The first deep-sea mooring station in the eastern Levantine basin (DeepLev), outline and insights into regional sedimentological processes

Katz, Timor; Weinstein, Yishai; Alkalay, Ronen; Biton, Eli; Toledo, Yaron; Lazar, Ayah; Zlatkin, Olga; Soffer, Rotem; Rahav, Eyal; Sisma-Ventura, Guy; Bar, Tslil; Ozer, Tal; Gildor, Hezi; Almogi‐Labin, Ahuva; Kanari, Mor; Berman‐Frank, Ilana; Herut, Barak

doi:10.1016/j.dsr2.2019.104663

Cited by 31 publications

(41 citation statements)

References 58 publications

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“…Thus, the 2020 mean oxygen concentration in the depth range of 1,200-1,950 m of 179.5 ± 2.3 μmol kg −1 is comparable to the pre-EMT mean value (Klein et al, 2003;Kress et al, 2003). The significant change in deep water DO concentrations can be driven by two main mechanisms: (1) changes in the recycling rates driven by changes in export of labile organic carbon via the biological carbon pump and/or by lateral transport of POM in marginal seas (i.e., Katz et al, 2020) and ( 2) changes in deep water formation and ventilation rates, as well as deep advection and admixture (Keller et al, 2002). Advection of dense Aegean overflow would tend to increase both salinity and oxygen (Kress et al, 2014).…”

Section: Resultsmentioning

confidence: 56%

Post-eastern Mediterranean Transient Oxygen Decline in the Deep Waters of the Southeast Mediterranean Sea Supports Weakening of Ventilation Rates

et al. 2021

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Long-term trends in oxygen, salinity, and nutrients were followed in the Southeastern Mediterranean (SEMS) deep waters from 2002 to 2020. Results show a net decrease in oxygen since 2008 of −0.5 ± 0.1 μmol kg−1 yr−1 in the bathypelagic depths (1,200–2,000 m). Multiannual variability in oxygen levels superimposed this trend, and is likely associated with variations in thermohaline fluxes. The 2020 mean oxygen concentration of 179.5 ± 2.3 μmol kg−1 is comparable to the pre-Eastern Mediterranean Transient (EMT) mean value. The post-EMT signature is clearly demonstrated in both oxygen and salinity over the period of 2002–2013, but since 2014 it diminished, mainly due to mixing of the Aegean deep water (AegDW) mass with the overlying old Adriatic water mass. This trend reflects a switch back to the pre-EMT regime, characterized by thermohaline homogeneity of the deep water column in the SEMS. The long-term decline of deep water oxygen levels is also accompanied by a corresponding increase in dissolved inorganic nutrients, supporting aging of the deep water masses. Our results suggest that ventilation of the SEMS deep water is currently occurring at a lower, pre-EMT rate, probably as a result of moderated deep water formation in recent time.

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Section: Resultsmentioning

confidence: 56%

Post-eastern Mediterranean Transient Oxygen Decline in the Deep Waters of the Southeast Mediterranean Sea Supports Weakening of Ventilation Rates

et al. 2021

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“…However, both of our sampling locations are characterized as oligotrophic seas, with similar chlorophyll A concentrations typically lower than 0.4µg/l. 31,32 Thus our initial assessment for seawater-emitted COS isotopic signal, may not be representative of the global oceans. Based on all of the noted above, we created a measurement-based isotopic mass balance for tropospheric COS (Eq.…”

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confidence: 99%

Tropospheric carbonyl sulfide mass balance based on direct measurements of sulfur isotopes

Davidson

Amrani

Angert

2021

Proc. Natl. Acad. Sci. U.S.A.

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Robust estimates for the rates and trends in terrestrial gross primary production (GPP; plant CO2 uptake) are needed. Carbonyl sulfide (COS) is the major long-lived sulfur-bearing gas in the atmosphere and a promising proxy for GPP. Large uncertainties in estimating the relative magnitude of the COS sources and sinks limit this approach. Sulfur isotope measurements (34S/32S; δ34S) have been suggested as a useful tool to constrain COS sources. Yet such measurements are currently scarce for the atmosphere and absent for the marine source and the plant sink, which are two main fluxes. Here we present sulfur isotopes measurements of marine and atmospheric COS, and of plant-uptake fractionation experiments. These measurements resulted in a complete data-based tropospheric COS isotopic mass balance, which allows improved partition of the sources. We found an isotopic (δ34S ± SE) value of 13.9 ± 0.1‰ for the troposphere, with an isotopic seasonal cycle driven by plant uptake. This seasonality agrees with a fractionation of −1.9 ± 0.3‰ which we measured in plant-chamber experiments. Air samples with strong anthropogenic influence indicated an anthropogenic COS isotopic value of 8 ± 1‰. Samples of seawater-equilibrated-air indicate that the marine COS source has an isotopic value of 14.7 ± 1‰. Using our data-based mass balance, we constrained the relative contribution of the two main tropospheric COS sources resulting in 40 ± 17% for the anthropogenic source and 60 ± 20% for the oceanic source. This constraint is important for a better understanding of the global COS budget and its improved use for GPP determination.

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“…The resulting dataset represents a monthly composite of corresponding physical, chemical, and biological measurements from the offshore EMS. Such relatively high-resolution in-situ measurements can provide a platform to integrate continuous physiochemical measurements from gliders and ocean observatories (THEMO and DeepLev, (Alkalay et al 2020;Avnaim-Katav et al 2020;Katz et al 2020), as well as for biochemical and ecological models. We first compare the absolute values and temporal dynamics of primary and bacterial productivity between the EMS and other Low Nutrients Low Chlorophyll (LNLC) regions such as the North Atlantic and Pacific (HOT and BATS time-series, respectively) as well as the Red Sea.…”

Section: Discussionmentioning

confidence: 99%

“…Levantine Basin (EMS) showing the location of the THEMO-2 sampling site (the focus of this study), as well as of additional observatories and locations of long-term studies discussed here: THEMO-1, DeepLev (Katz et al 2020), N-1200 (Rosenberg et al 2020), TB-1000 (Yogev et al 2011) and the Haifa section transect cruises (Kress et al 2014;Ozer et al 2017). B) Changes in satellite-derived sea surface temperature (orange) and sea surface chlorophyll a (green) from the 1 km 2 region surrounding THEMO-2 between 2017-2020.…”

Section: Figure 1: Overview Of the Sommos Sampling Locations Context A) A Map Of Thementioning

confidence: 99%

A year in the life of the Eastern Mediterranean: Monthly dynamics of phytoplankton and bacterioplankton in an ultra-oligotrophic sea

Reich

Ben-Ezra

Belkin

et al. 2021

Preprint

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The Eastern Mediterranean Sea (EMS) is an ultra-oligotrophic, enclosed basin strongly impacted by regional and global anthropogenic stressors. Here, we describe the annual (2018-19) dynamics of phyto- and bacterioplankton (abundances, pigments and productivity) in relation to the physical and chemical conditions in the photic water column at the offshore EMS water (Station THEMO-2, ~1,500m depth, 50km offshore). Annual patterns in phytoplankton biomass (as chlorophyll a), primary and bacterial productivity differed between the mixed winter (January-April) and the thermally stratified (May-December) periods. Prochlorococcus and Synechococcus numerically dominated the picophytoplankton populations, with each clade revealing different temporal and depth patterns, while pico-eukaryotes (primarily haptophytes) were less abundant, yet likely contributed significant biomass. Integrated primary productivity (~32 gC m-2 y-1) was lower compared with other well-studied oligotrophic locations, including the north Atlantic and Pacific (HOT and BATS observatories), the western Mediterranean (DYFAMED observatory) and the Red Sea, and was on-par with the ultra-oligotrophic South Pacific Gyre. In contrast, integrated bacterial production (~11 gC m-2 y-1) was similar to other oligotrophic locations. Phytoplankton seasonal dynamics were reminiscent of those at BATS and the Red Sea, suggesting an observable effect of winter mixing in this ultra-oligotrophic location. These results highlight the ultra-oligotrophic conditions in the EMS and provide, for the first time in this region, a full-year baseline and context to ocean observatories in the region.

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The first deep-sea mooring station in the eastern Levantine basin (DeepLev), outline and insights into regional sedimentological processes

Cited by 31 publications

References 58 publications

Post-eastern Mediterranean Transient Oxygen Decline in the Deep Waters of the Southeast Mediterranean Sea Supports Weakening of Ventilation Rates

Post-eastern Mediterranean Transient Oxygen Decline in the Deep Waters of the Southeast Mediterranean Sea Supports Weakening of Ventilation Rates

Tropospheric carbonyl sulfide mass balance based on direct measurements of sulfur isotopes

A year in the life of the Eastern Mediterranean: Monthly dynamics of phytoplankton and bacterioplankton in an ultra-oligotrophic sea

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