Inactive and relict rock glaciers of the Deboullie Lakes ...
Old carbon in the modern marine environment€¦ · · 2007-04-20• 2. Relict OC (“kerogen”)...
Transcript of Old carbon in the modern marine environment€¦ · · 2007-04-20• 2. Relict OC (“kerogen”)...
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Old carbon in the modern marine environment
Possible origin(s) of non-zero 14C ages for OC carbon in marine surface sediments:
• 1. Delivery of “pre-aged” terrestrial OC of vascular plant origin
• 2. Relict OC (“kerogen”) inputs from erosion of sedimentary rocks
• 3. Sediment redistribution processes- Bioturbation- Lateral advection
• 4. Black Carbon
The Global Organic Carbon Cycle (ca. 1950)
ATMOSPHERIC CO2(750)
SEDIMENTARY ROCKS
(KEROGEN) (15,000,000)
-20 to -35‰t = infinite
LAND PLANTS (570)
-25 to -30‰ (C3) -14 to -20‰ (C4)
t = 0 yr
SOIL HUMUS (1,600)
-25 to -30‰ (C3) -14 to -20‰ (C4) t =10-10,000 yr
OCEAN (BIOTA) (3)
-20 to -30‰ (C3) t = 400 yr
RECENT SEDIMENTS (100)
-20 to -25‰t = ?? yr
uplift
burial
physical weathering
(0.2)
net terrestrial primary production
(50)
humification(50)
river or eoliantransport
(POC=0.15)
fossil fuel utilization
OC preservation (0.15)
(units=1015gC)
Modified after Hedges (1992)
net marine primary
production (50)
sediment redistribution
2
0
1
2
3
4
5
6
-250 -150 -50 50 150 250
∆14C
z (c
m)
1899
1913
1937
1961
1985
1996
Benthic forams
TOC
Planktonic forams
DIC
TOC and foraminiferal ∆14C in Santa Monica Basin sediments
-200
-150
-100
-50
0
50
100
150
-35 -30 -25 -20 -15δ13C
∆14
C
SMB 0-1SBB 0-1SMB 5-6-86 ± 19 ‰
+59 ± 26 ‰
SMB, TOC
SMB, TOC
14C contents of algal sterols in CBB sediments
Post-bomb DIC
Pre-bomb DIC
Data from Pearson et al. (2000)
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Ross Sea, Antarctica
2760-24.041.05827Chinstrap
6500-26.350.49670Emperor
4070-27.420.34623Gentoo
9990-25.650.24671Fairy
14C age
δ13CTOC (%)
Water Depth
(m)
SiteSurface Sedimentary OC composition
Data source:Ohkouchi et al. (2003)
Ross Sea
Antarctica
C14 fatty acidC16 fatty acidC18 fatty acidTOC
0
5
10
15
Dep
th in
cor
e (c
m)
Calendar year (yr BP)
Post
-bom
b D
IC
Pre-
bom
b D
IC
0 1000 2000 3000 4000
Fatty acid and TOC 14C chronologies for Ross Sea sediments
(OxCal3 calibration)
Data source:Ohkouchi et al. (2003)
Chinstrap Site
15 cm/kyr
7.5 cm/kyr
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Coupled molecular and microfossil 14C measurementsPremise:
• Marine algal biomarker compounds (e.g., alkenones) and planktonic forams both encode surface ocean-derived signatures (incl. 14C content of DIC).
• Age discrepancies must therefore indicate different subsequent fates.
• Marine organic matter is predominantly associated with the fine fraction of sediments – prone to resuspension and redistribution.
• Foraminiferal tests are coarse, sand-sized particles – less susceptible to redistribution by bottom currents.
Approach:
• Use 14C relationships between planktonic foraminifera, algal biomarkers (e.g., alkenones), and bulk OC isolated from the same sediment intervals as a tool to examine sedimentological processes (lateral transport, bioturbation).
C37 “alkenone” E. Huxleyi
0
500
1000
1500
2000
10 20 30
%CaCO3
Age
(Cal
enda
r yea
rs)
0.6 0.8
UK37'
0 5000
alkenones0 5000
TOC0 5000
FFIC
Age difference (vs planktonic forams)
Ohkouchi et al. 2002
Sedimentological Controls on Geochemical Records from the Bermuda Rise
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Cape Cod
Nova Scotia
Bermuda
SeaWiFS satellite image of E. huxleyibloom off Newfoundland in the western Atlantic on 21st July, 1999.
6
?
Long-range transport of organic matter (and alkenones) from the ScotianMargin to the Bermuda Rise?
?
Lateral transport of organic matter to the Bermuda Rise
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?
Lateral transport of organic matter to the Bermuda Rise
Sources and Transport of Alkenones and Forams to the Bermuda Rise
SCOTIAN MARGIN
TERRIGENOUS SEDIMENT
PARTICLE RESUSPENSION
PLANKTONIC FORAMS
CaCO3
WARM ALKENONES
COLD ALKENONES
BERMUDA RISE
SCOTIAN MARGIN
TERRIGENOUS SEDIMENT
PLANKTONIC FORAMS
CaCO3
WARM ALKENONES
COLD ALKENONES
BERMUDA RISE
N
N
ADVECTION OF OLD, COLD ALKENONES ON
CLAYS/SILTS
PRESENT DAY
LITTLE ICE AGE
FOCUSSING
FOCUSSING
SARGASSO SEA
SARGASSO SEA
ADVECTION OF OLD, COLD ALKENONES ON
CLAYS/SILTSLAURENTIANFAN
LAURENTIANFAN
PARTICLE RESUSPENSION
COLD SST
COLD SST
WARM SST
WARM SST
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Science goes in circles!
HEBBLEStudy area
Namibian margin (Benguela Upwelling region)
Namibia
-5500
-4500
-3500
-2500
-1500
-500
0
1000
Elevation
(m)
0-2 cmalkenones and bulk OC
modern age
2-12 cm (pre-bomb)alkenones: 1180 yrs
~ Reservoir age
0-1 cmalkenones 2500 yrbulk OC 2270 yrforaminifera 25 yr
Data from Mollenhauer et al., 2003
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14C ages of Namibian margin sedimentary components (core 226660-5)
160
140
120
100
80
60
40
20
0
0 5000 10000 15000
Total organiccarbon
Alkenones
14C age (yr)
Dep
th (c
m)
Plantonic forams( G. bulloides)
Alkenones
Total organiccarbon
0 1000 2000 3000 4000 5000
14C age difference vs forams (yr)
Mollenhauer et al., 2003
Accumulation maximum (depocenter) on upper continental slope
20 m
Distance [km] 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
Wat
er D
epth
[m]
(Vp=
1500
m/s
)
1000
1600
1400
1200
SNa)
b)
erosion?increased
accumulation
Seismic data processing: André Janke
TOC
(%)
012345678910
8 9 10 11 12 13 14 15 16 17
-30
-29
-28
-27
-26
-25
-24
-23
-22
-21
-20
-19
Walvis Bay
Lüderitz
Sites of increasedaccumulation in protectedlocations (depocenters):Implication of currentcontrolled sedimentation
Mollenhauer et al., 2002
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Southern Chile
0
2000
4000
6000
8000
Con
vent
iona
l 14C
age
(yr B
P) GeoB3313-1
Chile
0 200 400 600 800Core depth (cm)
-10000
10002000300040005000
∆14
C a
ge (y
r)
bulk OC
planktic foraminifera
alkenones
alkenones - forams
bulk OC - forams
Chile
Mollenhauer et al. In press.
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
Age
diffe
renc
e (14
C y
ears
)
Sample
Bermuda Rise Namibian Slope Chilean Margin NW African Slope Santa Barbara Basin Namibian Shelf Scotian Shelf (Emerald Basin) New England Shelf (Mud Patch) Gulf of Mexico Oman Margin Indian Ocean
Closed symbols = Alkenone-foram age discrepancyOpen symbols = TOC-foram age discrepancy
14C age discrepancies between organic matter and calcareous microfossils
Eglinton et al. unpublished
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-10
0
10
20
30
40
50
60
Adve
cted
alk
enon
e co
ntrib
utio
n (%
) Bermuda Rise Benguela Scotian Margin New England margin Gulf of Mexico Arabian Sea Santa Barbara Basin Indian Ocean NE Pacific Ocean ( (Stn M))
Estimates of advective alkenone contributions
Assumptions:∆14C of indigenous alkenones = ∆14C of forams∆14C of advected alkenones = -1000 permil (infinite 14C age)
Eglinton et al. unpublished
-600 -500 -400 -300 -200 -100 0 100
-600
-500
-400
-300
-200
-100
0
100
∆14
C a
lken
ones
(per
mil)
∆14C bulk OC (permil)
Core tops only (0-5 cm)
Eglinton et al, unpublished
Comparison of alkenone and TOC 14C agesin surficial (< 3 cm) marine sediments
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Additional evidence for advective OC supplyto the sea floor
(i) Increased material fluxes in deep, relative to shallow, sediment traps deployed near continental slopes (Honjo et al., 1982; Biscaye et al., 1988; Thomsen & van Weering, 1998).
(ii) High suspended particle concentrations near the seafloor (bottom nepheloid layer; McCave, 1983; Gardner & Sullivan, 1981) or associated with the detachment of intermediate nepheloid layers from the upper slope (INLs; Biscaye et al., 1988; Pickart, 2000).
(iii) Carbon and oxygen imbalances in the deep ocean (Jahnke et al., 1996).
(iv) Old 14C ages of OC on suspended particles in slope waters (Bauer et al., 2001).
(v) 14C age of particles on slope waters intercepted by sediment traps (Anderson et al., 1994; Hwang et al., 2004).
(vi) The isotopic and molecular composition of deep sea sediments (Freudenthal et al.,2001; Benthien & Müller, 2000).
Advection of POC in the Panama Basin
Druffel et al., 1998
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Benthien & Muller, 2000
Lateral transport of alkenones to the Argentine Basin
Vertical Transport of Organic Matter to the Sea Floor
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Lateral Transport of Organic Matter to the Sea Floor
-1000
-800
-600
-400
-200
0
G. r
uber G. i
nfla
ta
TOC
(0-1
cm)
TOC
(1-2
cm)
Alke
none
s (0
-1cm
)Al
keno
nes
(1-2
cm)
C16
fatty
aci
dC
18 fa
tty a
cid
C24
fatty
aci
dC
26 fa
tty a
cid
C28
fatty
aci
d
C21
+C23
+C25
alk
anes
C22
+C24
+C26
alk
anes
C27
alk
ane
C29
+C31
alk
anes
C28
+C30
+C32
alk
anes
UC
M
∆14
C (p
erm
il)
planktonic forams total organic carbon alkenones fatty acids hydrocarbons
14C age variability in Bermuda Rise surface (0-3 cm) sediment
0
1000
2000
3000
4000
5000
10000
15000
2000030000
14C age (yr B
P)
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Calculation of % terrestrial, marine and fossil OC
∆14CTOC = fmarine * ∆marine + fterrestrial * ∆terrestrial + ffossil * ∆fossil
δ13CTOC = fmarine * δmarine + fterrestrial * δterrestrial + ffossil * δfossil
fmarine + fterrestrial + ffossil = 1
Variable Measurement/assumption:∆14CTOC measure directly (AMS)δ13CTOC measure directly (irMS)∆14Cmarine measure phytoplankton sterol (PCGC/AMS)∆14Cterrestrial measure lignin phenol/plant wax (PCGC/AMS)∆14Cfossil stipulate as –1000 ‰δ13Cmarine measure phytoplankton sterol (irm-GC-MS)
- assume offset between biomarker and bulk OCδ13Cterrestrial measure lignin phenol/plant wax (irm-GC-MS)
- assume offset between biomarker and bulk OCδ13Cfossil assume value based on regional stratigraphy
- (or measure biomarker selected based on ∆14C)
Dual isotopic mass balance approach:
Arab
ian
Sea
Beng
uela
Upw
ellin
Sant
a M
onic
a Ba
sin
Blac
k Se
a U
nit I
Blac
k Se
a U
nit I
I
Berm
uda
Ris
e
Was
hing
ton
Mar
gin
St2
Was
hing
ton
Mar
gin
St1
Gul
f Of M
exic
o
Beau
fort
Sea
Ros
s Se
a (C
hins
tra
Ros
s Se
a (G
ento
o)
Ros
s Se
a (E
mpe
ror)
Ros
s Se
a (F
airy
)
Arabian Sea
Benguela Upwelling
Santa Monica Basin
Black Sea Unit I
Black Sea Unit II
Bermuda Rise
Washington Margin St2
Washington Margin St1
Gulf Of Mexico
Beaufort Sea
Ross Sea (Chinstrap)
Ross Sea (Gentoo)
Ross Sea (Emperor)
Ross Sea (Fairy)
0
10
20
30
40
50
60
70
80
90
100-712
-25.65-555
-26.35-395
-27.42-300
-24.04-600
-22.68-251-20.7
∆14C TOCδ13C TOC
-109-21.7
-160-23.0
-108-24.2
-876-28.26
-136-25.24
-468-25.36
-570-21.7
-194-25.29
%
marine vascular plant relict
Dual Isotope Mass Balance
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Black Carbon (BC)
Suggested Reading:
• Gustafsson O. and Gschwend P.M. (1998) The flux of black carbon to surface sediments on the New England continental shelf. Geochim. Cosmochim. Acta 18, 805-829.
• Masiello C.A. and Druffel E.R.M. (1998) Black Carbon in Deep-Sea Sediments. Science 280, 1911-1913.
• Schmidt M.W.I. and Noack a.g. (2000) Black carbon in soils and sediments: Analysis, distribution, implications and current challenges. GBC 14, 777-793.
• Masiello C.A. (2004) New directions in black carbon organic geochemistry. Mar. Chem. 92, 201-213.
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Black Carbon (BC)
Some Notes:• Estimates of modern BC production• Biomass burning: 50-260 Tg C/year• Fossil fuel combustion: 12-24 Tg C/year• Atmospheric lifetime of BC aerosols: 40 hours to 1 month• Mass of organic carbon stored globally in ocean sediments: 160 Tg/year • BC estimated to make up ca. 6% of sedimentary OC globally.• Locally (on margins) BC may comprise up to 50% of TOC.
Tons emitted Tons emitted
50000
20000
10000
5000
1000
5000
1000
500
100
10
Biomass BurningFossil Fuel Combustion
Scatter Absorb
Contributions of Black Carbonto Greenhouse Warming
BCOther particulateaerosols
Cooke & Wilson (1996)
Kirkevag et al. (1999)
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Public Health
Increased respiratory problemsassociated with elevated particulatematter concentrations
Black Carbon – A moving Target!(The Combustion Continuum)
Schmidt et al. (1999)
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BC isolation/measurement methods
3 main types of method:• optical• chemical oxidation• thermal oxidation
NB: In almost all cases, BC is operationally defined.– Leads to very different estimates of quantity and flux of BC.
Carbon isotopic characterization of BC based
on thermal oxidation(“Gustafsson”) method
Modified by Reddy
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Glacial
Interglacial
Verardo & Ruddiman (1996)200
180
160
140
120
100
80
60
40
20
00.0 0.2 0.4 0.6 0.8 1.0 1.2
Charcoal (%)
Age
(ka)
Middelburg et al. (1999)
Supply of BC to marine sediments
Proportions of BC in marine sediments
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14C age of Black Carbon in marine sediments
Masiello and Druffel 1998, Science
Non-BC BCNB. BC isolated by chemical wet oxidation method
BC in Santa Clara River suspended sediments
Masiello and Druffel, 2001, GBC
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BC in Santa Monica Basin sediments
Masiello and Druffel 2003 GRL
Proportions of BC in marine sediments
Middleburg et al 1999
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Graphitic Black Carbon (GBC) in(pre-anthropogenic) Washington Margin sediments
Dickens et al. 2004, Nature
Guo et al. 2004, GBC
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649 ± 143-80.8-27.912 µgPlant wax alcohols
2070 ± 35-231.7-15.130.24 %Black Carbon
1260 ± 40-149.6-18.931.02 %Total Organic Carbon
14C age(yr BP)
∆14C(‰)
δ13C(‰)
Concn. (gdw basis)Fractions
Eglinton et al., G3, 2002
Carbon isotopic composition of dustfall sample off NW Africa
Molecular Proxies for BC
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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
1880
1900
1920
1940
1960
1980
0.000 0.002 0.004 0.006 0.008
Year
of D
epos
ition
Organic Carbon (g OC / g sed)
Soot Carbon (g SC / g sed)0 4 8 12 16
1880
1900
1920
1940
1960
1980
PAH concentration (ug/g)
Gustafsson et al. (1997)
Historical records of combustion inputs to the environment
Pre-1880’s: Wood Combustion
1900-1950: Heavy industrializationUtilization of Coal
1970-2000: Catalytic convertersPhase-out of Pb gasoline
1950-1970: Change from coal to oilPeak of Pb gasoline use
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Pettaquamscutt River Basin
1900 1925 1950 1975 2000
40
30
20
10
0
Year of Deposition
210Pb Model
1965 ± 1
40
30
20
10
0
0.0 0.2 0.4 0.6 0.8
1952 ± 1
1987 ± 1
137Cs (dpm.g-1)
Dep
th (c
m)
1800
1820
1840
1860
1880
1900
1920
1940
1960
1980
20000 100 200 300 400 500
Flux (ng cm-2 yr-1)
Year
of D
epos
ition
19301945
19601974
Sum of 15 parentPAH (excluding perylene)
1890
Down-core variations in PAH fluxes
29
Petrogenicsource ratio
Petrogenicsource ratio
Pyrogenicsource ratio
Pyrogenicsource ratio
1900
1920
1940
1960
1980
20000 1 2 3 4 5 6
mz 192 / phenanthrene
Year
of D
epos
ition
0 1 2 3 4 5
1900
1920
1940
1960
1980
2000
mz 216 / pyrene
Ratios from Gustafsson & Gschwend (1997)
Assessment of Pyrogenic vs Petrogenic PAH inputs based on molecular parameters
1800
1820
1840
1860
1880
1900
1920
1940
1960
1980
20000 2 4 6 8 10 12 14 16
Phenanthrene
Retene
Flux (ng cm-2 yr-1)
Year
of D
epos
ition
0 10 20 30 40 50