Salinity distribution in the Oceans Average practical salinity of open ocean waters 34.72 http://eps.mcgill.ca/~courses/c542/ 1/58
Salinity distribution in the Oceans Factors that control seawater salinity: 1) Evaporation 2) Precipitation (rainfall) 3) Concentration of salts in freezing seawater 4) Dilution with melting ice 5) Continental runoff 6) Transport by ocean currents 7) Mixing 8) Seepage of groundwater 9) Dissolution of ancient evaporite deposits and salt domes Whereas the first five are effective only at the sea surface, at depth, the salinity distribution is governed almost exclusively by 6) and 7). Other factors (e.g., 8) and 9)) are only of local significance. 2/58
Salinity distribution in the Oceans (the balance between evaporation and precipitation) 3/58
Salinity distribution in the Oceans (evaporation and precipitation atmospheric circulation) Jet stream 4/58
Earth Global Circulation 5/58
The surface currents of the world oceans Pacific Ocean Atlantic Ocean Southern Ocean 6/58
Salinity distribution in the Oceans (ice formation and brine rejection) Brine channels Ice stalactites 7/58
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Salinity distribution in the Oceans (stratified and mixed estuaries) 9/58
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Strait of Belle-Isle LOWER UPPER RIVER Cabot Strait Freshwater discharge = 11,900 m 3 s -1 11/58
The St. Lawrence Estuary (a partially stratified estuary) 1 2 1 1 2 2 12/58
Anticosti Channel Esquiman Channel Tadoussac Rimouski Trois-Pistoles Cabot Strait 13/58
The St. Lawrence Estuary, Gulf and continental shelf Belle-Isles Strait Tadoussac Laurentian Trough Anticosti Channel Esquiman Channel Rimouski Cabot Strait Laurentian Trough 14/58
R/V CORIOLIS II 15/58
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The St. Lawrence Estuary (a partially stratified estuary) 0 IML2002066, 07-NOV-2002 14:47:23-100 Depth (m) -200-300 -400 10 20 30 40 50 60 70 80 90 Oxygen saturation (%) 0 1 2 3 4 5 6 Temperature ( C) 28 29 30 31 32 33 34 35 36 Salinity 23 23.5 24 24.5 25 25.5 26 26.5 27 27.5 28 Density σ (kg m -3 ) 18/58
0 100 The St. Lawrence Estuary (a partially stratified estuary) Lower St- Lawrence Estuary Gulf of St-Lawrence Surface Layer Intermediate (Cold) Layer (<0 C) Atlantic Continental Shelf Depth (m) 200 300 Deep Layer (S= 34.6 T= ~5 C) 400 500 TADOUSSAC CABOT STRAIT 0 200 400 600 800 1000 1200 1400 Distance from Quebec City (km) 19/58
0 100 The St. Lawrence Estuary (a partially stratified estuary) Lower St- Lawrence Estuary Gulf of St-Lawrence Surface Layer Intermediate (Cold) Layer (<0 C) Atlantic Continental Shelf Depth (m) 200 300 Deep Layer (S= 34.6 T= ~5 C) 400 500 TADOUSSAC CABOT STRAIT 0 200 400 600 800 1000 1200 1400 Distance from Quebec City (km) 20/58
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The Saguenay Fjord 22/58
Salinity distribution in the Oceans (ocean currents and circulation) 23/58
Salinity distribution in the Oceans (ocean currents and circulation) Salinity 34.5 1000 T Depth (m) 2000 3000 24/58
Salinity distribution in the Oceans (ocean currents and circulation) 25/58
Salinity distribution in the Oceans (ocean currents and circulation) 26/58
Salinity distribution in the Oceans (ocean currents and circulation) AAIW AADW AABW AABW Antarctic Bottom Water AADW Antarctic Deep Water AAIW Antarctic Intermediate Water NADW North Atlantic Deep Water 27/58
Salinity distribution in the Oceans (ocean currents and circulation) AABW 28/58
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The thermohaline circulation 30/58
Salinity distribution in the Oceans (the signature of water masses and T-S diagrams) 31/58
Geochemical tracers of ocean circulation t 1/2 = 12.32 yrs t 1/2 = 5730 yrs One TU = 1 atom of tritium for every 10 18 atoms of hydrogen. 32/58
Geochemical tracers of ocean circulation = ventilation time or age of the water mass 33/58
Geochemical tracers of ocean circulation Atlantic Ocean 34/58
Geochemical tracers of ocean circulation 35/58
The thermohaline circulation 36/58
Salinity distribution in the Oceans (the signature of water masses and T-S diagrams) 37/58
Salinity distribution in the Oceans (mixing and caballing) T mix (m 1 T 1 + m 2 T 2 )/(m 1 + m 2 ) S mix = (m 1 S 1 + m 2 S 2 )/(m 1 + m 2 ) 38/58
Long-term mean temperature, salinity and DO saturation estimated on the 27.25 kg m -3 potential density surface. Gilbert et al., Limnol. Oceanogr. (2005) 39/58
Salinity distribution in the Oceans (mixing, caballing and tie lines) 1930 72% Labrador/28% WC Atlantic 1985 53% Labrador/47% WC Atlantic Gilbert et al., Limnol. Oceanogr. (2005) 40/58
Validity of the law of constant relative proportions 1. Estuarine Mixing 2. Anoxic Basins 3. Freezing 4. Precipitation and Dissolution 5. Evaporation 6. Submarine Volcanism 7. Admixture with Brines 8. Diagenesis 41/58
River compositions Europe Africa Asia K + Ca 2+ Mg 2+ Na + Cl - SiO 2 SO 4 2- HCO 3 - NO 3 - Mg 2+ Ca 2+ Na + Cl - SiO 2 SO 4 2- HCO 3 - K + Ca 2+ Mg 2+ Na + Cl - SiO 2 SO 4 2- HCO 3 - NO 3 - N. America S. America Australia K + Mg 2+ Ca 2+ Na + SiO Cl - 2 SO 4 2- HCO 3 - K + Cl - SO 4 2- Ca 2+ Mg 2+ Na + SiO 2 - HCO 3 K + SO 4 2- Ca 2+ Mg 2+ Na + Cl - SiO 2 HCO 3-42/58
Seawater and mean river compositions Seawater River Water Ca 2+ Mg 2+ Na + K + Ca 2+ Mg 2+ SO 4 2- K + SO 4 2- Na + Cl - Cl - SiO 2 HCO 3-43/58
Anoxic basin Sea River S = 10 S =35 O 2 H 2 S SO 4 2- + 2 CH 2 O H 2 S + 2 HCO 3-44/58
Anoxic basin (Black Sea) 0 TEMPERATURE ( o C) 6 8 10 12 14 SIGMA - T 10 12 14 16 18 0 50 50 100 100 DEPTH (m) 150 200 250 S DEPTH (m) 150 200 250 300 350 t 300 350 400 18 19 20 21 22 SALINITY 400 45/58
Anoxic basin (Black Sea) Mn (µm) 0 2 4 6 8 10 0 Co (nm) 0 1 2 3 4 5 0 Ni (nm) 0 2 4 6 8 10 12 0 Cu (nm) 0 2 4 6 8 0 400 400 400 400 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 2000 2000 2000 2000 Fe (nm) 0 100 200 300 0 Pb (pm) 0 40 80 120 0 Cd (pm) 0 50 100 150 200 0 Zn (nm) 0 2 4 6 8 10 12 0 400 400 400 400 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 DEPTH (m) 800 1200 1600 2000 2000 2000 2000 46/58
Anoxic basin (Framvaren Fjord, Norway) 47/58
Anoxic basin (Framvaren Fjord, Norway) Salinity 12 14 16 18 20 22 24 O 2 (µm) 0 50 100 150 200 250 300 350 0 20 40 Oxygen DEPTH (m) Temp. Salinity σ t DEPTH (m) 60 80 100 120 Sulfide 140 160 6 8 10 12 14 16 18 20 Temperature ( o C) and Sigma-T 180 0 2 4 6 8 H 2 S (mm) SO 4 2- + 2 CH 2 O H 2 S + 2 HCO 3-48/58
Anoxic basin (Framvaren Fjord, Norway) 0 Mn (µm) 0 4 8 12 16 Co (nm) 0 2 4 6 8 10 0 Ni (nm) 0 2 4 6 8 0 Cu (nm) 0 2 4 6 0 40 40 40 40 DEPTH (m) 80 120 DEPTH (m) 80 120 DEPTH (m) 80 120 DEPTH (m) 80 120 160 160 160 160 200 200 200 200 Fe (nm) Pb (pm) Cd (pm) Zn (nm) 0 500 1000 1500 2000 0 0 200 400 600 0 0 200 400 600 0 0 20 40 60 0 40 40 40 40 DEPTH (m) 80 120 DEPTH (m) 80 120 DEPTH (m) 80 120 DEPTH (m) 80 120 160 160 160 160 200 200 200 200 49/58
Anoxic basin (Framvaren Fjord, Norway) TCO 2 (mm) 0 4 8 12 16 20 24 DEPTH (m) O 2, H 2 S (µm) 0 40 80 120 160 200 240 280 8 10 12 14 16 18 20 22 24 26 Fe(II) Mn(II) Oxygen Sulfide 28 0 4 8 12 16 20 Mn(II) (µm) 0 1 2 3 4 5 Fe(II) (µm) DEPTH (m) ph 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 0 20 40 60 80 100 120 140 160 180 ph TCO 2 TA 200 0 4 8 12 16 20 TA (mm) 50/58
Anoxic basin (Cariaco Trench) SALINITY 20 22 24 26 28 30 32 34 36 38 40 0 [O 2 ] (µm) 0 50 100 150 200 250 0 TA (mmol kg -1 ) 2.3 2.4 2.5 2.6 2.7 2.8 ph 7.8 8.0 8.2 8.4 0 200 Temp. 200 Oxygen 200 DEPTH (m) 400 600 800 1000 Sigma-T Salinity DEPTH (m) 400 600 800 1000 Sulfide DEPTH (m) 400 600 800 1000 ph TA TCO 2 1200 1200 1200 1400 15 20 25 30 TEMPERATURE ( o C) 1400 0 20 40 60 [H 2 S] (µm) 1400 2.0 2.1 2.2 2.3 2.4 2.5 TCO 2 (mmol kg-1 ) 51/58
Freezing (ice formation and brine rejection) Brine channels Besides excluding salts when ice forms, some differential fractionation of the major ions takes place during freezing. For example, sea ice retains proportionally more sulfate than chloride and, consequently, the SO 4 2- :Cl - ratio is lowered in the residual water. 52/58
Precipitation of minerals Bahamas Banks Ca 2+ + CO 3 2- CaCO 3(s) 53/58
Precipitation of minerals/evaporation (evaporative basins) Ca 2+ + CO 3 2- CaCO 3(s) Ca 2+ + SO 4 2- + 2 H 2 O CaSO 4 2H 2 O (s) Na + + Cl - NaCl (s) 54/58
Submarine volcanism Water debouching from hydrothermal vents at mid-ocean ridges are devoid of Mg 2+ and SO 4 2- but rich in trace metals. 55/58
Admixture of brines/mineral dissolution (Orca Basin) NaCl (s) Na + + Cl - CaSO 4 2H 2 O (s) Ca 2+ + SO 4 2- + 2 H 2 O 56/58
Admixture of brines/dissolution of minerals (Red Sea) NaCl (s) Na + + Cl - CaSO 4 2H 2 O (s) Ca 2+ + SO 4 2- + 2 H 2 O 57/58
Diagenesis The degradation of organic matter in the sediments, the precipitation of authigenic minerals, the dissolution of detrital or biogenic minerals and the interactions (adsorption) with solids in the sediment result in significant variations of the relative elemental concentration ratios. 58/58