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Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean-atmosphere water fluxes and oceanic mixing processes

Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean-atmosphere water fluxes and oceanic mixing processes


Title: Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean-atmosphere water fluxes and oceanic mixing processes
Author: Benetti, M.
Reverdin, G.
Aloisi, G.
Sveinbjörnsdóttir, Árný   orcid.org/0000-0002-0310-1283
Date: 2017-06
Language: English
Scope: 4723-4742
University/Institute: Háskóli Íslands
University of Iceland
School: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Department: Jarðvísindastofnun (HÍ)
Institute of Earth Sciences (UI)
Series: Journal of Geophysical Research: Oceans;122(6)
ISSN: 2169-9275
DOI: 10.1002/2017JC012712
Subject: Atlantic; Surface; Hydrology; Mixing; Stable isotope; Salinity; Atlantshaf; Vatnafræði; Sameindir; Sjávarselta
URI: https://hdl.handle.net/20.500.11815/2025

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Citation:

Benetti, M., Lacour, J.‐L., Sveinbjörnsdóttir, A. E., Aloisi, G., Reverdin, G., Risi, C., et al. (2018). A framework to study mixing processes in the marine boundary layer using water vapor isotope measurements. Geophysical Research Letters, 45, 2524– 2532. https://doi.org/10.1002/2018GL077167

Abstract:

The surface ocean hydrological cycle is explored based on ∼300 new δ18O and δD measurements from surface waters of the Atlantic Ocean and the Mediterranean Sea over the period 2010–2016. Our approach combines these surface observations with salinity (S) and stable isotope measurements of atmospheric water vapor. The distinct regional S‐δ distributions are used to identify different surface water masses and their horizontal advection. Moreover, based on assumptions on the δ‐S characteristics of seawater sources and the isotope composition of the evaporative (δe) and meteoric water (δMW) fluxes, the δ‐S distribution is used to indicate the relative importance of evaporation (E) and meteoric water inputs (MW). Here δe is estimated from the Craig and Gordon's equation using 120 days of measurements of the ambient air above the Atlantic Ocean collected during three cruises. To provide quantitative estimates of the E:MW ratio, we use the box model from Craig and Gordon (1965). This identifies the subtropical gyre as a region where E:MW ∼2 and the tropical ocean as a region were MW:E ∼2. Finally, we show that the δ18O‐δD distribution is better represented by a linear fit than the δ‐S relationship, even in basins governed by different hydrological processes. We interpret the δ18O‐δD distribution considering the kinetic fractionation processes associated with evaporation. In the tropical region where MW exceeds E, the δ18O‐δD distribution identifies the MW inputs from their kinetic signature, whereas in regions where E exceeds MW, the δ18O‐δD distribution traces the humidity at the sea surface.

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