Dan Repeta 508-289-2635 [email protected] Watson BGC
MOG 2007 email list
Bertrand,Erin Marie - [email protected]
Bhatia,Maya Pilar - [email protected]
Cox,Alysia Danielle - [email protected]
Esch,Helen Carter - [email protected]
Fischer,Curt R. - [email protected]
Frame,Caitlin H - [email protected]
Gibbons,Fern Tolley - [email protected]
Lemkau,Karin Lydia - [email protected]
Lincoln,Sara Ann - [email protected]
McDonnell,Andrew - [email protected]
Noble,Abigail Emery - [email protected]
Oates,Richard Hunter - [email protected]
Ponton,Camilo - [email protected]
Richberg,Kevin - [email protected]
DOC and major carbon reservoirs and fluxes
Terrestrial Plants
900 GT C
Soil 2000 GT C
Carbonates 60,000,000 GT C
Kerogen
20,000,000 GT C
1
DOC and major carbon reservoirs and fluxes
Terrestrial Plants
900 GT C
Soil 2000 GT C
POC 15 GT C
DOC 700 GT C
Carbonates 60,000,000 GT C
150 GT C
Kerogen
20,000,000 GT C
DOC and major carbon reservoirs and fluxes
Terrestrial Plants
900 GT C
Atmosphere 750 GT (CO2)
Soil 2000 GT C
POC 15 GT C
DOC 700 GT C
Carbonates 60,000,000 GT C
150 GT C
Kerogen
20,000,000 GT C
2
DOC and major carbon reservoirs and fluxes
Terrestrial Plants
900 GT C
Atmosphere 750 GT (CO2)
Terrestrial Primary
Production 75 GT C/yr
River flux
0.5 GT C/yr
Marine Primary
Production 60-75 GT C/yr
Soil 2000 GT C
Burial 0.1-0.2
GT C/yr
POC 15 GT C
Biomass 2 GT C
DOC 700 GT C
Carbonates 60,000,000 GT C
150 GT C
Kerogen
20,000,000 GT C
Classification (definitions) of organic matter in seawater
Particulate organic carbon (POC)
3
Classification (definitions) of organic matter in seawater
Particulate organic carbon (POC)
Colloidal organic carbon (COC)
Classification (definitions) of organic matter in seawater
Particulate organic carbon (POC)
Colloidal organic carbon (COC)
Dissolved organic carbon (DOC)
Organic matter classes are defined by the filters used to
collect them !! They are operational definitions only!!!
4
The lexicon of organic matter in seawater
Dissolved organic matter; DOM (includes C, H, O, S, P…)
Dissolved organic nitrogen or phosphorus (DON, DOP)
Ultrafiltered dissolved organic matter (UDOM)
Chromophoric dissolved organic matter (CDOM)
Low and High molecular weight dissolved organic matter (LMWDOM,
HMWDOM)
Humic substances (HS) (marine humic and fulvic acids)
Analytical methods for measuring DOC
High Temperature Catalytic Oxidation
100 µL seawater
Inject directly onto
Pt or M column
Water vaporized and
trapped
DOC oxidized by Pt
to CO2
LiCOR detector
Precision + 0.5- 1µM
5
Analytical methods for measuring DOC
UV photooxidation
Chemical oxidation
Add acid, sparge
add persulfate
Heat 24 hr
Sparge
Measure CO2
Used for large volume samples (stable and radioisotope analyses)
Vertical profiles of dissolved organic carbon in the ocean
TOC (µM)
Measured by HTCO
Often measured as TOC
Surface values typically 60-80 µM
Deep water values @ 40 +1 µM
(implies some unknown feedback/
control of DOC values)
Global inventory about 680 GT C
Data from Peltzer and Hayward (1996) DSR
6
Distribution of DOC in the Pacific and Atlantic Basins
Data from Dennis Hansell
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
Distribution of DOC in the Pacific and Atlantic Basins
Mar 06
Jun 03
Jan 05
Data from Dennis Hansell
Feb 03
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
7
A16
P16
A16
P16
8
A16
P16
A16: DOC on δθ 26.4 – 26.7
Depth (m)
Input on the Equator
(solubilization of sinking particles
or advective input?)
Data from Dennis Hansell
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
9
A16: DOC on δθ 27.0 – 27.3
Depth (m)
Data from Dennis Hansell
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
A16: DOC on δθ 27.0 – 27.3
Data from Dennis Hansell
Depth (m)
Expected Mixin
g Curve
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
10
P16: DOC on δθ 26.4 – 26.7
Depth (m)
Input on the equator
(sinking particles?)
Data from Dennis Hansell
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
P16: DOC on δθ 27.75– 28.0
Depth (m)
Decrease in the far
north North Pacific
Data from Dennis Hansell
(www.rsmas.miami.edu/groups/biogeochem/Data.htm)
11
DOC in the Deep Global Ocean (Hansell and Carlson, 1998)
Annual cycle of DOC production in the mixed layer at BATS*
*Bermuda Atlantic Time Series, a JGOFs LTEM site
Carlson et al.1994; Nature
12
Interannual variations in DOC concentration and inventory at BATS
1994
1995
1996
1997
1998
0.4-1.4 mol C m-2 removed in overturn (10-41% C remineralized)
Accumulation of DOC in the tropical N. Pacific Ocean (HOTS)
0
100
200
Church et al L&O 2002
93 94 95 96 97 98 99 00
13
Export of DOC from the surface to the mesopelagic ocean
DOC and AOU- why is there a relationship?
Data from Peltzer and Hayward, 1996 DSR II v 43 p1155
14
Natural abundance radiocarbon and DOC
DOC cycling via DO14C
UV photooxidation
Depth
Δ14C(‰)
Age
1880m
-351 ‰
-3470+330 ybp
1920m
-341 ‰
-3350+300 ybp
Williams, Oeschger, and Kinney; Nature v224 (1969)
15
Accelerator Mass Spectrometry (AMS)
NOSAMS at Woods Hole
C-14 PP measurements use 106x more C-14 than natural abundance!!!!!
Radiocarbon in the Atlantic and Pacific Oceans
Peter M. Williams and Ellen Druffel; Nature 1987, JGR 1992
16
Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is always older than DIC
(by 4 kyrs in surface water)
DIC-> POC -> DOC
17
Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is always older than DIC
(by 4 kyrs in surface water)
ΔΔ14C of DIC and DOC
is about the same in the
deep Atlantic and Pacific
Radiocarbon in the Atlantic and Pacific Oceans
DIC 14C in surface waters
of the Atlantic and Pacific
has the same isotopic value.
DOC is always older than DIC
(by 4 kyrs in surface water)
ΔΔ14C of DIC and DOC
is about the same in the
deep Atlantic and Pacific
Deep ocean values of DOC
are equal to a radiocarbon
age of 4-6 kyrs
Either there is a source of
“old” DOC, or DOC persists
for several ocean mixing
cycles
18
DO14C and DI14C in different A/P/S ocean basins
Depth (m)
Δ14C
Druffel et al., 1992; Druffel and Bauer, 1998
DO14C and DI14C in different A/P/S ocean basins
Depth (m)
Δ14C
Druffel et al., 1992; Druffel and Bauer, 1998
19
DOC cycling in surface seawater
DOCΔ14C
(DIC=150‰)
Druffel et al. (1992) JGR
DOC cycling in surface seawater
DOCΔ14C
(DIC=150‰)
Δ14C = DOC(deep)
Old DOC
New DOC
Δ14C=DIC
Druffel et al. (1992) JGR
20
Radiocarbon Mass Balance For Surface Ocean DOC
DOC sfc = DOCdeep + DOC xs
Δ14Csfc DOC sfc = Δ14Cdeep DOC deep + Δ14C xs DOC xs
where Δ14Cxs = DI14Csfc and deep = (3500-4000 m)
After Williams and Druffel, 1987
LOCATION
DATE
DI14C
PO14Csusp
DO14Ccalc
DO14Cmeas
Sargasso Sea (31º50’N, 63º60’W)
1989
127 ‰
138 ‰
-214 ‰
-210 ‰
North Central Pacific (31ºN,
159ºW)
1987
135 ‰
147±16 ‰
-155 ‰
-153 ‰
Southern Ocean (54°S, 176°W)
1995
25 ‰.
32 ‰
-398 ‰
-372 ‰
Druffel et al., 1992; Druffel and Bauer, 1998
Using a simple 2 component mixing model of old “non-reactive” DOC
with deep sea 14C and [DOC] values, and a new “reactive” component with
DICΔ 14C, and [DOC] = [DOC]total-[DOC]deep,
Modeled and measured DOC 14C values agree pretty well…
DOC Δ14C
DOC Δ14C
Sargasso Sea
N. Pacific
Depth
Williams and Druffel, 1987; Druffel et al. 1992
21
Two Endmember Carbon Mass Balance Reproduces the Δ14C Depth
Profile of DOC (Requires Addition of DOC from Sinking Particles)
(Mortazani and Chanton, 2004)
0
Δ14Cxs
Eastern North Pacific
-100
14
Δ C-DOC (‰)
Southern Ocean
73±23‰ (’91-’95)
105±62‰ (’95/’96)
135±26‰ (’89)
162 ±39‰ (‘87)
North Atlantic
-200
Central North Pacific
-300
-400
-500
-600
0.01
0.015
0.02
0.025
0.03
0.035
1/[DOC] (μM)
Δ 14 C = Δ 14 C + ( 1
)( DOC Δ 14 C b − DOC b Δ 14 C )
DOC
z
xs
b
xs
z
Radiocarbon measurements show that the average age
of deep sea DOC is > 5000 yr. If the global inventory is
700 GT C, then the annual flux of C to maintain the system
at steady state can be calculated as:
700 GT/ 5000 yr = 0.14 GT C yr-1
The annual input of DOC from rivers is 0.2-0.4 GT C yr-1,
while annual marine primary production is 60-75 GT Cyr-1
Either source adds enough C per year to maintain the system.
So what is the source of oceanic DOC?
22
What is the source of oceanic DOC ?
Druffel et al., JGR 1992
Stable C isotopes
Marine C
-21‰
Terrestrial C
C3 plants -27‰
C4 plants -15‰
23
Today’s highlights
DOC is operationally defined by the filter used.
DOC is the largest reservoir of organic carbon in seawater (>98%
of organic carbon). It has high concentrations
in the euphotic zone indicating net production (or at least input).
Values at depth are low (about half surface water values) and nearly
constant throughout much of the deep ocean.
DOC values are highest where mixing is the least. Mixing
exports DOC to the meso- and bathypelagic ocean where it is oxidized.
Deep oxidation represents about 20% of NCP and AOU.
Radiocarbon values of DOC enriched in surface waters but highly
depleted at depth. They can be modeled as two end member mixing.
Deep sea values are consistent with an average residence time of
5000-6000 years. Several ocean mixing cycles!!! No one knows why,
but surely this impacts organic nutrients.
A16
P16
24
Seasonal accumulation of DOC in the mixed layer at BATS
Σ 250 m
100-250 m
25