Transient tracer-based Investigation of Circulation and Thermal Ocean Change (TICTOC)
Lead Research Organisation:
University of Oxford
Department Name: Oxford Physics
Abstract
Carbon dioxide produced by burning fossil fuels such as oil and gas is building up in the atmosphere and causing the planet to warm. The oceans have absorbed more than 90% of the heat trapped on the planet to date. However, this heating also causes the ocean to expand, leading to rising sea level and consequently to an increased risk to and vulnerability of people and industries located near the coast. Understanding how much sea level will change into the future allows us to plan accordingly the defences we need to install in order to safeguard the infrastructure and livelihoods of our coastal communities.
Warming of the ocean is not geographically uniform however, as ocean currents move heat around the globe. This leads to contrasting changes in ocean temperature and sea level (affecting coastal communities and assets). By the end of the century, some regions may experience very large sea level rises of up to a metre while others will see far less (or even a lowering).
This science program will use observations made from research ships and computer models of the ocean to understand where the ocean takes up heat from the atmosphere and how ocean currents transport and redistribute that heat. To study ocean currents we need a 'tracer' - something that is placed in and moves with the flow, like a chemical dye. Although not intentionally for this purpose, three varieties of tracers have been added to the atmosphere since the 1950s and have since gradually been absorbed into the ocean, and redistributed by ocean currents. These are radioactive carbon (produced by mid 20th century nuclear bomb tests), chlorofluorocarbons (historically used in refrigerators and aerosol cans, and which caused an expansion of the Ozone Hole) and more recently sulphur-hexafluoride (formerly found in tennis balls but now predominantly used in electrical industries as an insulator). These tracers have entered the ocean as distinct pulses at different times, forming a fortuitous experiment we can now observe. We will use high-precision equipment to measure these tracers in the Atlantic and Southern Oceans and collaborate with international partners to track their global fate. We will use these observations to estimate the rate at which heat is being absorbed and re-distributed throughout the ocean and to assess and improve climate model predictions of regional sea level rise.
Warming of the ocean is not geographically uniform however, as ocean currents move heat around the globe. This leads to contrasting changes in ocean temperature and sea level (affecting coastal communities and assets). By the end of the century, some regions may experience very large sea level rises of up to a metre while others will see far less (or even a lowering).
This science program will use observations made from research ships and computer models of the ocean to understand where the ocean takes up heat from the atmosphere and how ocean currents transport and redistribute that heat. To study ocean currents we need a 'tracer' - something that is placed in and moves with the flow, like a chemical dye. Although not intentionally for this purpose, three varieties of tracers have been added to the atmosphere since the 1950s and have since gradually been absorbed into the ocean, and redistributed by ocean currents. These are radioactive carbon (produced by mid 20th century nuclear bomb tests), chlorofluorocarbons (historically used in refrigerators and aerosol cans, and which caused an expansion of the Ozone Hole) and more recently sulphur-hexafluoride (formerly found in tennis balls but now predominantly used in electrical industries as an insulator). These tracers have entered the ocean as distinct pulses at different times, forming a fortuitous experiment we can now observe. We will use high-precision equipment to measure these tracers in the Atlantic and Southern Oceans and collaborate with international partners to track their global fate. We will use these observations to estimate the rate at which heat is being absorbed and re-distributed throughout the ocean and to assess and improve climate model predictions of regional sea level rise.
Planned Impact
TICTOC will ultimately result in improved regional sea level prediction. This will enable society to decide how and where to prioritise spending on mitigating the effects of sea level rise e.g. by installing flood defences. For this to occur, the results of TICTOC need to be rapidly communicated to the key decision making bodies. Many of these ultimately ground their decisions in the assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Hence the IPCC is a key route to Impact for TICTOC. TICTOC will influence the IPCC assessment in two ways:
- By producing policy-relevant knowledge about ocean heat uptake and sea level rise, based on observations and on the CMIP6 models, which will provide the basis for projections in the Sixth Assessment Report (due 2021). To be considered in this report, results will need to be published in the peer-reviewed scientific literature by the likely 2020 deadline, based on the previous timeline. TICTOC investigators from each institute have a track-record of producing papers that are cited in IPCC reports. In addition, investigator Gregory was a coordinating lead author of the sea-level chapter of the IPCC Third Assessment Report (2001), a lead author of the ocean observations and projections chapters of the Fourth (2007), and a lead author of the sea-level chapter of the Fifth (2013), in each case with responsibility for sea-level projections.
- By providing new diagnostics and constraints to inform and improve the next generation of ocean and coupled climate models, which will be used to make improved projections during the 2020s. This will be delivered through the evaluation of OMIP (Ocean Model Intercomparison Project, TICTOC investigator Nurser is part of the co-ordination panel), and FAFMIP (Flux Anomaly Forced Model Intercomparison Project, TICTOC investigator Gregory is part of the co-ordination panel) model runs, both components of the CMIP6 model intercomparison. TICTOC investigators at the NOC are part of the team that provide the ocean model for inclusion in the UK coupled climate modelling contribution by the UK Met Office (TICTOC project partners).
In addition, nationally, TICTOC will influence UK non-government and government stakeholders with whom the Met Office engages including providing sea level projections. The stakeholders include energy companies, infrastructure management, flood risk assessment (EA), UK consultancies, academic institutes etc. The main government stakeholders are BEIS (which includes the function of what was DECC), DEFRA and EA. The PI, McDonagh, will, with project partner Palmer at the Met Office, use the results from TICTOC, particularly the improved sea level predictions, to advise these stakeholders. The main route for this advice will be through UK climate projections (UKCP). The last UKCP was done in 2009 (UKCP09), with the next one due in March 2018 (UKCP18). The results from TICTOC will feed into the subsequent round of UKCP or possibly as an update to UKCP18 if a clear impact can be demonstrated.
TICTOC will expedite communication to the academic community throughout the project, as well as through the usual conferences, seminars and meetings, by interacting with the Programme Advisory Board and inviting key academics to the Royal Society Event that we plan for end of the project in 2021. We will further engage stakeholders by inviting them to this event as well.
- By producing policy-relevant knowledge about ocean heat uptake and sea level rise, based on observations and on the CMIP6 models, which will provide the basis for projections in the Sixth Assessment Report (due 2021). To be considered in this report, results will need to be published in the peer-reviewed scientific literature by the likely 2020 deadline, based on the previous timeline. TICTOC investigators from each institute have a track-record of producing papers that are cited in IPCC reports. In addition, investigator Gregory was a coordinating lead author of the sea-level chapter of the IPCC Third Assessment Report (2001), a lead author of the ocean observations and projections chapters of the Fourth (2007), and a lead author of the sea-level chapter of the Fifth (2013), in each case with responsibility for sea-level projections.
- By providing new diagnostics and constraints to inform and improve the next generation of ocean and coupled climate models, which will be used to make improved projections during the 2020s. This will be delivered through the evaluation of OMIP (Ocean Model Intercomparison Project, TICTOC investigator Nurser is part of the co-ordination panel), and FAFMIP (Flux Anomaly Forced Model Intercomparison Project, TICTOC investigator Gregory is part of the co-ordination panel) model runs, both components of the CMIP6 model intercomparison. TICTOC investigators at the NOC are part of the team that provide the ocean model for inclusion in the UK coupled climate modelling contribution by the UK Met Office (TICTOC project partners).
In addition, nationally, TICTOC will influence UK non-government and government stakeholders with whom the Met Office engages including providing sea level projections. The stakeholders include energy companies, infrastructure management, flood risk assessment (EA), UK consultancies, academic institutes etc. The main government stakeholders are BEIS (which includes the function of what was DECC), DEFRA and EA. The PI, McDonagh, will, with project partner Palmer at the Met Office, use the results from TICTOC, particularly the improved sea level predictions, to advise these stakeholders. The main route for this advice will be through UK climate projections (UKCP). The last UKCP was done in 2009 (UKCP09), with the next one due in March 2018 (UKCP18). The results from TICTOC will feed into the subsequent round of UKCP or possibly as an update to UKCP18 if a clear impact can be demonstrated.
TICTOC will expedite communication to the academic community throughout the project, as well as through the usual conferences, seminars and meetings, by interacting with the Programme Advisory Board and inviting key academics to the Royal Society Event that we plan for end of the project in 2021. We will further engage stakeholders by inviting them to this event as well.
Organisations
Publications
Carson M
(2019)
Climate Model Uncertainty and Trend Detection in Regional Sea Level Projections: A Review
in Surveys in Geophysics
Couldrey M
(2022)
Greenhouse-gas forced changes in the Atlantic meridional overturning circulation and related worldwide sea-level change
in Climate Dynamics
Graven H
(2021)
Future Changes in d 13 C of Dissolved Inorganic Carbon in the Ocean
in Earth's Future
Khatiwala S
(2023)
Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models
in Journal of Advances in Modeling Earth Systems
Khatiwala S
(2022)
Fast spin-up of geochemical tracers in ocean circulation and climate models
Khatiwala S
(2022)
Fast spin-up of geochemical tracers in ocean circulation and climate models
Khatiwala S
(2023)
Fast spin-up of geochemical tracers in ocean circulation and climate models
Kostov Y
(2022)
Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning
in Climate Dynamics
Description | We have reconstructed ocean heat content from 1871 to present. We find an uptake of 436 Zeta Joules of heat over the historical period. |
Exploitation Route | Anyone can now investigate ocean warming going back in time and understand how patterns of warming have changed. |
Sectors | Education Energy Environment |
URL | https://laurezanna.github.io/post/jan_2_2019/ |
Title | Changes in oceanic radiocarbon and CFCs since the 1990s |
Description | This directory contains the MITgcm ECCOv4-TM simulation output used in "Changes in oceanic radiocarbon and CFCs since the 1990s" (Lester et al., 2023) submitted to the Journal of Geophysical Research: Oceans. Ocean tracer simulations were created using transports matrices (TMs) derived from state estimates from the Estimating the Climate and Circulation of the Ocean version 4 (ECCOv4) based on a global configuration of the MITgcm model (MITgcm ECCOv4-TM). The monthly-mean TMs and the transport matrix method was used to simulate CFC-11, CFC-12 and abiotic DIC and 14C in DIC. CFC concentrations were converted to partial pressures (pCFC) by dividing by their solubility functions. Output is provided as Matlab .mat files. Files are named as MITgcm_ECCOv4TM_XXX.mat, where XXX is one of D14C, DIC14, DIC, pCFC11 and pCFC12 and contains annual mean fields for: Delta-14C [per mil], DIC14 concentration [mol/m3], DIC concentration [mol/m3], pCFC-11 concentration [ppt] and pCFC-12 concentration [ppt] respectively. For full details about the simulations and results see Lester et al. (2023). |
Type Of Material | Database/Collection of data |
Year Produced | 2023 |
Provided To Others? | Yes |
URL | https://zenodo.org/record/8242143 |