Atlantic BiogeoChemical fluxes (ABC)

Lead Research Organisation: National Oceanography Centre
Department Name: Science and Technology

Abstract

The North Atlantic Ocean plays a pivotal role in the global carbon cycle, by storing carbon released into the atmosphere when fossil fuels are burned, and by supporting the sinking flux of organic matter. Our understanding of how horizontal oceanic fluxes in the subtropics contribute to these processes is largely based on shipboard expeditions which occur every 5 years at 24N. Sampling at that interval is insufficient to resolve and understand the role that horizontal transfers play in regulating these processes. Detailed time-series of physical properties at 26.5N from moored instruments suggest that variability in these fluxes will be occurring on a range of timescales. Once this variability is measured, it is almost inevitable that we will modify our understanding of the role the North Atlantic subtropical gyre plays in the global carbon cycle. In this proposal we will address these issues by deploying new chemical sensors and samplers across the Atlantic at 26.5N. We will use the data they provide to calculate time-series of fluxes of nutrient and inorganic carbon, including carbon released to the atmosphere by mans activities, across 26.5N. We will adopt a hierarchical approach, successively using existing observations, then new oxygen observations and ultimately direct observations of the carbon and nutrients in order to identify the added value each successive stage of our programme provides. We will interpret our direct flux calculations as contributions to the North Atlantic budget in conjunction with other observations and models, to assess how oceanic fluxes control the strength and variability of the role the North Atlantic plays in the global carbon cycle.

Planned Impact

Atlantic Biogeochemical Cycles (ABC) is an ambitious multi-institute programme addressing the variability in biogeochemical fluxes at 26.5N. ABC uses new measurements, including from biogeochemical sensors added to the 26.5N moored array, extra samples in the Florida Strait, and from new deep and bio-Argo floats. It will focus on a) understanding the variability of the transport, b) understanding what controls it and c) establishing the impact of the variability on the budgets of the subtropical gyre. This extends work undertaken in RAGNARoCC, the ocean component of the NERC Greenhouse Gases programme.

The major beneficiaries of this information will be policy makers. The Climate Change Act mandates the UK to cut its emissions of six greenhouse gases by 80% in order to stabilize atmospheric CO2 levels at 550 ppm by 2050. We suspect strongly that the natural carbon sink in the North Atlantic may be declining; a major goal of this work is to establish whether this is in fact occurring by focussing on variability in the flux of anthropogenic carbon at the Southern Boundary of the North Atlantic Subtropical Gyre. Project outcomes will thus have a direct bearing on efforts to assess the efficacy of the current UK emissions policy, and is therefore of prime interest to two government departments.

Climate change and its impacts on environmental systems is also of considerable interest to the general public, the media, and to educators from primary school to university level. Our observations of where anthropogenic CO2 is presently stored and of how fast it is transported within the oceans are relevant to these issues and we expect widespread interest in our results.

Our plan for ensuring that our results are made available to these beneficiaries, in a form that is suitable for their use is provided in our Pathways to Impact plan.

Publications

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Weijer W (2019) Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis in Journal of Geophysical Research: Oceans

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McCarthy G (2020) Sustainable Observations of the AMOC: Methodology and Technology in Reviews of Geophysics

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Lebehot A (2019) Reconciling Observation and Model Trends in North Atlantic Surface CO 2 in Global Biogeochemical Cycles

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Holliday NP (2018) Subpolar North Atlantic Overturning and Gyre-Scale Circulation in the Summers of 2014 and 2016. in Journal of geophysical research. Oceans

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Frajka-Williams E (2019) Atlantic Meridional Overturning Circulation: Observed Transport and Variability in Frontiers in Marine Science

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Davila X (2022) How Is the Ocean Anthropogenic Carbon Reservoir Filled? in Global Biogeochemical Cycles

Related Projects

Project Reference Relationship Related To Start End Award Value
NE/M005046/1 05/10/2014 31/10/2019 £994,300
NE/M005046/2 Transfer NE/M005046/1 01/11/2019 04/10/2021 £185,531
 
Title Drone footage from RAPID-ABC Fluxes mooring recovery cruise DY129 on RRS Discovery in December 2020 
Description Drone footage from RAPID-ABC Fluxes mooring recovery cruise DY129 on RRS Discovery in December 2020 
Type Of Art Film/Video/Animation 
Year Produced 2020 
Impact Reached a large scientific and non-scientific audience. Initially shared through Twitter 
URL https://twitter.com/i/status/1349490394774568965
 
Title Timelapse of departure from Southampton of RAPID-ABC Fluxes mooring recovery cruise DY129 on RRS Discovery in December 2020 
Description Timelapse of departure from Southampton of RAPID-ABC Fluxes mooring recovery cruise DY129 on RRS Discovery in December 2020 
Type Of Art Film/Video/Animation 
Year Produced 2020 
Impact Reached a large scientific and non-scientific audience. Initially shared through Twitter 
URL https://twitter.com/i/status/1336618909852643329
 
Title Anthropogenic carbon transports at 26N as estimated using the RAPID-MOCHA-WBTS (RAPID-Meridional Overturning Circulation and Heatflux Array-Western Boundary Time Series) array for 2004 to 2012. 
Description Estimates of anthropogenic carbon derived from hydrographic cruise occupations at 24.5N have been combined with volume transport estimates produced by the RAPID-MOCHA-WBTS (RAPID-Meridional Overturning Circulation and Heatflux Array-Western Boundary Time Series) programme at 26N to generate a time series of anthropogenic carbon transports between 2004 and 2012. Anthropogenic carbon is calculated using measurements of temperature, salinity, dissolved inorganic carbon, total alkalinity, oxygen, inorganic nutrients and chlorofluorocarbons collected on cruises between the east coast of USA and Africa between 1992 and 2011. The volume transport time series is derived from measurements of temperature, salinity, pressure and water velocity from an array of moored instruments that extend from the east coast of the Bahamas to the continental shelf off Africa east of the Canary Islands, combined with estimates of the transport in the Florida Strait derived from sub-sea cable measurements calibrated by regular hydrographic cruises, and satellite scatterometer measurements (wind driven Ekman transport). This data release includes published paper with a full description of the calculation of anthropogenic carbon fields and their transports, and references to more detailed description of the volume transport time series calculation. The anthropogenic carbon transports form part of the Atlantic Biogeochemical Fluxes programme (Principle Investigator Elaine McDonagh). 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact Estimates of anthropogenic carbon derived from hydrographic cruise occupations at 24.5N have been combined with volume transport estimates produced by the RAPID-MOCHA-WBTS (RAPID-Meridional Overturning Circulation and Heatflux Array-Western Boundary Time Series) programme at 26N to generate a time series of anthropogenic carbon transports between 2004 and 2012. Used as basis of publication in Nature Geoscience, in press 2021 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/b6bb9f45-f562-68a4-e053-6c86abc...
 
Description Met Office Carbon Cycle 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Academic/University 
PI Contribution Running model simulations
Collaborator Contribution Technical support
Impact No outputs yet
Start Year 2015