An Initial Assessment of the Contribution of Fresh Submarine Ground Water Discharge to the Alkalinity Budget of the Mediterranean Sea. Issue 8 (6th August 2021)

• Record Type: Journal Article
• Authors: Kolker, D.; Bookman, R.; Herut, B.; David, N.; Silverman, J.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-06
• Subjects: total alkalinity -- FSGD -- Mediterranean Sea -- carbonate system; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2020JC017085
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Excess total alkalinity (TA) of Mediterranean Sea (MS) seawater relative to its Atlantic origin has been attributed to high inputs from major rivers and the Black Sea. Submarine groundwater discharge (SGD), which was recently shown to be an important source of nutrients to the MS, may also be an important source of TA to the MS. During 2015–2017, water samples were taken from a shoreline groundwater spring near Tel‐Shikmona, northern Israel, and analyzed for TA, salinity, and dissolved inorganic nutrients. Spring water TA varied seasonally between a low of 3, 919 and a high of 7, 148 µmol kg −1 in the summer and winter, respectively. Long‐term records from a nearby monitoring site indicate that wintertime coastal water TA is positively correlated with annual rainfall rates. Based on the Tel‐Shikmona groundwater spring measurements and other measurements from the MS region reported in the literature, we estimated that the TA flux from the fresh component of SGD (FSGD) in this region is 22%–37% and 17%–30% of the riverine and Black Sea TA fluxes to the MS, respectively. Plain Language Summary: The oceans have absorbed much of the CO2 emitted to the atmosphere since the beginning of the industrial revolution. The ability of seawater to absorb this excess CO2 in the atmosphere is a strong function of a chemical attribute of seawater called total alkalinity (TA). Where seawater with higher TA is able to absorb more CO2 relative to seawater with lower TA. In this study, we tried to assess the relative contribution of submarine groundwater discharge (SGD) along the land boundaries of the Mediterranean Sea (MS) to its TA budget. During 2015–2017, water samples were taken from a shoreline groundwater spring near Tel‐Shikmona, northern Israel, and analyzed for TA, salinity, dissolved inorganic nutrients and carbon. The results of our measurements together with relevant data from the scientific literature indicate that the TA flux into the MS from SGD is 22%–37% and 17%–30% of the riverine and Black Sea TA fluxes into the MS, respectively. The results of this study suggest that SGD TA flux to the MS and the oceans in general could be an important and previously overlooked feedback mechanism for the anthropogenic increase and glacial/interglacial variations in atmospheric CO2 . Key Points: Surface water excess alkalinity relative to salinity in the Mediterranean Fresh groundwater discharge into the Mediterranean has very high alkalinity that varies seasonally Input of total alkalinity from fresh submarine groundwater discharge is comparable to riverine and Black Sea inputs of alkalinity