Post on 06-Aug-2021
Methane and other trace gases: NIWA measurements
Keith Lassey
NIWA, Wellington, New Zealand.(k.lassey@niwa.co.nz)
Asia-Pacific Workshop on Carbon-Cycle ObservationsNIES, Tsukuba, Japan, 17–19 March 2008
on behalf of: Tony Bromley, Ross Martin, Gordon Brailsford, Rowena Moss, Kim Currie, Bill Allan, Dave Lowe
Trace gas sampling programme
• Baseline levels of trace gases at Baring Head, Wellington:
CO2 (since 1972), CH4 (since 1989), CO (since 1989), N2O (since 1996), O2/N2 (since 1999)13C, 14C in above, and 18O in some of above
• Baseline levels of some gases/isotopes at Scott Base, Antarctica
• Trace gases/isotopes in shipboard air samples (NZ to Japan), since May 2004
• pCO2 , etc, in sub-Antarctic surface water
41°S
Baring Head
Baring Head
Wellington
Nelson
Baring Head CO2
• monitoring commenced in Dec 1972 in cooperation with C.D. Keeling, Scripps
• measured continuously in situ by NDIR
• longest-running continuous station in SH, next longest in world after Mauna Loa
• inter-calibrated with Scripps & NOAA
• complemented in 1998 by δ13C measurements (continuous flow: D. F. Ferretti)
• complemented in 1999 by O2 measurements (paramagnetic analyser: A. C. Manning)
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
310
320
330
340
350
360
370
380
390
CO
2 (p
pm)
Mauna LoaBaring Head
Baring Head & Mauna Loa CO2
Acknowledgement: Scripps Institution of Oceanography
Features (SH vs NH):• Much smaller seasonal amplitude
(more demands on precision) due to less biosphere in SH
• Lower [CO2 ] due to NH-dominated anthropogenic sources
Baring Head CO2
• Dataset largely under-utilised in global carbon-cycle studies
• Data (not just CO2 ) submitted to World Data Centre for Greenhouse Gases (Tokyo)
• Reported strongly in IPCC 4th Assessment Report (Dave Lowe, Lead Author, Chapter 2)
• Data used in recent study of the Southern Ocean as a CO2 sink [Le Quéré et al., 2007]
Le Quéré, C. et al. (2007). Science 316: 1735–1738.
Baring Head 14CO2
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
-100
010
020
030
040
050
060
070
0
Δ14C
O2
(pm
C)
“Bomb-14C pulse”
Baring Head Δ14CO2
• Visionary commencement of measurements, pre-dating the “bomb-14C pulse”
• Near-unique and valuable dataset:long-term evolution of Δ14CO2 critical to carbon-dating calibration [eg, Hua & Barbetti, 2004]
response of C reservoirs to bomb-14C injection pivotal to understanding C-cycling [eg, Lassey et al., 1996; Peacock, 2004]
Hua, Q.; Barbetti, M. (2004). Radiocarbon 46: 1273–1298.Lassey, K.R. et al. (1996). Tellus 48B: 487–501.Peacock, S. (2004). GBC 18: GB2022,
pCO2 time series along a sub-Antarctic surface transect
STF
SAF
SASW
Subtropical water
SASWMay SSTs
Attribution: Work of Kim Currie et al.transect
pCO2 time series along a sub-Antarctic surface transect
SASW
‘Munida’ time series since 1998, led by Kim Currie
Measurements of:• temperature• salinity• pCO2• pH• alkalinity• etcbi-monthly since 1998
RV Polaris (Munida replacement)
⎟⎠⎞
⎜⎝⎛ −
+=365
3172sin1.23.10 tT π
SASW Seasonal Cycles
⎟⎠⎞
⎜⎝⎛ −
+=365
1562sin103552tpCO π
⎟⎠⎞
⎜⎝⎛ −
+=365
1382sin9.12.123tNO π
6
8
10
12
14
16
1998 1999 2000 2001 2002 2003 2004 2005
Tsw
/ oC
3 20
3 30
3 40
3 50
3 60
3 70
3 80
19 9 8 19 9 9 2 0 0 0 2 0 0 1 2 00 2 20 0 3 20 0 4 2 0 0 5
pCO
2 / Η
atm
7.75
7.8
7.85
7.9
7.95
8
1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
pH (2
5 oC
)
02468
101214161820
1998 1999 2000 2001 2002 2003 2004 2005
[NO
3] /
mm
ol m
-3
⎟⎠⎞
⎜⎝⎛ −
+=365
1622sin05.0869.7 tpH π
No
indi
catio
n of
a tr
end!
SASW Air-Sea flux of CO2SASW C O 2
330
340
350
360
370
380
Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05
pC O 2swpC O 2air
SASW Flux and �pCO2
-10-8-6-4-2024
Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05-60
-40
-20
0
20
40
60fluxDpCO2
ΔpCO2
Baring Head CH4 and δ13C(CH4 )
• monitoring of δ13C(CH4 ) commenced in 1987; [CH4 ] commenced in 1989
• [CH4 ] measured by GC/FID, δ13C(CH4 ) by IRMS, on grab samples
• inter-calibrated with recognised standards
• [CH4 ] complements NOAA record; δ13C(CH4 ) arguably the best record globally
Baring Head CH4
1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Year
1650
1670
1690
1710
1730
1750
1770
CH
4 (p
pb)
CH4 plateaued?
CH4 rising again?
CH4 mini-plateau?
Baring Head δ13C(CH4 )
1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Year
-47.
5-4
7.4
-47.
3-4
7.2
-47.
1-4
7-4
6.9
-46.
8-4
6.7
δ13C
H4
(‰)
what happened here?
CH4 “stable”?
An important chlorine sink for CH4 ?
• Upper plot:composite seasonality of [CH4]
• Centre plotcomposite seasonality of δ13CH4
• Lower plot:[CH4] vs δ13CH4: “phase ellipse”Slope of ellipse axis determined by isotope fractionation in sinkDash-dot line corresponds to ‘accepted’ fractionation of 5.4‰Actual slope ⇒ fraction’n ~13‰
Allan, W. et al. (2001). GBC 15: 467-481.Allan, W. et al. (2007). JGR 112: D04306.
Source: Allan et al. (2001)
An important chlorine sink for CH4 ?
• Why is sink fractionation as high as ~13‰? (OH sink has fractionation ~5.4‰ or less)
• Likely answer: role by active Cl (fractionation ~60‰)
• Allan et al. (2007) argue that a Cl sink that removes 13–37 TgCH4 /yr globally can account for observations
• Cl sink absent from current global budgets
Allan, W. et al. (2001). GBC 15: 467-481.Allan, W. et al. (2007). JGR 112: D04306.
Source: Allan et al. (2001)
Ship voyages, Nelson (NZ) to Osaka
Shipboard measurements
• transect: 41.3°S, 174.3°E to 34.7°N, 135.5°E • 8 voyages on two bulk-carrier vessels*, May
2004 to May 2007• collect dried air samples every 2.5° between
latitudes –20° to +20°, every 5° elsewhere• record meteorology at time of sampling• analyse samples in NIWA laboratory for:
CH4, 13CH4, CO, 13CO, 14CO, C18O
• measure real-time CN densities• 24-hr particulate aerosols (hi-vol filtration)
* Vessels Fujitrans World then Transfuture 5, Toyofuji Shipping Company Ltd, Nagoya
Shipboard CO• Inter-comparisons of CO:
3 voyages, Dec – early Jan4 voyages in May (but CO unavailable for May 2007)
• approx. NH seasonality:peak ~150ppb in Martrough ~90 ppb in Aug
• approx. SH seasonality:peak ~60ppb in Septrough ~40 ppb in Feb
• Note inter-annual variability north of ~10°S
CO Dec Jan
0
50
100
150
200
-32 -24 -16 -8 0 8 16 24 32
Dec 04 Dec 05 Jan 07
CO May
0
50
100
150
200
-32 -24 -16 -8 0 8 16 24 32
May 04 May 05 May 06
Shipboard CH4 and δ13C(CH4 )
CH4 Dec Jan
1700
1720
1740
1760
1780
1800
1820
1840
1860
1880
1900
-32 -24 -16 -8 0 8 16 24 32
Dec 04 Dec 05 Jan 07
CH4 May
1700
1720
1740
1760
1780
1800
1820
1840
1860
1880
1900
-32 -24 -16 -8 0 8 16 24 32
May04 May05 May 06 May07
13CH4 Dec Jan
-47.5
-47.4
-47.3
-47.2
-47.1
-47
-46.9
-32 -24 -16 -8 0 8 16 24 32
Dec 04 Dec 05 Jan 07
13CH4 May
-47.5
-47.4
-47.3
-47.2
-47.1
-47
-46.9
-32 -24 -16 -8 0 8 16 24 32
May04 May05 May 06 May 07
Why the NZ focus on CH4 ?The NZ GHG emission inventory (shown for 2004):• approx 50% CO2 , 50% agricultural GHGs
— highest ag. component of all developed countries• 2/3 of ag. GHGs are CH4 from ruminant livestock• ruminant CH4 has no known abatement prospects
SF60.03%
PFCs0.12%
HFCs0.80%N2O
17.2%
CO245.6%
CH436.2%
Acknowledgements
• NIWA colleagues, both past and present, for their foresight and skill
• Logistical and technical support from NIES (Prof. Yukihiro Nojiri et al.)
• Opportunities, facilities and hospitality aboard vessels of Toyofuji Shipping Company Ltd
• Funding: NZ Foundation for Research, Science & Technology
• Co-funding: NOAA GCOS programme
Thank you