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GEOCHEMICAL TRACERS OF ARCTIC OCEAN CIRCULATION
Christopher GuayEarth Sciences DivisionLawrence Berkeley National Laboratory
Fresh Water Cycle Maintains Stratification of Upper Arctic Ocean
Stably stratified surface layer-- ice formation-- plankton growth
Formation of cold halocline layer
Export of positive buoyancy flux to North Atlantic
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Arctic Ocean Freshwater Budget
Reference Salinity = 34.4 Goldner (1999), JGR, 104, 29,757-29,770.
FLUX
River runoffBering Strait inflowNet Precipitation (P-E)Arctic Archipelago outflowBarents Sea inflowFram Strait OutflowIceEGC Polar WaterEGC Atlantic WaterEGC Deep WaterSubtotalFram Strait InflowWSC Atlantic WaterWSC Deep WaterSubtotalNET
Q(Sv)
0.1080.81
0.012-1.371.49
-0.07-1.16-2.14-1.03-4.40
2.650.733.380.0
Salinity(PSS)
0.032.50.033.235
3.533.934.934.9
35.034.9
Effective FreshwaterFlux (km3 yr-1)
34001420380
-1460-820
-1980-560960490
-1090
-1490-340-1830
0.0
Christopher GuayESD/ LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Arctic Ocean Freshwater Budget
Reference Salinity = 34.4 Goldner (1999), JGR, 104, 29,757-29,770.
FLUX
River runoffBering Strait inflowNet Precipitation (P-E)Arctic Archipelago outflowBarents Sea inflowFram Strait OutflowIceEGC Polar WaterEGC Atlantic WaterEGC Deep WaterSubtotalFram Strait InflowWSC Atlantic WaterWSC Deep WaterSubtotalNET
Q(Sv)
0.1080.81
0.012-1.371.49
-0.07-1.16-2.14-1.03-4.40
2.650.733.380.0
Salinity(PSS)
0.032.50.033.235
3.533.934.934.9
35.034.9
Effective FreshwaterFlux (km3 yr-1)
34001420380
-1460-820
-1980-560960490
-1090
-1490-340-1830
0.0
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Discharge of Major Arctic Rivers (km3 yr-1)
Total Arctic Runoff: 3400 km3 yr-1 [10% of global total]
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Arctic Ocean Freshwater Budget
Reference Salinity = 34.4 Goldner (1999), JGR, 104, 29,757-29,770.
FLUX
River runoffBering Strait inflowNet Precipitation (P-E)Arctic Archipelago outflowBarents Sea inflowFram Strait OutflowIceEGC Polar WaterEGC Atlantic WaterEGC Deep WaterSubtotalFram Strait InflowWSC Atlantic WaterWSC Deep WaterSubtotalNET
Q(Sv)
0.1080.81
0.012-1.371.49
-0.07-1.16-2.14-1.03-4.40
2.650.733.380.0
Salinity(PSS)
0.032.50.033.235
3.533.934.934.9
35.034.9
Effective FreshwaterFlux (km3 yr-1)
34001420380
-1460-820
-1980-560960490
-1090
-1490-340-1830
0.0
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
T and S alone are not sufficient tracers of freshwater in upper Arctic Ocean
• Two major freshwater sources: Runoff and Ice-melt
• Temperature is “non-conservative” -- heat gain/loss in open water areas -- seasonal temperature variability of river runoff
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
T and S alone are not sufficient tracers of freshwater in upper Arctic Ocean
• Two major freshwater sources: Runoff and Ice-melt
• Temperature is “non-conservative” -- heat gain/loss in open water areas -- seasonal temperature variability of river runoff
• Additional conservative tracer: Oxygen isotopes
(18O/16O)sample - (18O/16O)SMOWδ18O (‰) =
(18O/16O)SMOWx 1000
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Salinity-δ18O Mass Balance for the Beaufort Sea[Macdonald et al. (2002), DSR I, 49, 1769-1785]
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
1997 Shelf-Basin Transect to Initial
SHEBA SiteMacdonald et al. (2002)DSR I, 49, 1769-1785.
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Dissolved Barium in Major Arctic Rivers
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
End-MemberConcentrations
(nmol Ba L-1)
MackenzieRiver
520
EurasianRivers
90-150
AtlanticInflow
42-45
PacificInflow
65-73
Guay and Falkner (1998)Cont Shelf Res, 18, 859- 882
1993 Surface Mixed Layer
Composite from six cruises
Guay and Falkner (1997)DSR II, 44(8), 1543-1569.
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
1997 Shelf-Basin Transect to Initial
SHEBA SiteMacdonald et al. (1999)GRL, 26(15), 2223-2226.
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Using Nutrients to Differentiate Atlantic/Pacific Waters
Jones et al. (1998), GRL, 26(6), 765-768.
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Water Mass Composition Derived FromMultiple Tracers (S, δ18O, Ba, nutrients)
1998 ARKTIS-XIV/2
Taylor et al.,JGR (in press).
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
AOMIP April Mean Sea Surface Salinity
Steele et al. (2001)GRL, 28, 2935-2938.
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Response to Shift in Atmospheric ForcingSteele and Boyd (1998), JGR, 103, 10,419-10435. Figure: I. Rigor (UW/IABP)
NegativeAO
Index
PositiveAO
Index
Weak polar vortex/high SLPAnti-cyclonic ocean circulationEurasian runoff enters at Lomonosov RidgeCold halocline formation in Eurasian Basin
Strong polar vortex/low SLPCyclonic ocean circulationEurasian runoff enters at Mendeleyev RidgeCold halocline retreat from Eurasian Basin
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Scientific QuestionsFreshwater cycle• river runoff• halocline formation• ice formation/melting
Arctic Ocean inflows/outflows• export through Canadian Archipelago
Long-term trends (relation to global climate change?)• changes in circulation regime• changes in terrestrial environment/signals• changes in biota/ecosystem• changes in carbon cycling
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Required Geochemical Measurements1. Circulation tracers
-- nutrients (N, P, Si, O2)-- stable isotopes (d18O, d13C, d15N, etc.)-- trace metals (Ba, etc.)-- radioisotopes (137Cs, 128I)-- DOC, biomarkers-- inorganic C: alkalinity, ΣCO2, DIC
2. Water mass age tracers
-- He-tritium, CFCs
3. Particulate flux tracers
-- U, Th, POC, PON
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Critical Areas
Shelf Break
• shelf-basin exchanges
• river water pathways
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Critical AreasInflows/Outflows
• communication with global ocean
• export to North Atlantic areas of deep water formation
• export through Canadian Archipelago
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Critical AreasAtlantic/Pacific Front
• boundary between Atlantic/Pacific, Eurasian/North American water mass assemblages
• Transpolar Drift
• area north of Greenland and Archipleago
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
Critical AreasBeaufort Gyre
• expands/contracts with changes in circulation regime
• storage/release of freshwater
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004
FUTURE DATA SETS NEEDED
• Long-term time series
• High-resolution (temporal and spatial) observations
Need for autonomous, in situ sensors
-- optical
-- chemical (MEMS/nanotechnology)
Christopher GuayESD/LBNL
Arctic Observing Based On Ice-Tethered PlatformsWoods Hole Oceanographic Institution, June 28, 2004