RAGNARoCC: Radiatively active gases from the North Atlantic Region and Climate Change
Lead Research Organisation:
National Oceanography Centre
Department Name: Science and Technology
Abstract
Our object is to understand how large, and how variable, are sources and sinks of greenhouse gases to the atmosphere from the North Atlantic. We aim to be able to describe how these have changed in the recent past and how they will change in the future under different climate scenarios. Most effort will be concentrated on carbon dioxide, and we will deliver a comprehensive budgeting of natural and anthropogenic components of the carbon cycle in the North Atlantic and understanding of why the air-sea fluxes of CO2 vary regionally, seasonally and multi-annually. Observations of CH4 and N2O and estimates of their regional fluxes will additionally be made. We, in collaboration with our partner institutions in Europe and the US, will undertake surface measurements of CO2 air-sea fluxes made from networks of voluntary observing ships and at fixed sites. These will be synthesised with observations from hydrographic sections of the interior carbon content. We will thus obtain accurate estimates of the uptake, present storage, and net transport of anthropogenic carbon, and variability in the natural uptake and release of atmospheric CO2 by the N. Atlantic. In parallel with direct estimates made from these observations, forward and inverse models (of both atmospheric and oceanic kinds) of these fluxes will be developed. The main hypotheses are (1) that past uptake and variability of CO2 in the region can be quantified by examination of the deep carbon inventory in the Atlantic, (2) that the present observed variability in CO2 uptake is due to a combination of biological and physical processes that are driven by climatic variations, the main factors being captured by ocean carbon simulations embedded in climate models, and (3) these variations (past, present and future) are due to a combination of variability internal to the climate system and external anthropogenic forcing - in proportions we will determine. Objectives are (1) a template for operational forecasting of the fluxes of GHGs into and out of the N. Atlantic, to be implemented as part of ICOS and in combination with ECMWF (2) an understanding of that sink that can be used to improve projections of how the ocean CO2 sink will change in the future, and (3) a quantitative understanding of how and why Atlantic Ocean uptake of anthropogenic CO2 has changed as a result of climate change over the last 100 years.
Planned Impact
See Lead proposal
Publications

Brown P
(2021)
Circulation-driven variability of Atlantic anthropogenic carbon transports and uptake
in Nature Geoscience

Bryden H
(2020)
Reduction in Ocean Heat Transport at 26°N since 2008 Cools the Eastern Subpolar Gyre of the North Atlantic Ocean
in Journal of Climate

Bryden H
(2014)
Impact of a 30% reduction in Atlantic meridional overturning during 2009-2010
in Ocean Science

Clarke J
(2017)
Characterization of a Time-Domain Dual Lifetime Referencing pCO2 Optode and Deployment as a High-Resolution Underway Sensor across the High Latitude North Atlantic Ocean
in Frontiers in Marine Science


Couldrey M
(2016)
On which timescales do gas transfer velocities control North Atlantic CO 2 flux variability? CARBON FLUX CONTROLS
in Global Biogeochemical Cycles

Henson S
(2018)
Controls on Open-Ocean North Atlantic ? p CO 2 at Seasonal and Interannual Time Scales Are Different
in Geophysical Research Letters

McCarthy G
(2015)
Continuous Estimate of Atlantic Oceanic Freshwater Flux at 26.5°N
in Journal of Climate

Sonnewald M
(2013)
Atlantic meridional ocean heat transport at 26° N: impact on subtropical ocean heat content variability
in Ocean Science

Talley LD
(2016)
Changes in Ocean Heat, Carbon Content, and Ventilation: A Review of the First Decade of GO-SHIP Global Repeat Hydrography.
in Annual review of marine science