The University of Southampton
University of Southampton Institutional Repository

Analysis of global surface ocean alkalinity to determine controlling processes

Analysis of global surface ocean alkalinity to determine controlling processes
Analysis of global surface ocean alkalinity to determine controlling processes
The export of calcium carbonate (CaCO3) from the surface ocean is poorly constrained. A better understanding of the magnitude and spatial distribution of this flux would improve our knowledge of the ocean carbon cycle and marine biogeochemistry. Here, we investigate controls over the spatial distribution of total alkalinity in the surface global ocean and produce a tracer for CaCO3 cycling. We took surface ocean bottle data for total alkalinity from global databases (GLODAP, CARINA, PACIFICA) and subtracted the effects of several processes: evaporation and precipitation, river discharge, and nutrient uptake and remineralization. The remaining variation in alkalinity exhibits a robust and coherent pattern including features of large amplitude and spatial extent. Most notably, the residual variation in alkalinity is more or less constant across low latitudes of the global ocean but shows a strong polewards increase. There are differences of ~ 110 ?mol kg- 1 and ~ 85 ?mol kg- 1 between low latitudes and the Southern Ocean and the subarctic North Pacific, respectively, but, in contrast, little increase in the high-latitude North Atlantic. This global pattern is most likely due to production and export of CaCO3 and to physical resupply of alkalinity from deep waters. The use of river corrections highlights the large errors that are produced, particularly in the Bay of Bengal and the North Atlantic, if alkalinity normalization assumes all low salinities to be caused by rainfall. The residual alkalinity data can be used as a tracer to indicate where in the world’s ocean most CaCO3 export from the surface layer takes place, and of future changes in calcification, for instance due to ocean acidification.
alkalinity, calcium carbonates, biogeochemical cycles, tracers
0304-4203
46-57
Fry, Claudia H.
de1cf1f5-9ae2-4fa6-b5ce-9a87fc894a17
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hain, Mathis P.
d31486bc-c473-4c34-a814-c0834640876c
Bates, Nicholas R.
954a83d6-8424-49e9-8acd-e606221c9c57
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Fry, Claudia H.
de1cf1f5-9ae2-4fa6-b5ce-9a87fc894a17
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hain, Mathis P.
d31486bc-c473-4c34-a814-c0834640876c
Bates, Nicholas R.
954a83d6-8424-49e9-8acd-e606221c9c57
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Fry, Claudia H., Tyrrell, Toby, Hain, Mathis P., Bates, Nicholas R. and Achterberg, Eric P. (2015) Analysis of global surface ocean alkalinity to determine controlling processes. Marine Chemistry, 174, 46-57. (doi:10.1016/j.marchem.2015.05.003).

Record type: Article

Abstract

The export of calcium carbonate (CaCO3) from the surface ocean is poorly constrained. A better understanding of the magnitude and spatial distribution of this flux would improve our knowledge of the ocean carbon cycle and marine biogeochemistry. Here, we investigate controls over the spatial distribution of total alkalinity in the surface global ocean and produce a tracer for CaCO3 cycling. We took surface ocean bottle data for total alkalinity from global databases (GLODAP, CARINA, PACIFICA) and subtracted the effects of several processes: evaporation and precipitation, river discharge, and nutrient uptake and remineralization. The remaining variation in alkalinity exhibits a robust and coherent pattern including features of large amplitude and spatial extent. Most notably, the residual variation in alkalinity is more or less constant across low latitudes of the global ocean but shows a strong polewards increase. There are differences of ~ 110 ?mol kg- 1 and ~ 85 ?mol kg- 1 between low latitudes and the Southern Ocean and the subarctic North Pacific, respectively, but, in contrast, little increase in the high-latitude North Atlantic. This global pattern is most likely due to production and export of CaCO3 and to physical resupply of alkalinity from deep waters. The use of river corrections highlights the large errors that are produced, particularly in the Bay of Bengal and the North Atlantic, if alkalinity normalization assumes all low salinities to be caused by rainfall. The residual alkalinity data can be used as a tracer to indicate where in the world’s ocean most CaCO3 export from the surface layer takes place, and of future changes in calcification, for instance due to ocean acidification.

Text
Fry_Analysis.pdf - Accepted Manuscript
Download (1MB)

More information

e-pub ahead of print date: May 2015
Published date: 20 August 2015
Keywords: alkalinity, calcium carbonates, biogeochemical cycles, tracers
Organisations: Ocean and Earth Science, Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 377068
URI: http://eprints.soton.ac.uk/id/eprint/377068
ISSN: 0304-4203
PURE UUID: 06d4cfb0-0c6c-4104-8a0b-2d463e6be8cd
ORCID for Toby Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716

Catalogue record

Date deposited: 14 May 2015 12:26
Last modified: 15 Mar 2024 02:52

Export record

Altmetrics

Contributors

Author: Claudia H. Fry
Author: Toby Tyrrell ORCID iD
Author: Mathis P. Hain

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×