New ICES ocean climate and atmosphere report published

The ICES Working Group on Ocean ​​Hydrography (WGOH), of which I am a chair-invited member, has just published its annual report on North Atlantic ocean conditions in 2018.  The report comprises several dozen multi-year time series of ocean observations around the North Atlantic Basin, which together paint a coherent picture of the current status of the ocean climate:  https://www.ices.dk/news-and-events/news-archive/news/Pages/Ocean-climate-2019.aspx

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North Atlantic ocean conditions 2018

In 2016, freshening of the upper ocean (0–1000m depth) was observed in the eastern subpolar North Atlantic. This decrease in salinity has since expanded northwards into the Nordic seas, influencing the Greenland Sea and northern Norwegian Sea to Fram Strait, as well as the southern reaches of the Barents Sea. Freshening is also observed spreading westward into the Irminger Sea and eastward into the North Sea.

Throughout the subpolar region, freshening is accompanied by moderate cooling at just a few sites, indicating that the large changes in salinity are dissociated from changes in temperature.

Freshening of central waters in the northeast Subtropical Gyre and intergyre region (Bay of Biscay, West Iberia, Gulf of Cadiz, and Canaries) was enhanced and extended deeper into the water column. In contrast to northern regions, temperatures here decreased in concert with freshening, thereby conserving water mass properties.

Coupled with atmospheric conditions, sea surface temperatures (SST) exhibited a tri-pole pattern, with warm conditions in both the subtropical and Nordic seas regions and cooler conditions in the subpolar region. A cold anomaly observed in the surface and upper ocean of the central subpolar North Atlantic intensified and expanded after weakening in 2017.

The Scotian and Northeast US shelves were warmer than normal, accompanied by notable freshening at several sites.

Extremely warm temperatures were observed near the surface in spring–summer across the Baltic Sea and the North Sea (> 1.5˚C than normal), with less pronounced warming observed from Biscay to Ireland (0.5–+1.0 ˚C).

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New paper: “Wintertime Fjord-Shelf Interaction and Ice Sheet Melting in Southeast Greenland”

A computer simulation of the ocean around Greenland was used to study the movement of water in and out of a large fjord. This is important because warm water that gets into the fjord may come into contact with the Greenland Ice Sheet and cause it to melt. The simulation indicates that a significant amount of warm water comes into contact with the ice during the winter. This was previously difficult to measure because of the difficulties in taking direct measurements of the water during the Greenland winter.

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Time-averaged wave energy flux through cross-sections of Kangerdlugssuaq Fjord.  In short, there’s more going in than coming out!
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Oscillations in the thermocline in the fjord over time, showing the impact of large amplitude coastally-trapped waves on water temperatures.

This work was based on Dr Neil Fraser’s PhD, but the model was forced using realistic winter wind conditions rather than idealised wind.  This was the first time (for me) that using Paraview to analyse model data in 4D has led or contributed to a publication.

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Kangerdlugssuaq Fjord, taken during Prof. Mark Inall’s 2010 field work. (c) SAMS

Fraser, N. J., Inall, M. E., Magaldi, M. G., Haine T. W. N. and Jones S. C. (2018). Wintertime fjord-shelf interaction and ice sheet melting in southeast Greenland. JGR: Oceans, https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014435

New paper: “Cross-slope flow in the Atlantic Inflow Current driven by the on-shelf deflection of a slope current”

Highlights

  • Slope water has been tracked on the European Shelf using drifters and gliders.
  • The deflection onto the shelf is not captured in models.
  • The slope water has a higher nitrate concentration that the shelf water, and supplies nutrients to the shelf.
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(a) pathway of the shallow drifters over the first 45 days after their release, in grey. The thick black trajectory shows the time mean line, from which the local across and along flow directions are derived. The local bathymetry is shown by thin black lines and Coriolis parameter/depth (f/h) contours by dashed lines. Location A is the point at which the shallow drifters stagnated and turned to cross f/h contours.  (b) The trajectories of all of the drifters throughout their active periods, shaded by the date. Location C shows the drifter release point, Location D shows where the deeper drifters crossed onto the shelf and Location B where the deeper drifters re-joined the slope.

 

Porter, M., Dale, A., Jones, S.C., Siemering, B., Inall, M.E. (2018). Cross-slope flow in the Atlantic Inflow Current driven by the on shelf deflection of a slope current. Deep-Sea Research Part I, in press.  doi:10.1016/j.dsr.2018.09.002

New paper published: “Decadal variability on the Northwest European continental shelf”

Jones, S., Cottier, F., Inall, M., & Griffiths, C. (2018). Decadal variability on the Northwest European continental shelf. Progress in Oceanography, doi: 10.1016/j.pocean.2018.01.012

https://doi.org/10.1016/j.pocean.2018.01.012

This paper details one of the key outcomes from my PhD so it was good to get it finished!  It describes how wind acting over the shallow seas west of Scotland can change the origin of waters on the inner continental shelf (and the coast).  This region typically recieves a mix of salty, nutrient rich water from the Atlantic and fresher, relatively nutrient poor water from the Irish Sea.  1-2 months of sustained easterly winds can block the inflow of Atlantic water and drive a pulse of Irish Sea water into the region, potentially importing much greater abundances of Irish Sea organisms and pollutants than during a typical year.  This body of water is detectable on the continental shelf for several months before it it fully displaced northwards.  Conversely, sustained winter storms can drive Atlantic water far onto the shelf and block the outflow from the Irish Sea, bringing oceanic conditions to what would normally be considered coastal locations.  The strong variability which results is roughly an order of magnitude greater than the changes seen in the adjacent Northeast Atlantic so is thought to mask the well documented decadal changes in these waters.

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Map of waters off western Scotland.  Black rectangles show the position of Ellett Line stations on the continental shelf.
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Time series of surface salinity from Ellett Line stations on the continental shelf.  x-axis depicts longitude, between the shelf edge (left) and the Scottish coastline (right). (a) shows surface salinity, where brown colours indicate high salinity oceanic water and blue shows lower salinity coastal water. (b) shows the mean salinity across the shelf for each year.  (c) shows the salinity anomaly calculated by subtracting the mean of each station from the data, and (d) depicts the mean surface salinity for each station.  The grey region gives the standard deviation of the data which is a measure of the variability present.

Winning video and overall competition winning entry – ARCHeR

My animation of FVCOM model output won the 2017 ARCHeR image and video competition.  ARCHeR is the largest Cray supercomputer in the UK, and its supercomputing service was used by Dr Dmitry  Aleynik (SAMS) to run a series of simulations of waters off the west coast of Scotland.  I used the output of these model runs to create the animation using Paraview.

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Link to the ARCHeR competition gallery here.

Learn more about my work on data visualisation here.

References:

1 Aleynik, D. Davidson, K., Dale A. C., Porter, M. (2016) A high resolution hydrodynamic model system suitable for novel harmful algal bloom modelling in areas of complex coastline and topography. Harmful Algae, 53(3):102–117, 10.1016/j.hal.2015.11.012

 

SAMS Magical Mystery Tour… part 1

There are numerous projects and facilities within SAMS that are a mystery to many staff outside specific departments. I thought it might be nice to have an occasional informal show-and-tell with a general staff invite, whether it be an interesting experiment, piece of equipment or entire enigmatic wings of the building.

For a start, Professor Mark Inall kindly offered to do a demonstration of the fjord tank .

We had a great turnout, with two sittings to accomodate everyone. Based on the success of this session we’ll definitely do another one fairly soon. A couple of photos below showcasing the tank and Mark’s smashed finger!

Open day at the SAMS Ocean Explorer Centre

On the weekend of the 27/28th SAMS organised a series of outreach and public engagement activities. I set up an exhibition based on the SAMS Marine Robotics Facility, and featuring several of our underwater vehicles. It’s rare that the public gets to see the robots in the flesh, so it was nice to show them off and answer a range of interesting questions.

A couple of photos courtesy of Raeanne.

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Showing off the SAMS underwater robotics cabability at the OEC open day, May 2017
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Showing off the SAMS underwater robotics cabability at the OEC open day, May 2017

Hydrofoil surfboard

I thought I would share some pictures of a recent project to build a hydrofoil for a kitesurf board.  Public awareness of hydrofoils has increased since their adoption by Americas Cup catamarans but very simply they are just a wing which is designed to lift in water.  For this project, the aim is to generate enough lift to raise the board and rider out of the water, allowing a completely smooth and almost frictionless ride.  This means that you can kitesurf in very light winds at up to 3 times the windspeed.  Kite foilboards are increasingly being used for racing, but my interest was more in its freeride potential for exploring the flat waters around Oban.

I decided to modify a kite surfboard to suit the foil, but wanted to retain the ability to remove the foil and use it as a regular board when the conditions suited.  Consequently the foil is mounted using a strong carbon plate attached to the board by 4 bolts.  To spread the load a little more, a glass-fibre plate is also mounted top and bottom.

The forces through the vertical mast are huge, so for this version I bought a pre-made aluminium mast online.  The baseplate and wings bolt on to this.  I thought this modular approach might come in handy if I decide to build higher performance wings at some point.

As of writing this article I’ve had six sessions with the board and am now reasonably confident at flying it on both tacks.  The initial learning curve is very steep and involves a lot of crashes, but it’s been worth the effort.  When you get up on the foil the feeling must be similar to a seabird skimming the surface; completely smooth and silent.  It’s also very clear that you’re flying a tiny, sensitive airplane through the water, and the muscle memory to control the height takes some getting used to.  But it’s very addictive!

Edit: Now have a short clip of it in action: https://www.youtube.com/watch?v=VLkVU4_AP7M