung, N. Fraser, N. Fried, G. Han, N.P. Holliday, J. Holte, L. Houpert, M.E. Inall, W.E. Johns, S. Jones, C. Johnson, J. Karstensen, I.A. LeBras, P. Lherminier, X. Lin, H. Mercier, M. Oltmanns, A. Pacini, T. Petit, R.S. Pickart, D. Rayner, F. Straneo, V. Thierry, M. Visbeck, I. Yashayaev, C. Zhou, Subpolar North Atlantic Western Boundary Density Anomalies and the Meridional Overturning Circulation, submitted to Nature Communications (2020).

OSNAP/NIOZ Cruise Blog

OSNAP scientist, Femke de Jong, and a team of NIOZ scientists are currently at sea on a research cruise aboard the RV Pelagia. They will be servicing moorings and deploying drifters in the Irminger Sea. Follow their progress on the cruise blog posted here.

Update on OSNAP Floats

by Amy bower

While the rest of the OSNAP team has been busy preparing the first continuous time series of the AMOC in the high-latitude North Atlantic from the OSNAP array measurements (link to Science paper), the Bower Lab has been steadily processing data from more than 120 deep-sea floats that were released in the deep currents of the AMOC between 2014 and 2017 as part of “OSNAP Floats”. These so-called RAFOS floats (RAFOS stands for RAnging and Fixing Of Sound) were tracked continuously underwater using an array of 13 moored sound beacons spread throughout the subpolar region. Once a day during each float’s mission, the float “listened” for signals from the sound beacons, and internally recorded the time it heard each one (usually only 2-4 beacons were in range on any given day). After two years of collecting these “times-of-arrival” from the sound beacons, each float dropped a ballast weight, popped to the surface and transmitted all its stored data via satellite. We have been reconstructing each float trajectory by converting the acoustic travel times to distances, and triangulating float position for every day. It is always an exciting moment when the complete trajectory pops onto the computer screen, usually revealing some incredibly interesting pattern of the flow deep in the ocean.  

Nearly every diagram of the pathways of the lower limb of the AMOC in the subpolar North Atlantic show continuous lines of flow snaking around the rim of its three sub-basins:  the Labrador, Irminger and Iceland Basins (e.g., Fig. 1). This view of the deep circulation has been shaped largely by our observations of the subpolar ocean around its edges, which almost all show a relatively strong deep boundary current transporting modified versions of the dense overflows (Iceland-Scotland Overflow Water and Denmark Strait Overflow Water) that feed the lower limb of the AMOC. When we track the pathways of individual fluid parcels, or large groups of them, we see a somewhat different view of the pathways of the deep AMOC (Fig. 2). This “Lagrangian” view—by which we mean the ocean circulation as observed by following individual fluid parcels, in contrast to the “Eulerian” view, which is constructed from current measurements at fixed locations—highlights the turbulent nature of the currents in some regions of the deep ocean. The float trajectories show a much messier view because deep ocean currents are not always orderly streams of water flowing smoothly along, but rather consist of blobs or patches of water 10-100 km in diameter swirling around like slow-motion hurricanes.

In some regions, the Lagrangian and Eulerian views look similar, at least on the large scale. For example, most (but not all) of the floats released east of Greenland more or less follow the boundary around the southern tip of Greenland. In other regions, however, the boundary-following pipe-like view seems completely inadequate to describe the deep pathways of the AMOC. For example, floats coming through the Charlie-Gibbs Fracture Zone (a deep gap in the mid-Atlantic ridge that separates the Iceland and Irminger Basins) do not, in general, follow the boundary of the Irminger Basin. Instead, the floats spread westward and even southward in a somewhat chaotic fashion. Also, some floats released in the deep boundary current transporting Iceland-Scotland Overflow Water southward in the Iceland Basin never make it to the Irminger Basin through gaps in the ridge, but instead drift southward within the eastern North Atlantic, apparently having escaped from the deep boundary current system altogether.

So why do we care what pathways these deep waters take? For one practical reason—if we want to accurately monitor the strength of the deep AMOC, we better have a good idea where its major branches are so we can place our instruments judiciously. Also, the pathways of these deep water masses have an impact on how they are modified. A branch that carries deep waters along a slow, meandering interior pathway may lead to more stirring and modification of the water properties than would occur along a more direct, boundary-following path. This in turn affects how heat and other properties are re-distributed throughout the ocean.

The Bower Lab is looking forward to the upcoming General Assembly of the European Geosciences Union in Vienna, Austria next week, where we will have the opportunity to showcase the many and varied discoveries emerging from OSNAP Floats.

Fig 1. Recent diagram illustrating the circulation of the deep currents of the subpolar North Atlantic, From Daniault et al. (2016)

Fig. 2:  Trajectories of 123 RAFOS floats, tracked at depths from 1800 m to 2800 m between 2014 and 2018. Colors indicate individual float tracks.


Daniault, N. et al., 2016. The northern North Atlantic Ocean mean circulation in the early 21st century. Progress in Oceanography 146, 142-158

Modelling in the Labrador Sea

by Clark Pennelly

The Labrador Sea in the northwestern Atlantic Ocean is a bit like salad dressing: the multiple water layers present will not happily mingle with others nearby, just like oil and vinegar. Of course, this all changes when the salad bowl that is the Labrador Sea gets stirred up! Strong winter storms pass through the Labrador Sea, cooling the surface water and making it more dense. Should this cooling process continue, the density will increase until the surface layer will have the same density as the subsurface layer, allowing them to efficiently mix together – just like shaking a bottle of dressing. We call this ‘shaking’ deep convection.

However, the Labrador Sea is not simply a 2-ingredient salad dressing mixture. A fresh and cold water cap is at the surface; this water originates from the Arctic and could be from melting of Greenland glaciers, sea-ice from the Beaufort Sea, or even runoff from one of the many rivers which discharge into the Arctic Ocean from Canada, northern Europe, and Russia. A warm and salty layer of water from the Atlantic Ocean exists below this. Further below is yet another water mass which is cold and salty, a product of mixing the two layers above it during the cold winter; we call this layer Labrador Sea Water. There are even more layers beneath, but I won’t get into them for now. These top three layers are important to the deep convection and water mass formation that previous blog posts have discussed.

My PhD thesis revolves around the ocean layers within the Labrador Sea and how they are modified by a variety of sources, such as an input of freshwater, heat, or perhaps changes in the weather. As this region is notorious for its rough seas, particularly during the stormy winter, research cruises (see ) tend to occur/gather data after the winter has passed when seas are calmer and the 12-point Beaufort sea state scale (see goes from 10’s and 11’s down to more manageable single digits. Unfortunately, research cruises may therefore miss clues about the mixing and formation of water layers that happen during the convective season. I use computer models to investigate what may be occurring when research cruises are not around to gather data. While they are not without their own set of problems, models allow us a peek into the unknown from the comfort of a Beaufort 0 sea-state office.

One portion of my research explores rotating circular features, which we call eddies, that form off the west coast of Greenland. These eddies are produced via changes in the seafloor nearby. As the West Greenland Current moves alongside the west coast of Greenland, it carries both fresh and cold water at the surface as well as salty and warm water below. These eddies carry both water layers away from the coast and into the heart of the Labrador Sea. Both of these water masses impact the Labrador Sea in a different way, so these eddies are rather interesting and important features. However, these small events are notoriously difficult to represent within numerical models, especially multi-decade simulations. We had to get a little creative in order to make sure we would resolve these eddies as modelling such eddies requires a lot of computing resources. We set up a complex simulation which has a resolution of 1/60 of a degree, meaning this simulation should be able to resolve features where are larger than a few kilometers. The simulation requires over 600 CPUs and about 72 hours of real time to produce 40 days of simulation time. To put that into perspective, our regular simulations may use 60 CPUs and finish 2 years of simulation time in 72 real hours; quite the difference! We are interested in running this expensive simulation across 17 years, from 2002 to 2018, so we can capture variability across many years, though some quick math says that this simulation will take about a year to finish. But what do we gain by resolving the Labrador Sea at high resolution?

Well-defined eddies is what we get! You can see those individual eddies within the red circle. From running this model we’ve so far learned that those eddies can last up to two years, meaning that as they travel southwest from the coast of Greenland they may encounter multiple winters and therefore be involved in multiple rounds of deep convection. I’m currently exploring how these eddies evolve through their lifetime in the Labrador Sea. We know they bring substantial heating into the region, limiting deep-water formation. Thus being able to detect them with our model is crucial in order to achieve an accurate spatial representation of convection. Lower resolution simulations may fail to resolve these features and thus their importance. Since they persist for multiple convective years, they may have a more complicated story than previously thought which I hope my research will help uncover. Numerical modelling allows for the scrutiny of such events as observations within the Labrador Sea may not provide the full information we seek.

Arctic freshwater storage and export – what will it mean for the AMOC?

by Helen Johnson

with input from Sam Cornish and Yavor Kostov

The first results from the OSNAP array, published this month in Science (, are incredibly exciting! Over the 21 months of data collected so far, it has been the conversion of warm, salty, shallow Atlantic water into colder, fresher, deep water east of Greenland that has dominated the overturning circulation and its variability.  This challenges the prevailing view that deep water formation in the Labrador Sea to the west of Greenland is the major player in determining overturning variability.  And it gives us some clues about how changes further north, in the Arctic Ocean, might affect things.

A major motivation for measuring the overturning circulation with the OSNAP and other observational arrays arises from the expectation that the overturning will change as a result of human-induced climate change. The overturning circulation is predicted to weaken over the coming century, due to a warming and freshening of the high latitude North Atlantic. Part of the freshening expected in these critical deep water formation regions is due to changes in the amount of freshwater exported from the Arctic to the Atlantic, on both sides of Greenland. The Arctic Ocean has recently accumulated a large amount of freshwater, but we do not know if or when it will be exported to the Atlantic, or at what rate.

My group in Oxford have been investigating changes in the amount of freshwater stored in the Arctic, and the reasons for them, in the hope that this will teach us something about the changes we might expect in freshwater export ( We have deduced the relationship between winds over the Arctic and total Arctic freshwater storage in a climate model. We now know that if the winds over the Arctic change, it takes the system at least a decade to come into a new equilibrium, with a different amount of freshwater stored.  Based on the relationship we deduce between winds and freshwater content, we estimate changes in Arctic freshwater content over the last century – and our time series agrees well with the limited observational data available (see figure), giving us confidence that the relationship is a useful description of the real world!

Our results suggest that the large increase in Arctic freshwater content since 1992 can largely be explained by historical changes in the winds driving the Arctic Ocean circulation (although we can’t rule out a smaller contribution from sea-ice melt).  What’s more, this increase doesn’t seem exceptional compared to variability in our time series over the rest of the century, suggesting that it may simply be natural variability.

Of course, changes in freshwater exported from the Arctic, natural or not, still have the potential to affect the overturning circulation! The long memory of atmospheric conditions revealed by our results is important because, provided we know what the winds have done, we can potentially predict changes in Arctic freshwater content a few years ahead. Based on our work so far, we expect Arctic freshwater content to decrease over the coming decade, and freshwater export to the Atlantic to increase.

The OSNAP array is ideally-placed to detect any impact of this change on the high-latitude overturning circulation. Based on the OSNAP results so far, we might expect that Arctic freshwater export through Fram Strait to the Nordic Seas (rather than through the Canadian Archipelago to the Labrador Sea) will have the most impact. So we have several hypotheses that our continued OSNAP observations and modelling efforts will put to the test in the coming years!

When science encounters art

by Femke de Jong

Collaborations in science are great, especially within a group as closely knit as OSNAP, but sometimes  the most surprising things come out of totally different kinds of collaborations. I saw beautiful examples of this in a special exhibit at the Boston Science Museum during my time as a postdoc at WHOI. Collaborations between scientists and artists led to new or different interpretations of the things we know. An example is the interpretation of the work of colleague Larry Pratt on turbulent torusses, the equations of which were somewhat intimidating in powerpoint presentations, but the art interpretation is beautiful and may even help us visualize those nasty equations.

photo from Larry Pratt’s website at

I recently got the opportunity to join a similar collaboration as this summer the island of Texel will host an art tour called S.E.A. or Science Encounters Art [link]. In this project, artist are paired with scientists from the Royal Netherlands Institute for Sea Research, also based on Texel. The artful interpretations of the scientist’s research will be displayed outdoors on the island for three months (an added complication on a windy island). Around these sculptures, other forms of art like performance and poetry, will also be featured. Since I might actually be around for most of summer this year (no OSNAP cruise for us) this sounds like a really cool thing to experience.

The particular collaboration I’m involved in at S.E.A. is a little bit special because it does not involve one artist. I was matched with a group of students at the Gerrit Rietveld Academy of Art in Amsterdam. At the start of this project, during a visit of students to Texel, I was invited to give a presentation about my research. I explained about the ocean circulation, the OSNAP project and showed some videos of how we go about doing measurements at sea. This resulted in a ton of further questions, which I was happy to answer. Alter that week the students presented their first thoughts on possible projects. For the students this is a learning experience as well as an art project as this is their first commissioned project. Besides coming up with an inspiring idea they need to think about practical realization, budgets, logistics (does anyone think this almost starts to sounds like organizing fieldwork…?). 

A few weeks after the first introductions I was invited to the Rietveld Academy to come and listen to the presentations of the students plans. It was great to hear the very different interpretations and links they had made. Plans varied from man-sized wavy blue slides that represented current motions (and may feature some during rainy days) to an ironic video documentary on fake science. Currently the students are working out their plans in more details to see which ones can be realized. There will not be enough space and money to accommodate all the student projects, but the plan is to build as many as possible. Next to the students I’m also working with Alkmaar’s city poet, Joris Brussel. I invite everyone to come see and read (or hear) the results on Texel this summer.