The North Atlantic Climate System Integrated Study

Lead Research Organisation: NERC British Antarctic Survey
Department Name: Science Programmes


Major changes are occurring across the North Atlantic climate system: in ocean and atmosphere temperatures and circulation, in sea ice thickness and extent, and in key atmospheric constituents such as ozone, methane and particles known as aerosols. Many observed changes are unprecedented in instrumental records. Changes in the North Atlantic directly affect the UK's climate, weather and air quality, with major economic impacts on agriculture, fisheries, water, energy, transport and health. The North Atlantic also has global importance, since changes here drive changes in climate, hazardous weather and air quality further afield, such as in North America, Africa and Asia.

ACSIS is a 5 year strategic research programme that brings together and exploits a wide range of capabilities and expertise in the UK environmental science community. It's goal is to enhance the UK's capability to detect, attribute (i.e. explain the causes of) and predict changes in the North Atlantic Climate System. ACSIS will deliver new understanding of the NA climate system by integrating new and old observations of atmospheric physics and chemistry, of the ocean state and of Arctic Ice. The observations will be complemented by detailed data analysis and numerical simulations.

Observations will come from existing networks, from NERC's own observational sites in the North Atlantic, and from space. Seasonal surveys using the NCAS FAAM aeroplane will further enhance our observational strategy. A key dimension of the observational opportunity is that data records of sufficient length, for multiple variables, are becoming available for the first time. The modelling component will involve core numerical simulations with cutting-edge atmosphere, ocean, sea ice, chemistry and aerosol models using the latest parameterizations and unprecedented spatial detail, as well as bespoke experiments to investigate specific time periods or to explore and explain particular observations.

ACSIS will provide advances in understanding and predicting changes in the NA climate system that can be exploited to assess the impact of these changes on the UK and other countries - for example in terms of the consequences for hazardous weather risk, the environment and businesses. ACSIS outputs will also inform policy on climate change adaptation and air quality.

Planned Impact

Policy makers: Advances in understanding the role of natural and anthropogenic drivers in North Atlantic climate change delivered by ACSIS will contribute to the next Intergovernmental Panel on Climate Change Assessment Report (AR6) and to national and international policy-making on climate change adaptation and mitigation. Improved understanding of the impact of stratospheric ozone change on tropospheric composition and climate will inform assessments for the Montreal Protocol. Advances in understanding the role of emissions, relative to other factors, in shaping UK air quality will benefit policy formulation in Defra. Representatives of relevant government departments will be invited to the Community Meetings that are a planned part of the programme. These meetings will include specific sessions on stakeholder needs. The Met Office and its customers will benefit from the process-based evaluation of their models and forecast systems. Improvements in modelling and understanding will be exploited to improve the accuracy and reliability of climate forecasts and projections. This will happen efficiently through the co-delivery of ACSIS by Met Office and NERC scientists. The EU Copernicus Climate Change Service will benefit from advances in observations, models, understanding and predictions of changes in the regional climate of the North Atlantic/European region. ACSIS partners are already directly engaged in the development of relevant services and this engagement will increase through the programme. Businesses concerned with changing weather and weather-related risks will benefit from advances in understanding the drivers of changing risk. ACSIS partners have established collaborations with the insurance and energy industries in particular, and these collaborations will provide an important pathway for communication of ACSIS findings. These interactions will be enhanced internationally through related work in the EU PRIMAVERA programme, as well as through the Community Meetings mentioned above.

General public and the media. The observations of declining Arctic sea-ice have become an iconic symbol of our changing climate system for the media and the general public. The ACSIS Essential Climate Variables, presented in accessible form and updated regularly on the ACSIS website, will provide a similar but broader based snap-shot of how the climate system is changing in the UK's backyard. The presentation of multiple variables in a consistent format will provide an important regular opportunity for ACSIS scientists to discuss and explain the complex nature of changes in a way that is accessible and engaging. We anticipate a high level of media interest in this dimension of the programme.

ACSIS is specifically designed to enable as well as deliver research and as such there is a wide community of academic beneficiaries (see separate summary), who will themselves contribute to enhancing the overall impacts of the programme.


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Description 1) The stratosphere may play an important role in affecting the North Atlantic region during winter season via downward wave reflection.

2) New mechanisms are identified in terms of the solar-induced decadal signal.

3) Examination of the nonlinear processes such as breaking planetary waves, internal reflection, and resonance helps to identify and characterise the stratospheric influences. It also points to directions for studying the model biases.

4) The post-1862 North Atlantic multi-decadal westerly jet strength variability is too weak in CMIP5 and CMIP6, with similar, but less pronounced, discrepancies for NAO variability.

5) ) Evidence suggests that a contributor to this too-weak jet strength variability is too-weak ocean-atmosphere coupling in the northern North Atlantic as a consequence of equatorward winter jet-stream biases in the CMIP models. 6) An observed strong multi-decadal correlation between North Altlantic jet strength and the NAO may be specific to the 1862-2005 period

6) We used adjoint sensitivity fields to quantify possible influences on Labrador Sea heat content. We identified a basin-scale adjustment mechanism involving the West African and European shelves. In addition, we quantified the extent to which non-local heat fluxes can impact Labrador Sea heat content. (Jones et al., 2018)

7) In Dittmar et al. (2017), we argued that there is a conceptual error in a recently published study of dissolved organic sulphur. The authors of the study neglected mixing between water masses, using radiocarbon age as an overly simple proxy for the age of water. We found that mixing between water masses is sufficient to explain the authors' degradation rates, suggesting that the original study cannot distinguish mixing-driven dilution (interpreted as degradation) and biogeochemical degradation of water parcels following adiabatic trajectories.

8) Teleconnections between the Quasi Biennial Oscillation (QBO) and the Northern Hemisphere zonally averaged zonal winds, mean sea level pressure (mslp) and tropical precipitation are examined. The QBO-induced changes near the NA regions are found to be primarily associated with a QBO modulation of the stratospheric polar vortex.

9) The QBO effect on the winter stratospheric polar vortex involves wavenumber-dependent Rossby wave breaking at different time and height. The North Atlantic Oscillation, which strongly affects UK weather, is expected to be more negative in early winter when the QBO is in its easterly phase and also in late winter when the QBO is in its westerly phase. This suggests that the phase of the QBO, which is predictable on long timescales, could be a useful predictor for UK winter weather.

10) Analysis of ECCOv4 heat budgets and adjoint reconstructions show that the recent North Atlantic "cold blob" anomaly (i.e. record low SSTs in 2015) was caused by successive winters with extreme heat loss. It was a largely local response. See

11) We designed and implemented a probabilistic, deep learning sea ice forecasting system called IceNet. This new system outperforms a state-of-the-art dynamical model in seasonal forecasts of summer sea ice. It also demonstrates a greater ability to predict anomalous pan-Arctic sea ice extents than the models submitted to the Sea Ice Outlook programme. The system is described in a paper that is now under review for Nature Communications - preprint available at .
Exploitation Route The adjoint modelling approach used in this project has many other applications to ocean-climate problems. Current efforts include adjoint sensitivity studies of the recent North Atlantic cold anomaly (Josey et al., 2018) and the wider subpolar North Atlantic, specifically the area used to define the Subpolar Ocean Heat Content (SOHC) ACSIS indicator.

In addition, we are applying machine learning techniques to the updated North Atlantic SST dataset that is currently being produced by NOC. This builds on the unsupervised classification results published in Jones et al. (2019).
Sectors Environment

Description The findings have contributed to a number of public engagement activities: - Producer and host (Dan Jones), the Climate Scientists podcast ( - Reviewer for Climate Feedback ( - Extensive social media activity - Public and community engagement events (Avonmouth, UK; Cambridge Science Festival) - School engagement events (University of Cambridge Primary School; St Albans Girls School; St Albans High School for Girls)
First Year Of Impact 2017
Sector Education
Impact Types Societal

Description Media briefing on sea ice 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact In March 2017 Emily Shuckburgh co-ordinated the production of a briefing note on sea ice and participated in a press briefing which focused on the impact of Arctic sea ice loss on midlatitude weather.
Year(s) Of Engagement Activity 2017
Description School visit (St Albans) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Gave a talk including discussion of the ACSIS project to St Albans Girls School
Year(s) Of Engagement Activity 2016
Description Sensing the climate: how do we measure our changing planet? 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Hosted a series of talks, including ACSIS as part of the Cambridge Science Festival
Year(s) Of Engagement Activity 2018