monitoring the atlantic overturning circulation

Research Objectives

The RAPID AMOC programme is designed to encourage novel uses of data from the 26°N RAPID array. The three main research objectives are:

  1. Novel approaches to ocean state estimation using 26.5°N data.
  2. The role of the AMOC in climate variability and predictability.
  3. Biogeochemical fluxes.

Three projects have been funded to address these objectives, starting in late autumn 2014. The projects are:

  1. Reanalysis of the AMOC. Abstract
  2. DYNamics and predictability of the Atlantic Meridional Overturning and Climate (DYNAMOC). Abstract
  3. Atlantic BiogeoChemical fluxes (ABC) Abstract

Scientific research

Research activities in the RAPID-AMOC programme focus on using data from the RAPID array at 26°N with other observations and numerical models to increase our understanding of processes that control variability and change in the Atlantic meridional overturning circulation (AMOC), and how AMOC observations at 26°N can improve our ability to predict future climate variability and change.

Research in RAPID-AMOC is carried out in close collaboration with other international programmes that also study the AMOC, in particular the OSNAP and US-AMOC programmes.

Reanalysis of the AMOC

The Atlantic Meridional Overturning Circulation (AMOC for short) transports warm and saline Atlantic surface waters northward to high polar latitudes where it is transformed into colder (and also fresher) water, which sinks and returns southward underneath the warm waters. The Gulf stream is the best known surface current that contributes to carrying the warm surface waters to the north. The strength of this exchange flow has been monitored now for 10 years at Latitude 26N (Florida-Africa).

Models suggest that low frequency changes in this AMOC flow may (i) be predictable some years ahead, and (ii) lead to changes in North Atlantic weather and climate some years later due to changing the warm water distribution at the ocean surface.

To realise the potential of the AMOC monitoring measurements at 26N these observations need to be successfully "assimilated" into the ocean and climate prediction models being currently used at the Met Office and elsewhere.

This project will develop novel methods to introduce the AMOC observational data into the latest ocean and climate model environments, in combination with other complementary datasets that are available, e.g. from ocean profiling floats (ARGO), and from satellites measuring sea surface temperatures and sea level.

The experiments will be carried out in close collaboration with scientists from the Met Office and the European Centre for Medium Range Weather Forecasts (ECMWF) in order to allow rapid take up of successful innovations.

DYNamics and predictability of the Atlantic Meridional Overturning and Climate (DYNAMOC)

The 'Atlantic Meridional Overturning Circulation', or AMOC, describes a large scale circulation of the North Atlantic Ocean which carries warm surface waters northward and cooler deeper waters southwards. This circulation carries huge amounts of heat, and variations in its strength can have a substantial influence on European climate.

The DYNAMOC project aims to improve understanding of how this circulation has varied in the past and how it has affected climate, and also to assess the potential for useful predictions months to years ahead.

DYNAMOC will make use of new advanced computer simulations and forecasting systems which are able to simulate the AMOC in unprecedented detail. It will also make use of the RAPID observations of the AMOC strength at 26 degrees North, available since 2004, as a benchmark for testing the models and predictions. The research will test some specific hypotheses about how the AMOC works, how it is changing now. It will investigate how a slow down or speed up in the AMOC affects summers and winters in the UK and other countries.

DYNAMOC will provide an assessment of the likely behaviour of the AMOC, and its impacts on climate, over the next decade. It will also produce recommendations for improving forecasting systems in the future.

DYNAMOC is a collaboration between the National Centre for Atmospheric Science at the University of Reading, the National Oceanography Centre and the UK Met Office.

Atlantic BiogeoChemical fluxes (ABC)

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.

ABC is a collaboration between the National Oceanography Centre (NOC), University of Exeter's Department of Geography, University of Southampton's School of Ocean and Earth Science, and Plymouth Marine Laboratory (PML).