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402401400399398397
CO2, ppm
2487912461
110
108
206
231
162
164
490
14
12
10
8
6
4
2
0
Altitu
de
, km
-620 -600 -580 -560 -540
O2, per meg
2387912356
108
94
178
176
133
148
409
605040302010
CO, ppb
1996910447
89
92
178
195
121
139
378
VOC Observations over the Southern Ocean during ORCAS
Rebecca Hornbrook1,*, Eric Apel1, Nicola Blake2, Alan Hills1, Elliot Atlas3, Britton Stephens1, Colm Sweeney4, Eric Kort5, Martin Hoeker-Martinez5, and the ORCAS science team
1NCAR, Boulder, CO; 2University of California, Irvine, CA; 3University of Miami, Miami, FL; 4NOAA, Boulder, CO; 5University of Michigan, Ann Arbor, MI; *rsh@ucar.edu;
Overview The NCAR/NSF G-V O2/N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS) took place in Jan-Feb 2016 and was based in Punta Arenas, Chile. The primary goal of the study was to investigate the air-sea exchange of O2 and CO2 over the Southern Ocean where the uptake of anthropogenic carbon is a key process that is poorly represented by models.
In addition to many long-lived gases, measurements of reactive volatile organic compounds (VOCs) were measured using the Trace Organic Gas Analyzer (TOGA) and advanced whole air canisters (AWAS), and are used to better understand and constrain air-sea exchange in the southern ocean region.
VOC tracers from several sources/types:
• Biogenic VOCs and oxidation products • Anthropogenic VOCs • Oil and Gas Tracers • Long-lived Halogenated VOCs • Short-lived Halogenated VOCs • OVOCs, including HCHO • DMS • Alkyl Nitrates • Biomass burning tracers (HCN, CH3CN)
TOGA The NCAR Trace Organic Gas Analyzer is a fast online gas chromatograph/ mass spectrometer (GC/MS) that makes simultaneous measurements of 50+ VOCs every 2 minutes.
Summary The air over the Southern Ocean is extremely clean, with very low mixing ratios of anthropogenic VOCs, and indications of losses of soluble OVOCs and nitriles to the ocean surface. CHBr3 and CH2Br2 are correlated with O2 emissions from the Southern Ocean, suggesting a common source with similar enhanced atmospheric lifetimes. DMS is not correlated with O2, however, and emissions of DMS decreased significantly between January and February.
2.094
Jan Feb
Figure 1. ORCAS flights during January and February 2016, overlaid on the monthly average chlorophyll concentrations from AQUA/MODIS. (AQUA/MODIS imagery produced by the Earth Observatory Group in coordination with Gene Feldman and Norman Kuring, NASA Goddard Ocean Color Group.)
25201510
CH2Cl2, pptv
9822326
9
4
3
127497839
58
43
54
18
3
138
1311
41
47
121
146
123
137
350 High O2
Mid O2
Low O2
6420
Benzene, pptv
9822326
9
4
3
127497839
58
43
54
18
3
27410314490
135
132
269
278
217
229
522
High O2
Mid O2
Low O2
200150100500
CH3CN, pptv
9521296
9
4
3
116467439
58
43
54
18
3
138
1311
41
47
121
146
123
137
350
High O2
Mid O2
Low O2
200150100500
DMS, pptv
9822326
9
4
3
127497839
58
43
54
18
3
15131524
53
59
156
191
172
193
400
High O2
Mid O2
Low O2
1.21.00.80.60.40.20.0
CH3I, pptv
9822326
9
4
3
127497839
58
43
54
18
3
138
1311
41
47
121
146
123
137
350
High O2
Mid O2
Low O2
3.02.01.00.0
CHBr3, pptv
9822326
9
4
3
127497839
58
43
53
18
3
138
1311
41
47
120
145
122
137
338
High O2
Mid O2
Low O2
14
12
10
8
6
4
2
0
Altitu
de
, km
3002001000
CH3COCH3, pptv
9822326
9
4
3
127497839
58
43
52
18
3
138
1311
41
47
120
142
122
137
348 High O2
Mid O2
Low O2
14
12
10
8
6
4
2
0
Altitu
de
, km
1.61.20.8
CH2Br2, pptv
9619294
6
117507537
59
43
52
17
198
1714
38
49
122
142
105
131
336
High O2
Mid O2
Low O2
VOC correlations with O2
Figure 4. VOCs observed over oceans binned by altitude and O2 (high O2>-540 per meg>mid O2>-560 per meg>low O2.) Several ocean-emitted halogenated VOCs were correlated with O2 in the marine boundary layer (MBL) and mid-troposphere (CH2Br2, CHBr3 and CH3I). DMS was not correlated with O2 in the MBL, but was slightly correlated with O2 in the mid-troposphere, consistent with air more recently in the MBL. Several OVOCs and nitriles were anti-correlated with O2 in the MBL and mid-troposphere (e.g., acetone, CH3CN), consistent with more polluted air having less ocean influence, while less-soluble anthropogenic species (e.g., benzene, CH2Cl2) were not correlated with O2 in the lower troposphere.
VOC correlations with CO2 and CO
Figure 5. Observed VOCs binned by altitude and CO2 and CO (high CO2>399 ppm>low CO2; high CO>43 ppb>low CO). CH2Br2 and CHBr3 were anti-correlated with CO2 in MBL and mid-troposphere, while CH3I was correlated with CO2 in the MBL. This is due to elevated CH3I west of Chile, where CO2 is elevated (see Fig. 6). Several OVOCs and nitriles were correlated with CO2 and CO in the MBL and mid-troposphere (e.g., acetone, CH3CN), suggesting losses to the ocean surface. Less soluble anthropogenic species (e.g., CH2Cl2, benzene) and DMS have no clear correlation with CO2 in the lower troposphere, although benzene is correlated with CO, even at very low benzene mixing ratios, consistent with elevated SH CO.
Figure 6. Observed mixing ratios of selected VOCs and CO2, sized by altitude.
-90 -80 -70 -60 -50
Longitude
1.2
1.0
0.8
0.6
0.4
0.2
CH
3 I, pptv
-90 -80 -70 -60 -50
Longitude
402
401
400
399
398
397
396
395
CO
2 , ppm
-70
-60
-50
-40
La
titu
de
-90 -80 -70 -60 -50
Longitude
5
4
3
2
1
CH
Br3 , p
ptv
-90 -80 -70 -60 -50
Longitude
300
250
200
150
100
50
0
DM
S, p
ptv
ORCAS Flights
Transport of VOCs from NH to SH Figure 3. From several Jan-Feb studies over the Pacific/Southern Ocean (TORERO 2012; CONTRAST 2014, ORCAS 2016), composites of VOCs from -75°S to 40°N show significant interhemispheric differences, and indicate transport pathways from the NH and tropics to the SH. Longer-lived CH2Cl2 is transported from the NH to the SH via the UTLS, while CH3COCH3 and CH3OH are transported to high southern latitudes via the mid-troposphere from the tropics.
806040200
pptv CH2Cl216
14
12
10
8
6
4
2
0
Altitu
de
, km
2.52.01.51.00.50.0pptv
C2Cl4161284
pptv CHCl3
16
14
12
10
8
6
4
2
0
Altitu
de
, km
-60 -40 -20 0 20 40
Latitude
50403020100
pptv Benzene
-60 -40 -20 0 20 40
Latitude
8004000
pptv CH3COCH3
-60 -40 -20 0 20 40
Latitude
10000
pptvCH3OH
Figure 2. Observed O2, CO2 and CO from the ORCAS project, binned by altitude. Shown on each plot as box and whiskers are the median, 10th, 25th, 75th and 90th percentiles of these data from a TOGA time base merge, with the number of data points in each bin shown on the plots.
O2, CO2, CO
14
12
10
8
6
4
2
0
Altitu
de
, km
1.41.21.00.80.6
CH2Br2, pptv
149
1720
52
69
181
208
135
45
169
2347010741
58
39
22
15
104
259
High CO2
Low CO2
14
12
10
8
6
4
2
0
Altitu
de
, km
3002001000
CH3COCH3, pptv
149
1720
52
69
178
205
134
45
169
2347010741
58
39
22
15
104
256 High CO2
Low CO2
1601208040
CH3CN, pptv
149
1720
52
69
180
208
135
45
167
222669941
57
38
22
15
104
259
High CO2
Low CO2
43210
Benzene, pptv
149
1720
52
69
180
207
134
44
167
2347010741
58
39
22
15
104
258
High CO2
Low CO2
3.02.01.00.0
CHBr3, pptv
149
1720
52
69
180
207
134
45
165
2347010741
58
39
21
15
104
248
High CO2
Low CO2
1.20.80.40.0
CH3I, pptv
149
1720
52
69
181
208
135
45
169
2347010741
58
39
22
15
104
259
High CO2
Low CO2
300200100
CH3COCH3, pptv
63203122
44
56
142
145
90
22
60
135497325
45
36
31
29
21
106
270 High CO Low CO
43210
Benzene, pptv
63203122
44
56
145
147
90
21
60
135497325
45
36
31
29
21
106
271
High CO Low CO
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