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Regional surface chlorophyll trends and uncertainties in the global ocean

Regional surface chlorophyll trends and uncertainties in the global ocean
Regional surface chlorophyll trends and uncertainties in the global ocean
Changes in marine primary productivity are key to determine how climate change might impact marine ecosystems and fisheries. Satellite ocean color sensors provide coverage of global ocean chlorophyll with a combined record length of ~ 20 years. Coupled physical–biogeochemical models can inform on expected changes and are used here to constrain observational trend estimates and their uncertainty. We produce estimates of ocean surface chlorophyll trends, by using Coupled Model Intercomparison Project (CMIP5) models to form priors as a “first guess”, which are then updated using satellite observations in a Bayesian spatio-temporal model. Regional chlorophyll trends are found to be significantly different from zero in 18/23 regions, in the range ± 1.8% year−1. A global average of these regional trends shows a net positive trend of 0.08 ± 0.35% year−1, highlighting the importance of considering chlorophyll changes at a regional level. We compare these results with estimates obtained with the commonly used “vague” prior, representing no independent knowledge; coupled model priors are shown to slightly reduce trend magnitude and uncertainties in most regions. The statistical model used here provides a robust framework for making best use of all available information and can be applied to improve understanding of global change.
2045-2322
Hammond, Matthew L.
5c6509e8-0e13-4afa-9b8f-b8601462a93b
Beaulieu, Claudie
13ae2c11-ebfe-48d9-bda9-122cd013c021
Henson, Stephanie A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Sahu, Sujit K.
33f1386d-6d73-4b60-a796-d626721f72bf
Hammond, Matthew L.
5c6509e8-0e13-4afa-9b8f-b8601462a93b
Beaulieu, Claudie
13ae2c11-ebfe-48d9-bda9-122cd013c021
Henson, Stephanie A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Sahu, Sujit K.
33f1386d-6d73-4b60-a796-d626721f72bf

Hammond, Matthew L., Beaulieu, Claudie, Henson, Stephanie A. and Sahu, Sujit K. (2020) Regional surface chlorophyll trends and uncertainties in the global ocean. Scientific Reports, 10 (1), [15273]. (doi:10.1038/s41598-020-72073-9).

Record type: Article

Abstract

Changes in marine primary productivity are key to determine how climate change might impact marine ecosystems and fisheries. Satellite ocean color sensors provide coverage of global ocean chlorophyll with a combined record length of ~ 20 years. Coupled physical–biogeochemical models can inform on expected changes and are used here to constrain observational trend estimates and their uncertainty. We produce estimates of ocean surface chlorophyll trends, by using Coupled Model Intercomparison Project (CMIP5) models to form priors as a “first guess”, which are then updated using satellite observations in a Bayesian spatio-temporal model. Regional chlorophyll trends are found to be significantly different from zero in 18/23 regions, in the range ± 1.8% year−1. A global average of these regional trends shows a net positive trend of 0.08 ± 0.35% year−1, highlighting the importance of considering chlorophyll changes at a regional level. We compare these results with estimates obtained with the commonly used “vague” prior, representing no independent knowledge; coupled model priors are shown to slightly reduce trend magnitude and uncertainties in most regions. The statistical model used here provides a robust framework for making best use of all available information and can be applied to improve understanding of global change.

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Accepted/In Press date: 21 August 2020
Published date: 17 September 2020
Additional Information: Funding Information: The authors are grateful to the ESA for providing the OC-CCI dataset, the data can be found at https://www. esa-oceancolour-cci.org/. We acknowledge the World Climate Research Program’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output (listed in Table 1 of this paper). The code is made publicly available at: https ://github.com/oceanstats/Chlorophyll-trends. MLH was partially funded by a University of Southampton Vice Chancellor’s Studentship Award. CB and MLH were partially supported by a Marie Curie FP7-Reintegration-Grants within the 7th European Community Framework (project 631466-TROPHYZ). Support for SAH was received from NERC National Capability programme CLASS (Climate Linked Atlantic Sector Science), Grant number NE/R015953/1. Publisher Copyright: © 2020, The Author(s).

Identifiers

Local EPrints ID: 444456
URI: http://eprints.soton.ac.uk/id/eprint/444456
ISSN: 2045-2322
PURE UUID: 6f3f9ef1-7089-498b-b714-7e017b889fc3
ORCID for Matthew L. Hammond: ORCID iD orcid.org/0000-0002-8918-2351
ORCID for Sujit K. Sahu: ORCID iD orcid.org/0000-0003-2315-3598

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Date deposited: 20 Oct 2020 16:30
Last modified: 22 Oct 2022 01:36

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Author: Matthew L. Hammond ORCID iD
Author: Sujit K. Sahu ORCID iD

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