FASTNEt - Fluxes Across the Sloping Topography of the North East Atlantic

Lead Research Organisation: Bangor University
Department Name: College of Natural Sciences

Abstract

Shallow seas, the Shelf Seas, surround almost all of the Earth's land masses. On average shelf seas are hundreds of meters deep, compared to the average depth of the ocean of nearly four kilometres. Shelf Seas may be as narrow as a few kilometres, or as wide as hundreds of kilometres and together they occupy only a tenth of the watery part of the world. Yet they exert an effect on humanity far out of proportion to their mere size. Shelf Seas around the UK and western Europe are particularly wide (10s to 100s km) and shallow (around 150m); they are beset by strong tides, westerly winds, and fed by the warm waters of the NE Atlantic. From the smallest plant life, phyto-plankton, to the fish, UK Shelf Seas are highly biologically productive: nine tenths of the world's commercial fish catches come from shelf seas. This high productivity is fuelled to the greatest extent by the movement of nutrient-rich ocean waters onto the Shelf Seas. However, the step seabed slope (the Shelf Edge), which marks a narrow zone separating ocean from shelf, acts to reduce the movement of water from ocean to shelf (and visa versa); major ocean currents do not like to cross a sloping seabed. This restriction to exchange, however, breaks down when oceanic flows feel the wind or the seabed, or vary more rapidly than daily or over distances shorter that a few tens of kilometres.
The shelf edge is therefore seen as the controlling gateway to exchange between ocean and shelf, and the gatekeepers of that exchange are flows which change quickly, or lie at the very surface or at the very bottom of the sea. This makes the gatekeepers of exchange difficult to measure, and as a result we know very little about how the gatekeeper processes change from one season to another and from one year to another.
FASTNEt will bring together the strongest possible UK team of Physical Oceanographers to tackle this challenge using state-of-the art observational technologies, and a range of predictive modelling approaches.
Two research ship expeditions will study the details of the gatekeeper processes, aided by satellite tracked drifting buoy, fluorescent dyes, and unmanned mini-submarines. Instruments will be left in place over winter to record changes brought by winter storms, and a fleet of unmanned submarines will visit these instruments in conditions no ship could operate in, and is so doing fill a huge gap in our understanding.
We will take the information gathered from the submarines, drifters, satellite pictures and ships and test our understanding of the gatekeeper processes, improve models designed to simulate these processes. We will then work with the National Centre for Ocean Forecasting to help improve our ability to provide forecasts of the conditions of the seas surrounding the United Kingdom.

Planned Impact

see lead proposal

Publications

10 25 50

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Schindelegger M (2018) Can We Model the Effect of Observed Sea Level Rise on Tides? in Journal of Geophysical Research: Oceans

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Stephenson G (2016) Systematic Bias in Baroclinic Energy Estimates in Shelf Seas in Journal of Physical Oceanography

 
Description We now have a capability to accurately measure vertical mixing by using ocean gliders with specific turbulence equipment attached. Work from cruise D376 show that the Ocean Mixing Glider (OMG) produces very similar results to those obtained from conventional free falling profilers. This is significant step forward in our ability to obtain long-term observations of vertical mixing in the ocean.



This new data, together with other observations, has suggested that severe wind events may have an impact on the shelf sea vertical transports long after the wind have died down. This is because the wind changes the vertical temperature structure of the ocean and this affects how wave motions within the water column can move and how energetic they are.

We have also shown that there is a bias in calculations of internal tidal energy fluxes when the surface tide is too strong. This therefore applies to most observations in shelf seas. A correction is suggested.
Exploitation Route This new technique has lead to a capability to get continuous autonomous measurements of turbulence for several weeks, something which previously would have required a very large investment in trained staff.

The new energy flux result will be of importance for a wide international community, as evidenced by the interest for the owrk at conferences.
Sectors Aerospace, Defence and Marine,Environment

 
Description Deeming Summer Bursary
Amount £1,500 (GBP)
Organisation Bangor University 
Sector Academic/University
Country United Kingdom
Start 05/2014 
End 09/2014
 
Description Were tides resonsible for the low oxygen levels during the Turonian mass extinction? 
Organisation European Centre for Research and Teaching of Environmental Geosciences (CEREGE)
Country France 
Sector Academic/University 
PI Contribution Tidal model simulations to be used in a climate model of the Turonian (95Ma).
Collaborator Contribution The French team has provided bathymetry and stratification data for the Turonian, to be used in the tidal model i base my work on.
Impact none to date.
Start Year 2016
 
Description AGU OS 2018 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Gave three presentations at the 2018 AGU Ocean Sciences meeting, including work on deep-time tides, tides and sea-level rise, and mixing in the Arctic.
Year(s) Of Engagement Activity 2018
 
Description AGU Ocean Sciences 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Science conference presentations, including convening sessions

collaborations spawned; exchange of information
Year(s) Of Engagement Activity 2010,2012,2014
 
Description SOS Sea food festival 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact my display introduced the public to the concept of tides and how they help control climate, including discussions about the subject.

None yet.
Year(s) Of Engagement Activity 2014