Oceanic Carbon Cycle

Transcription

1 An Intro to the Oceanic Carbon Cycle Oceanic Carbon Cycle Why is C an important element? Cellular level essential for macromolecular synthesis Trophodynamics- important in energy flow between trophic levels. biogeochemistry stoichiometry demands ties C to other - important nutrient cycles - green house properties 1

2 Four reservoirs Lithosphere Atmosphere Terrestrial biosphere Ocean Lithosphere (90,000,000) DOE /SC-108 Mauna Loa Observatory, Mauna Loa, Hawaii Anthropogenic rise in CO2 pco 2 has increase from 280 ppm to 384 ppm (2007) Increase of 40% over past 250 yrs Source: P. Tans, NOAA/CMDL Anthropogenic input is ~9 Pg C yr -1 Fossil fuel burning Cement manufacturing deforestation 2

3 ~ 4 Pg remains in the Atm Rests is removed by OCN and TB ~ 93% of C in active reservoirs is contained in the ocean Lithosphere (90,000,000) DOE /SC-108 The Chemistry of CO 2 in the Ocean Dissolution of CO 2 in seawater undergoes the following reaction: CO 2 (gas) + H 2 O H 2 CO 3 H + + HCO - 3 2H + + CO 2-3 Carbonic acid Bicarbonate Carbonate The buffering capacity of seawater: As is CO 2 dissolved in seawater, only ~1% remains as CO 2 and the rest is converted to bicarbonate and carbonate. 90% in the form of HCO 3-9% in the form of CO 3 2-1% in the form of dissolved CO 2 3

4 Time series of Atm CO 2, pco 2 and ph Doney et al Ocean CO 2 Surveys Early Ocean CO 2 surveys: GEOSECS ( ) TTO ( ) WOCE (1990 s) CLIVAR (2003 present) 4

5 Early programs did not have CRM s variability btw analytical group ±30 µmol kg -1 >1% of total signal i.e. larger than anthropogenic signal Andrew Dickson supported by NSF and DOE CRM for DIC and total Alkalinity reduced variability to ±3 µmol kg -1 Can resolve increase in TCO 2 in Surface waters BATS TCO2 (µmol kg -1 ) 5

6 Differences between pco 2 atm and pco 2 surface water.set the potential for air- sea CO 2 flux Atm pco µatm air sea CO 2 flux is driven by variability in OCE pco2 Surf OCE pco µatm global ave of pco2 in Surf OCE is ~ 7 µatm less than atm Feely et al OCE uptake of ~ 2.2 Pg C y -1 6

7 Gradients and distribution of C0 2 (DIC) over depth controls the role the ocean plays as a CO 2 sink Distribution of DIC in the OCE is controlled by 2 mechanisms: Solubility Pump- solubility of CO 2 Depth (m) DIC (µmol kg -1 ) Biological Pumpphotosynthesis & respiration 1000 Solubility Pump: Wind driven circulation Figure 5 CO 2 escapes Wind stress & Cooling CO 2 invades Equator Pole Pycnocline Upper ocean layer SINKING Thermohaline circulation Deep Ocean layer Carlson et al

8 Biological Pump Primary particles living organisms TEP fecal pellets Aggregate particles molts marine snow DOE /SC-108 Does increased delivery of nutrients from depth have a net affect on OCE uptake of atm CO 2? Michaels et al

9 Michaels et al Pumps maintain vertical gradient in DIC Depth (m) DIC (µmol kg -1 ) "Biological pump 80% 500 "Solubility pump 20% Sarmiento and Gruber

10 Estimations of Anthropogenic CO2 concentrations in the Atlantic, Pacific Indian Oceans. Sabine et al Dissolved Organic Carbon! A16 The other C reservoir 10

11 Units are g C Atmosphere 750 Figure 1 Vegetation 610 Soil and Detritus 1,580 Biota 3 DOC <700 Surface Ocean 1,020 C in Earth's crust 90,000,000 Deep Ocean 38,100 Surface sediments 150 Recoverable fossil fuel 10,000 Size spectrum of organic matter Fig. 1 mm um nm Meters Particulate Zooplankton Phytoplankton Dissolved Colloids Bacteria Pollen Viruses Sand Silt Clay Macromolecules Small Molecules Screen Sieves Filter Papers Membrane Ultrafilters Molecular Sieves Hedges

12 DOM production and removal mechanisms In the open ocean..dom production is ultimately constrained by the level of Primary production w/in a system. Carlson, 2002 Brief History and the Controversy of DOC measurements 1909 Pütter - developed first wet chemical combustion technique with chromic acid problems with chlorine interference 1934 Krogh and Keys- removed chlorine first reliable estimates of DOC 1950s- Soviets started trying high temperature combustion Duursma - wet oxidation and coulometric titration Menzel and Vaccaro - wet persulfate oxidation Armstrong - UV oxidation 1970 s - Sharp revisited the HTC method 12

13 Historical view of oceanic DOC - relatively unvarying pool of recalcitrant organic matter Menzel and Ryther 1970 DOC: The controversy new high concentrations Sugimura and Suzuki 1988 used new Pt/ alumina catalyst % higher than previous estimates AOU, DOC µm 13

14 Seattle DOM Workshop 1991 Intercalibration results 34 separate analyses of the same sample order of magnitude range in values from same sample!!! Blanks were not properly accounted for Hedges et al We have initiated over a decade long program in ocean carbon and we have no reliable estimate for DOM.you guys have to figure this out!!! -Neil Anderson NSF Chem OCE Fine tuning the instrument, column conditioning, proper blank correction, implementation of reference materials and community intercalibrations helped get to the bottom of it. 14

15 Use of referencing to resolve small variability DOC (umol /L) Surface Reference Deep Reference A22 Samples Sample # Home Made High Temperature Combustion Systems (HTC) Modified Shimadzu - High throughput!! 15

16 0 DOC and the Oceanic Carbon Cycle DOC (µm C) Partitioning the Bulk DOC Pool into Broad Pools of Lability Depth (m) Refractory Semi-labile Typical summer DOC profile - portion oceanic of bulk DOC system that is in excess of deep water DOC concentrations Mean age 3-5 k yrs old Who Cares??? Why is DOC/ DOM important? DOC (µm C) Carlson and Ducklow

17 DOC Role of mixing and DOC export DOC Temperature ( C ) and Mixed Layer Depth at BATS Depth (m) BATS core data 17

18 BATS DOC (µm C) Hansell and Carlson Relationship between the maximum depth of convective overturn and DOC export at BATS DOC export (mol C m -2 y -1 ) Max Mixed Layer Depth (m) Adapted from Hansell and Carlson

19 Potential importance of DOM stoichiometry and the biological pump Semi-labile loop Adapted from Hopkinson and Vallino

20 CO 2 fixation of C by phytoplankton grazing respiration aggregate excretion formation 2 physical and isopycnal egestion mixingof DOC break up 3 1 passive sinking of POC, PIC active vertical migration Base of euphotic zone decomposition (bacteria) consumption, repackaging (zooplankton) respiration excretion Seabed Ducklow et al