The two faces of Black Sea deoxygenation

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The two faces of Black Sea

deoxygenation

Arthur Capet1,2 _{Emil Stanev}3 _{Jean Marie Beckers}2

James Murray4 _{Marilaure Gregoire}2

1_{CNR, OGS, Trieste, Italy} 2_{University of Li `}_{ege, Li `}_ege,Belgium

3_{HZG, Helmholtz-Zentrum Geesthacht, Hamburg, Germany} 4

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Main characteristics

I Enclosed

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GHER 3D Hydrodynamic Model

Hydrostatic model, Double Sigma coordinates, Real time forcings (ECMWF)

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GHER 3D Biogeochemical Model

Provides : C, N, P, Si, O2 cycling through various forms.

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H index: Annual pressure on Benthic Ecosystems

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H response to drivers

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H response to drivers

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H response to drivers

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Vertical structure

Temperature − [°C] Salinity − [p.s.u] Brunt−Väisälä Freq. − [/s] Pot. density anom. − [kg/m3] Oxygen − [uM]

−200 −150 −100 −50 0 7 8 9 10 18 19 20 21 0.006 0.009 0.012 0.015 0.01813.5 14.0 14.5 15.0 15.5 16.016.50 100 200 300 Depth

Diagnostics of oxygen vertical structure

I Oxygen penetration depth I σθat oxygen penetration depth

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Vertical structure

Permanent Halocline −200 −150 −100 −50 0 7 8 9 10 18 19 20 21 0.006 0.009 0.012 0.015 0.01813.5 14.0 14.5 15.0 15.5 16.016.50 100 200 300 Depth

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Vertical structure

CIL Permanent Halocline Seasonal Thermocline −200 −150 −100 −50 0 7 8 9 10 18 19 20 21 0.006 0.009 0.012 0.015 0.01813.5 14.0 14.5 15.0 15.5 16.016.50 100 200 300 Depth

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Vertical structure

CIL Permanent Halocline Seasonal Thermocline Oxygen penetration depth 20 uM −200 −150 −100 −50 0 7 8 9 10 18 19 20 21 0.006 0.009 0.012 0.015 0.01813.5 14.0 14.5 15.0 15.5 16.016.50 100 200 300 Depth

I Oxygen penetration depth

I σθat oxygen penetration depth

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Vertical structure

Permanent Halocline Seasonal Thermocline Oxygen penetration depth 20 uM −200 −150 −100 −50 0 7 8 9 10 18 19 20 21 0.006 0.009 0.012 0.015 0.01813.514.014.515.015.516.016.50 100 200 300 Depth

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Vertical structure

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Profiles Data

I World Ocean database, R/V KNORR 2003, R/V Endeavour

2005

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Profiles Data

I World Ocean database, R/V KNORR 2003, R/V Endeavour

2005

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Detrending

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Interannual trends

I Oxygen penetration depth (1955 – 2015) : 140m → 90m

I Oxygen penetration σθ: 16.05 kg m−3→15.4 kg m−3

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Interannual trends

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Interannual trends

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Concerning issues

I What about the fish ?

I What about H2S ?

I What about synergy between Coastal and Open Sea deoxygenation ?

I Habitat

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Concerning issues

I What about H2S ?

May 2003 significant [H2S]

concentrations at 80m.

Oct 2005 Quasi-tropical cyclone

upwels water from 30 m depth in 5 days.

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Concerning issues

I What about H2S ?

May 2003 significant [H2S]

concentrations at 80m.

Oct 2005 Quasi-tropical cyclone upwels water from 30 m depth in 5 days.

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Concerning issues

I What about the fish ? I What about H2S ?

I What about synergy between Coastal and Open Sea

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Concerning issues

I What about the fish ? I What about H2S ?

I What about synergy between Coastal and Open Sea

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Take-home message

I Northwestern shelf: ongoing seasonal hypoxia

H response to N loads increased by

I benthic accumulation I _warming

I Open Sea : shoaling oxycline

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Take-home message

I Northwestern shelf: ongoing seasonal hypoxia

H response to N loads increased by

I benthic accumulation I _warming

I Open Sea : shoaling oxycline

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Thanks for your attention ...

... and questions

More info on :

I Seasonal hypoxia on the northwestern shelf:

Capet et al, 2012, Biogeosciences

I Decline of the Black Sea oxygen inventory:

Capet et al, 2016, Biogeosciences, In press

I DIVA detrending algorithm:

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H response to drivers

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H response to drivers

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H response to drivers

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