Periodic Reporting for period 5 - GOCART (Gauging Ocean organic Carbon fluxes using Autonomous Robotic Technologies)
Periodo di rendicontazione: 2022-11-01 al 2024-02-29
Climate change driven by CO2 emissions from human activities is a significant challenge facing mankind. An important component of Earth’s carbon (C) cycle is the ocean’s biological C pump; without it atmospheric CO2 would be ~50% higher than it is now. The pump consists of sinking organic matter which is remineralised back into CO2 in the deep ocean. The depth at which remineralisation occurs is the main factor affecting the amount of organic C stored in the ocean. Currently we do not understand how or why remineralisation depth varies in time, which limits our ability to make robust predictions of how the future C cycle, and hence our climate, will change into the future. This is mainly due to the challenges of measuring remineralisation depth using conventional methods– a barrier which autonomous underwater vehicles are poised to overcome by providing high frequency data over long periods. This technological innovation will revolutionise our understanding of this important planetary C flux.
GOCART is an ambitious project to address current uncertainties in remineralisation depth. GOCART encompasses new observations, obtained using cutting-edge technology and novel methodology, through to global climate modelling. Underwater glider deployments will be used to establish the characteristics and significance of temporal variability in organic C flux and remineralisation depth during the most dynamic period of the year. This will enable new insights into the factors driving variability in remineralisation depth, ultimately leading to development of a new model parameterisation incorporating temporal variability. Using an innovative modelling framework, this parameterisation will be tested for its potential to improve predictions of ocean C storage. GOCART represents a significant advance in quantifying temporal variability in remineralisation depth, which is key to reducing uncertainty in model predictions of ocean C storage, and yet currently almost entirely unknown.
GOCART is an ambitious project to address current uncertainties in remineralisation depth. GOCART encompasses new observations, obtained using cutting-edge technology and novel methodology, through to global climate modelling. Underwater glider deployments will be used to establish the characteristics and significance of temporal variability in organic C flux and remineralisation depth during the most dynamic period of the year. This will enable new insights into the factors driving variability in remineralisation depth, ultimately leading to development of a new model parameterisation incorporating temporal variability. Using an innovative modelling framework, this parameterisation will be tested for its potential to improve predictions of ocean C storage. GOCART represents a significant advance in quantifying temporal variability in remineralisation depth, which is key to reducing uncertainty in model predictions of ocean C storage, and yet currently almost entirely unknown.
In the final reporting period, GOCART has finalised all datasets generated during the project and made them publicly available. Multiple papers using these datasets to achieve the project’s objectives have been published or are in the final stages of preparation. The team members have developed their careers through their involvement in GOCART, including now sitting on international committees dedicated to best practices in autonomous biogeochemistry. The GOCART project opened a new field of research internationally, with the use of autonomous vehicles to estimate organic carbon fluxes now becoming more frequent, building on the methods developed during the project. In terms of the new scientific insights gained, we have quantified the seasonal variability in export flux, identified potential biogeochemical and biological processes underlying that variability, explored how episodicity in fluxes can bias estimates derived from traditional shipboard sampling methods, identified how mesoscale variability in physical and biological conditions can alter flux attenuation, assessed the predicted future estimates of organic carbon flux in existing climate models, considered how processes currently missing from those models may affect future projections, introduced seasonal and spatial variability in flux attenuation into a global model and investigated its influence on projections, explored how the spatial bias in shipboard sampling affects global estimates of export flux and how autonomous vehicles may be able to overcome this. In short, we have generated a significant number of outputs which have advanced the community’s ability to obtain robust estimates of organic carbon flux and attenuation from autonomous vehicles, enhanced understanding of the significance of temporal variability in fluxes, and fed our new understanding through into new modelling capabilities. The GOCART project has therefore achieved all of its main objectives.
GOCART undertook the first multi-month glider missions designed to quantify the sub-daily to seasonal variability in particulate organic carbon flux and remineralisation length scale. The semi-automated processing and calibration of the glider data streams has been established in ‘toolbox’ form by GOCART. This substantial piece of work at the start of the project allowed the later glider deployments to be more autonomously processed. The methods we developed have allowed other groups worldwide working with glider data to generate estimates of organic carbon flux.
The dataset collected by GOCART allowed us to establish the characteristics and significance of temporal variability in organic carbon flux and remineralisation depth. GOCART has also generated new insights into the factors driving variability in remineralisation depth, and has resulted in development of a new model parameterisation incorporating temporal variability.
The project has delivered each of the GOCART objectives:
1. Quantify the variability in flux of particulate organic carbon through the TZ and its RLS on daily to sub-seasonal timescales
2. Determine the characteristics and significance of episodic pulses of flux
3. Investigate potential drivers of episodic flux pulses
4. Quantify the effect of temporal variability on uncertainty in RLS estimates
5. Establish and test a new empirical parameterisation of RLS that incorporates temporal variability
The dataset collected by GOCART allowed us to establish the characteristics and significance of temporal variability in organic carbon flux and remineralisation depth. GOCART has also generated new insights into the factors driving variability in remineralisation depth, and has resulted in development of a new model parameterisation incorporating temporal variability.
The project has delivered each of the GOCART objectives:
1. Quantify the variability in flux of particulate organic carbon through the TZ and its RLS on daily to sub-seasonal timescales
2. Determine the characteristics and significance of episodic pulses of flux
3. Investigate potential drivers of episodic flux pulses
4. Quantify the effect of temporal variability on uncertainty in RLS estimates
5. Establish and test a new empirical parameterisation of RLS that incorporates temporal variability