GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in Global Carbon Cycle Modelling Allegaten 70, N-5007 Bergen, Norway Phone: Fax: Mobile phone: DEAR STUDENT AND COLLEAGUE: ”This presentation is for teaching/learning purposes only. Do not use any material of this presentation for any purpose outside course GEOF236, ”Chemical Oceanography”, autumn 2012, University of Bergen. Thank you for your attention.”

Sarmiento&Gruber 2006 Chapter 8: Carbon cycle, part 1

Carbon diamond graphite Degens et al., 1984 Broecker, 1985

The most common elements in sea water From: Treatise in Geochemistry, Vol. 6, Elsevier, 2004 changeable ions indicated by arrows The major constituents have almost constant proportion (covary with salinity).

Ocean is vital for governing atmospheric CO 2 : K.K. Liu et al., 2010 Reservoirs and fluxes in GtC resp. GtC/yr reservoir size!

IPCC AR4, ch. 7, 2007 Global carbon cycle – pool sizes and fluxes

Carbon pool sizes and fluxes between the earth system reservoirs For carbon, reservoirs in Pg C, fluxes in Pg C yr -1. [Sundquist and Visser, in Treatise in Geochemistry, Vol. 8, Elsevier, 2004]

Source: Sarmiento&Gruber (2006) Mean annual pCO 2 difference surface ocean –atmosphere: Takahashi et al., 2002

Siegenthaler et al., 2005, Science CO 2 global T air local EPICA Dome C Taylor Dome Vostok What caused these atmospheric CO 2 changes ? Question raises a big attribution problem. Carbon in the Earth system (past glacial/interglacial) The atmospheric CO 2 concentration (past, present, future)

Mauna Loa and ice core curves on anthrop. pCO 2 increase Neftel, A., H. Friedli, E. Moor, H. Lötscher, H. Oeschger, U. Siegenthaler, and B. Stauffer Historical CO2 record from the Siple Station ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A Historical atmospheric CO2 record from ice core, Siple Station, Antarctica The atmospheric CO 2 concentration (past, present)

Mauna Loa and ice core curves on anthrop. pCO 2 increase Neftel, A., H. Friedli, E. Moor, H. Lötscher, H. Oeschger, U. Siegenthaler, and B. Stauffer Historical CO2 record from the Siple Station ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A Historical atmospheric CO2 record from ice core, Siple Station, Antarctica The atmospheric CO 2 concentration (past, present)

Preindustrial niveau 278 ppm

tropics

atmospheric CO 2 ocean land fossil fuel emissions deforestation CO 2 flux (Pg C y -1 ) Time (y) Perturbation of Global Carbon Budget ( ) Le Quéré, unpublished; Canadell et al. 2007, PNAS Anthropogenic forcing

Mean monthly pCO 2 difference surface ocean –atmosphere: Reference year 2000 Takahashi, T., et al., 2009, Climatological mean and decadal change in surface ocean pCO 2, and net sea–air CO 2 flux over the global oceans, Deep-Sea Research II, 56, 554–577

Mean annual CO 2 flux across the air water interface Takahashi, T., et al., 2009, Climatological mean and decadal change in surface ocean pCO 2, and net sea–air CO 2 flux over the global oceans, Deep-Sea Research II, 56, 554–577

CO 2 gas + H 2 O ↔ H 2 CO 3 aq ↔ HCO H + ↔ CO H + Carbon in seawater – important variables: CO 2 hydration 1 st 2 nd solution dissociation step dissociation step carbonic bicarbonate proton carbonate acid ion ion Alk = [HCO 3 - ] + 2[CO 3 2- ] + [B(OH) 4 - ] + [OH - ] – [H + ] + small terms DIC = [CO 2 + H 2 CO 3 ] + [HCO 3 - ] + [CO 3 2- ] total alkalinity, seawater property determining dissociation of weak acids dissolved inorganic carbon If 2 of the ”green” variables are known, all the others can be computed. Partial pressure of CO 2 : pCO 2 x solubility = [CO 2 ]

Sea water – buffer system! In the ocean CO 2 is highly reactive due to the ability of seawater to disscociate weak acids: CO 2 + H 2 O HCO H + CO H + HCO 3 - CO 2 + H 2 O + CO 3 2- (1+x)HCO (1-x)CO (1-x)H + 1. Dissociation step: 2. Dissociation step: CO 2 : HCO 3 - : CO : 100 : 10 Zeebe & Wolf-Gladrow, 2001

How can we quantify the different dissociation reactions? E.g. we would like to know how much [HCO 3 - ], [CO 3 2- ], and [H + ] would we have in seawater at a specific pCO 2 (CO 2 partial pressure). Black board

After: Sarmiento&Gruber (2006)

Harvey, 1955, The chemistry and fertility of seawater, Cambridge University Press. pCO 2 pH

Global mean dissolved inorganic carbon and alkalinity (horizontal averages): Source: Sarmiento&Gruber (2006)

Dissolved inorganic carbon DIC and alkalinity Alk along the ocean conveyor belt (salinity normalised values):

Property/property plot including DIC: Source: Sarmiento&Gruber (2006)

After: Sarmiento&Gruber (2006)

Heinze, C., 1990, PhD Carbon pumps