Abstract
Abstract. The last few decades have seen dramatic changes in the hydrography and biogeochemistry of the Mediterranean Sea. The complex bathymetry and highly variable spatial and temporal scales of atmospheric forcing, convective and ventilation processes contribute to generate complex and unsteady circulation patterns and significant variability in biogeochemical systems. Part of the variability of this system can be influenced by anthropogenic contributions. Consequently, it is necessary to document details and to understand trends in place to better relate the observed processes and to possibly predict the consequences of these changes. In this context we report data from an oceanographic cruise in the Mediterranean Sea on the German research vessel Maria S. Merian (MSM72) in March 2018. The main objective of the cruise was to contribute to the understanding of long-term changes and trends in physical and biogeochemical parameters, such as the anthropogenic carbon uptake and to further assess the hydrographical situation after the major climatological shifts in the eastern and western part of the basin, known as the Eastern and Western Mediterranean Transients. During the cruise, multidisciplinary measurements were conducted on a predominantly zonal section throughout the Mediterranean Sea, contributing to the Med-SHIP and GO-SHIP long-term repeat cruise section that is conducted at regular intervals in the Mediterranean Sea to observe changes and impacts on physical and biogeochemical variables. The data can be accessed at https://doi.org/10.1594/PANGAEA.905902 (Hainbucher et al., 2019), https://doi.org/10.1594/PANGAEA.913512 (Hainbucher, 2020a) https://doi.org/10.1594/PANGAEA.913608, (Hainbucher, 2020b) https://doi.org/10.1594/PANGAEA.913505, (Hainbucher, 2020c) https://doi.org/10.1594/PANGAEA.905887 (Tanhua et al., 2019) and https://doi.org/10.25921/z7en-hn85 (Tanhua et al, 2020).
Highlights
Contrary to earlier ideas that the Mediterranean Sea is always in a steady state, we know in the light of new research that the Mediterranean Sea is not, and it is potentially sensitive to climatic changes (Malanotte-Rizzoli, 2014)
Underway (UW) measurements of partial pressure of CO2, and dissolved oxygen partial pressure in seawater were carried out by means of a Contros HydroC pCO2 analyzer for pCO2 and an Aanderaa optode for oxygen
Discrete CO2 variables were measured on board, i.e., dissolved inorganic carbon (DIC), pH, total alkalinity (TA) and carbonate ion (CO23−); these variables were measured at selected stations and depths (Table 9)
Summary
Contrary to earlier ideas that the Mediterranean Sea is always in a steady state, we know in the light of new research that the Mediterranean Sea is not, and it is potentially sensitive to climatic changes (Malanotte-Rizzoli, 2014). Strong deep convection induced by extreme atmospheric events during winter in 2004–2006 (low precipitation, cold, persistent winds) enhanced salt and temperature in the entire basin up to about 1600 m (Schroeder et al, 2006, 2008) This abrupt climate shift is referred to as Western Mediterranean Transient (WMT) and the physical changes are comparable to the EMT, both in terms of intensity and observed effects (Schroeder et al, 2008). Most of DOC is produced in situ, external sources (atmosphere, rivers, sediments) may affect its concentration and distribution Physical processes, such as deep-water formation, thermohaline circulation, vertical stratification and mesoscale activities have been reported to be the main drivers of DOC distribution in the Mediterranean Sea (Santinelli, 2015; Santinelli et al, 2015, 2013).
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