6 research outputs found
Testing the reconstruction of modelled particulate organic carbon from surface ecosystem components using PlankTOM12 and machine learning
Understanding the relationship between surface marine ecosystems
and the export of carbon to depth by sinking organic particles is key to
representing the effect of ecosystem dynamics and diversity, and their
evolution under multiple stressors, on the carbon cycle and climate in
models. Recent observational technologies have greatly increased the amount
of data available, both for the abundance of diverse plankton groups and for
the concentration and properties of particulate organic carbon in the ocean
interior. Here we use synthetic model data to test the potential of using
machine learning (ML) to reproduce concentrations of particulate organic
carbon within the ocean interior based on surface ecosystem and
environmental data. We test two machine learning methods that differ in
their approaches to data-fitting, the random forest and XGBoost methods. The
synthetic data are sampled from the PlankTOM12 global biogeochemical model
using the time and coordinates of existing observations. We test 27
different combinations of possible drivers to reconstruct small (POCS)
and large (POCL) particulate organic carbon concentrations. We show
that ML can successfully be used to reproduce modelled particulate organic
carbon over most of the ocean based on ecosystem and modelled environmental
drivers. XGBoost showed better results compared to random forest thanks to
its gradient boosting trees' architecture. The inclusion of plankton
functional types (PFTs) in driver sets improved the accuracy of the model
reconstruction by 58 % on average for POCS and by 22 % for
POCL. Results were less robust over the equatorial Pacific and some
parts of the high latitudes. For POCS reconstruction, the most
important drivers were the depth level, temperature, microzooplankton and
PO4, while for POCL it was the depth level, temperature,
mixed-layer depth, microzooplankton, phaeocystis, PO4 and chlorophyll a averaged over the mixed-layer depth. These results suggest that it will be
possible to identify linkages between surface environmental and ecosystem
structure and particulate organic carbon distribution within the ocean
interior using real observations and to use this knowledge to improve both
our understanding of ecosystem dynamics and of their functional
representation within models.</p
Copernicus Marine Service ocean state report, issue 4
This is the final version. Available from Taylor & Francis via the DOI in this record. FCT/MCTE
Climate change projections using the IPSL-CM5 Earth System Model: from CMIP3 to CMIP5
We present the global general circulation model IPSL-CM5 developed to study the long-term response of the climate system to natural and anthropogenic forcings as part of the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). This model includes an interactive carbon cycle, a representation of tropospheric and stratospheric chemistry, and a comprehensive representation of aerosols. As it represents the principal dynamical, physical, and bio-geochemical processes relevant to the climate system, it may be referred to as an Earth System Model. However, the IPSL-CM5 model may be used in a multitude of configurations associated with different boundary conditions and with a range of complexities in terms of processes and interactions. This paper presents an overview of the different model components and explains how they were coupled and used to simulate historical climate changes over the past 150 years and different scenarios of future climate change. A single version of the IPSL-CM5 model (IPSL-CM5A-LR) was used to provide climate projections associated with different socio-economic scenarios, including the different Representative Concentration Pathways considered by CMIP5 and several scenarios from the Special Report on Emission Scenarios considered by CMIP3. Results suggest that the magnitude of global warming projections primarily depends on the socio-economic scenario considered, that there is potential for an aggressive mitigation policy to limit global warming to about two degrees, and that the behavior of some components of the climate system such as the Arctic sea ice and the Atlantic Meridional Overturning Circulation may change drastically by the end of the twenty-first century in the case of a no climate policy scenario. Although the magnitude of regional temperature and precipitation changes depends fairly linearly on the magnitude of the projected global warming (and thus on the scenario considered), the geographical pattern of these changes is strikingly similar for the different scenarios. The representation of atmospheric physical processes in the model is shown to strongly influence the simulated climate variability and both the magnitude and pattern of the projected climate changes
Revised estimates of ocean-atmosphere CO2 flux are consistent with ocean carbon inventory
Copernicus Marine Service Ocean State Report, Issue 4
The development of the annual Copernicus Marine Service (CMEMS) Ocean State Report is one of the priority tasks given by the EU Delegation Agreement for the CMEMS implementation (CMEMS ). The Ocean State Report activity was launched with the publication of the first OSR (von Schuckmann et al. ), together with a summary for policy makers (see https://marine.copernicus.eu/science-learning/ocean-state-report/). Currently, the Ocean State Report activity is in its fourth cycle of reporting of the state, variability and change in the marine environment