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Variability of alkalinity and the alkalinity-salinity relationship in the tropical and subtropical surface ocean

Variability of alkalinity and the alkalinity-salinity relationship in the tropical and subtropical surface ocean
Variability of alkalinity and the alkalinity-salinity relationship in the tropical and subtropical surface ocean
The variability of total alkalinity (TA) and its relationship with salinity in the tropical and subtropical surface ocean were examined using data collected in various marine environments from a ship of opportunity. In the open ocean regions of the Atlantic, Pacific, and Indian Oceans, sea surface TA variability was observed to be mainly controlled by the simple dilution or concentration (SDC) effect of precipitation and evaporation, and the measured concentrations of TA agreed well with those predicted from salinity and temperature. Non-SDC changes in alkalinity in ocean margins and inland seas were examined by comparing the salinity-normalized alkalinity with that of the open ocean end-member. Non-SDC alkalinity additions to the western North Atlantic margin, eastern North Pacific margin, and Mediterranean Sea were identified, which mainly resulted from river inputs and shelf currents. In contrast, removal of TA through formation and sedimentation of calcium carbonate was observed to be an important control in the Red Sea. The concentration of the river end-member can only be reliably derived from the y intercept of TA-S regression (TAS0) in river-dominated systems such as estuaries and river plumes. In coastal regions where other processes (evaporation, shelf currents, upwelling, calcification, etc.) are more influential, TAS0 can significantly deviate from the river water concentration and hence be an unreliable indicator of it. Negative values of TAS0 can result from non-SDC TA removal at the low salinity end (relative to the salinity of the oceanic end-member) and/or non-SDC TA addition at high salinities (as occurs in the Mediterranean Sea).
alkalinity, salinity, surface ocean, salinity normalization, coastal, river input
0886-6236
729-742
Jiang, Zong-Pei
801435b8-c2e5-476e-84c0-b49ef65ad382
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Dai, Minhan
45b39f60-fc8a-47cf-9318-258374f389fc
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Jiang, Zong-Pei
801435b8-c2e5-476e-84c0-b49ef65ad382
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Dai, Minhan
45b39f60-fc8a-47cf-9318-258374f389fc
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481

Jiang, Zong-Pei, Tyrrell, Toby, Hydes, David J., Dai, Minhan and Hartman, Susan E. (2014) Variability of alkalinity and the alkalinity-salinity relationship in the tropical and subtropical surface ocean. Global Biogeochemical Cycles, 28 (7), 729-742. (doi:10.1002/2013GB004678).

Record type: Article

Abstract

The variability of total alkalinity (TA) and its relationship with salinity in the tropical and subtropical surface ocean were examined using data collected in various marine environments from a ship of opportunity. In the open ocean regions of the Atlantic, Pacific, and Indian Oceans, sea surface TA variability was observed to be mainly controlled by the simple dilution or concentration (SDC) effect of precipitation and evaporation, and the measured concentrations of TA agreed well with those predicted from salinity and temperature. Non-SDC changes in alkalinity in ocean margins and inland seas were examined by comparing the salinity-normalized alkalinity with that of the open ocean end-member. Non-SDC alkalinity additions to the western North Atlantic margin, eastern North Pacific margin, and Mediterranean Sea were identified, which mainly resulted from river inputs and shelf currents. In contrast, removal of TA through formation and sedimentation of calcium carbonate was observed to be an important control in the Red Sea. The concentration of the river end-member can only be reliably derived from the y intercept of TA-S regression (TAS0) in river-dominated systems such as estuaries and river plumes. In coastal regions where other processes (evaporation, shelf currents, upwelling, calcification, etc.) are more influential, TAS0 can significantly deviate from the river water concentration and hence be an unreliable indicator of it. Negative values of TAS0 can result from non-SDC TA removal at the low salinity end (relative to the salinity of the oceanic end-member) and/or non-SDC TA addition at high salinities (as occurs in the Mediterranean Sea).

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e-pub ahead of print date: 17 July 2014
Published date: July 2014
Keywords: alkalinity, salinity, surface ocean, salinity normalization, coastal, river input
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 367070
URI: http://eprints.soton.ac.uk/id/eprint/367070
ISSN: 0886-6236
PURE UUID: 8bba8167-f276-40f8-aea6-a10cdc6cb00b
ORCID for Toby Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716

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Date deposited: 21 Jul 2014 12:16
Last modified: 17 Dec 2019 01:58

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