A thermocline nutrient pump

Lead Research Organisation: Bangor University
Department Name: Sch of Ocean Sciences


The seasonal thermocline in temperate shelf seas acts as a critical interface in the shelf sea system. It is a physical barrier to vertical exchange, controlling biological growth through the summer and enabling the sequestration of atmospheric CO2. Once the spring bloom is over the seasonal thermocline separates the sun drenched but nutrient deplete surface waters from the dark nutrient rich deep water. The vertical mixing of nutrients across the seasonal thermocline acts to couple this well-lit surface zone with the deep water nutrient supply, leading to the formation of a layer of phytoplankton within the thermocline (the subsurface chlorophyll maxima). This phenomenon is estimated to account for about half of the annual carbon fixation in seasonally stratified shelf seas, and yet the controlling physics is only just being unravelled. The identification and parameterisation of the physical processes which are responsible for the vertical mixing of nutrients across the thermocline is a vital prerequisite to our understanding of shelf sea ecosystems. Our proposal is to investigate the role of wind driven inertial oscillations in driving vertical mixing across the seasonal thermocline, identifying the mechanisms and processes responsible for their generation and dissipation on both special and temporal scales. The proposal will be achieved through an observational campaign closely integrated with numerical model predictions using both 1D and 3D numerical models.


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Burchard H (2009) Generation of Bulk Shear Spikes in Shallow Stratified Tidal Seas in Journal of Physical Oceanography

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Charlotte Williams (Author) (2013) Mixing-driven nutrient fluxes and new production in a seasonally stratified shelf sea in Limnology and Oceanography Fluid and Environment

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Hopkins J (2012) On-shelf transport of slope water lenses within the seasonal pycnocline in Geophysical Research Letters

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Liu Z (2010) Instability of Baroclinic Tidal Flow in a Stratified Fjord in Journal of Physical Oceanography

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Palmer M (2013) Variable behavior in pycnocline mixing over shelf seas in Geophysical Research Letters

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Rippeth T (2014) Impact of vertical mixing on sea surface p CO 2 in temperate seasonally stratified shelf seas in Journal of Geophysical Research: Oceans

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Sharples J (2009) Internal tidal mixing as a control on continental margin ecosystems in Geophysical Research Letters

Description A wind driven mechanism - shear spiking - which is responsible for delivery of nutrients to the surface mixed layer of seasonally stratified shelf seas.
Exploitation Route The results of this project inform those running predictive models of shelf sea systems of key processes which must be accurately parameterised.
Sectors Aerospace, Defence and Marine,Environment

Description The results are now used in the design of predictive ocean models
First Year Of Impact 2009
Sector Aerospace, Defence and Marine,Education,Environment
Impact Types Societal

Description NERC Consortium • Carbon and nutrient dynamics and fluxes over shelf systems (Candyflos).
Amount £67,000 (GBP)
Funding ID NE/K001760/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2013 
End 06/2016
Description PCYNMIX (Pcynocline mixing in shelf seas) NERC Standard Grant
Amount £600,000 (GBP)
Funding ID NE/L003600/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2014 
End 09/2017
Description Gangzhou 
Organisation Sun Yat-Sen University
Department Collage of Marine Science
Country Taiwan, Province of China 
Sector Academic/University 
PI Contribution Exploring joint research proposals to extend this field of research
Collaborator Contribution writing proposals
Impact An International Workshop hosted by SYSU
Start Year 2016
Description Visit to Uk Met Office 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact 2 seminars which were followed by discussion specifically focused on understanding which ocean processes need to be included/ better parameterised in weather/ climate forecast models.

further discussion/ collaborations planned.
Year(s) Of Engagement Activity 2014