Aeolian transport in the McMurdo Dry Valleys (MCM), AntarcticaAeolian processes = wind generated...
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This work was supported by: NSF OPP-0432595 NSF MCB-0237335 NSF OPP-0631494 ● MCM: driest (< 10 cm y -1 ) and coldest (mean -20°C) desert on Earth; end member ecosystem in the LTER network ● Largest relatively ice-free area in Antarctica ● Landscape of the MCM: mosaic of permanently ice-covered lakes , ephemeral streams , exposed soils and glaciers ● Biology of each of these landscape units is dominated by microorganisms ● Constant and often strong winds distribute material among the landscape units 2. Aeolian Sediment Characteristics 2. Aeolian Sediment Characteristics A A =aeolian material L L=lake ice sediment G G=glacier ice sediment C=cryoconite S S=soil 3. Aeolian Fluxes 3. Aeolian Fluxes Background Background 4. TV 4. TV Stoichiometry Stoichiometry Redfield ratio proportion of elements equals to 106 atoms C per 16 atoms of N per 6 atoms of P Katabatic winds originate from the cooling of air atop the Polar Plateau. The cold dense air then flows downhill, warming adiabatically as it descends. 1. Aeolian Transport in Taylor Valley (TV) 1. Aeolian Transport in Taylor Valley (TV) 100 µm At FRX sediment flux does not change with elevation At HOR sediment flux is greatest at the lowest elevation site At BON sediment flux is the greatest at the highest elevation Elevation, distance from the lake mean ± SD (1999-2008) Sediment traps F1 F2 F3 F4 F5 F6 F7 F8 F9 Aeolian Flux (g.m -2 .y -1 ) 0 500 1000 1500 2000 2500 3000 FRX FRX mean ± SD (1999-2008) Sediment traps H1 H2 H3 H4 H5 H6 H7 H8 H9 Aeolian Flux (g m -2 y -1 ) 0 1000 2000 3000 4000 5000 6000 7000 Elevation, distance from the lake HOR HOR mean ± SD (1999-2008) Sediment traps B1 B2 B3 B4 B5 B6 B7 B8 B9 Aeolian Flux (g m -2 y -1 ) 0 10 20 30 40 50 60 Elevation, distance from the lake BON BON Flux of sediment within Flux of sediment within FRX FRX , , HOR HOR and and BON BON Flux of POC, PON and POP within Flux of POC, PON and POP within FRX FRX , , HOR HOR and and BON BON between 1999-2008 between 1999-2008 97.8% (±2.15%) of the aeolian material is coarse sand (particles > 250 µm) Lower water, organic matter, POC, PON and POP content than other sediments Higher pH than lake ice, glacier ice and cryoconite sediment; similar to soils Most material is transported during katabatic winds from SSW (from the continent toward the Ross sea) and partially from NE (from the ocean inland) during sporadic low pressure events Aeolian transport in the McMurdo Dry Valleys (MCM), Antarctica Aeolian transport in the McMurdo Dry Valleys (MCM), Antarctica Marie Šabacká 1 , John C. Priscu 1 , Hassan Basagic 2 , Andrew G. Fountain 2 & Mark C. Greenwood 3 1 Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA, 59717 2 Department of Geology, Portland State University, Portland, OR, USA, 97207 3 Department of Mathematical Sciences, Montana State University, Bozeman, MT, USA, 59717 contacts: [email protected], [email protected] Hypotheses Hypotheses Given the relatively low and seasonal growth rates observed for the microorganisms within MCM, their overall distribution should be controlled to a large degree by the physical environment Aeolian transport during strong katabatic winds is the primary dispersive agent of microorganisms and associated organic matter among the MCM landscape units primary site of research in MCM Taylor Valley Measured using Sensit™ acoustic wind eroding mass sensor installed in the upper (BON), middle (HOR) and lower parts (FRX) of TV As particles hit the crystal, a fixed charge of kinetic energy is produced, which correlates to mass flux H11B Sediment transport at a given location is greater (p<0.001, H=1374.8) near the soil surface (20 cm) than higher above the ground (100 cm) Sensits 20 and 100 cm 0 2000 4000 6000 8000 Sensits 20 and 100 cm 0 2000 4000 6000 8000 Sensits 20 and 100 cm 0 2000 4000 6000 8000 Particle flux (counts 15 min -1 ) 8000 0 FRX FRX BON BON at at 20 cm 20 cm Particle flux at at 100 cm 100 cm Sensit 2008/09 0 2000 4000 6000 8000 Sensit 2008/09 0 2000 4000 6000 8000 Sensit 2008/09 0 2000 4000 6000 8000 Particle flux Particle flux (counts 15 min -1 ) 8000 0 HOR HOR FRX FRX BON BON Upper Valley (BON) has the greatest (p<0.001, H=1475.1) amounts of aeolian material transported through the air P ar t i c l e f l u x ( c o u n t s 1 5 m i n - 1 ) Wind Direction (°) Wind Speed (m s -1 ) BON BON N Ross Sea Antarctic Ice Shelf Taylor Valley BON BON HOR HOR FRX FRX POC A L G C S mg C g -1 0.0 0.2 0.4 0.6 0.8 1.0 1.2 PON A L G C S mg N g -1 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 POP A L G C S mg P g -1 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 water content A L G C S % 0 2 4 6 8 10 12 organic matter A L G C S % dw 0.0 0.5 1.0 1.5 2.0 2.5 pH A L G C S 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Collected from sediment traps installed at BON, HOR and FRX of TV Aeolian processes = wind generated processes POC flux (mg m -2 y -1 ) 0 50 100 150 200 p= 0.023 H = 7.567 PON flux (mg m -2 y -1 ) 0 2 4 6 8 10 12 14 p= 0.11 H = 4.412 Kruskal-Wallis One Way Analysis of Variance on Ranks POP flux (mg m -2 y -1 ) 0 2 4 6 8 p = 0.059 H = 6.664 POC POC PON PON POP POP BON BON BON HOR HOR HOR FRX FRX FRX Based on the amount of material collected from sediment traps installed at BON, HOR and FRX of TV and sampled yearly from 1999-2008 Mean ±SD On average the sediment flux is greatest in the medium part of the valley (HOR) P (μ mol mg -1 ) 0.0 0.5 1.0 1.5 2.0 2.5 N (μ mo mg -1 ) 0.0 0.5 1.0 1.5 2.0 2.5 A (aeolian sediment) L (lake ice sediment) G (glacier ice sediment) C (cryoconite) S (soil) Bonney area Redfield ratio (16:1) N (μ mol mg -1 ) 0.0 0.5 1.0 1.5 2.0 2.5 C (μ mol mg -1 ) 0 2 4 6 8 10 12 14 16 A (aeolian sediment) L (lake ice sediment) G (glacier ice sediment) C (cryoconite) S (soil) Refield ratio (6.6:1) P (μ mol mg -1 ) 0 10 20 30 N ( μ mol mg -1 ) 0 50 100 150 200 250 300 BON 11.9±15.8 FRX 20.3±26.9 RI 42.9 Redfield ratio (16:1) P (μ mol mg -1 ) 0 5 10 15 20 25 N (μ mol mg -1 ) 0 100 200 300 400 BON 9.5±5.3 FRX 22.3±10 HOR 22.5±6 WV 24.8±18 Redfield ratio (16:1) N:P (molar) N:P (molar) N (μ mol mg -1 ) 0 100 200 300 C ( μ mol mg -1 ) 0 1000 2000 3000 4000 5000 BON 10.4±2.1 FRX 18.9±8.0 WV 7.8 RI 10.1 Redfield ration (6.6:1) N (μ mol mg -1 ) 0 100 200 300 400 500 600 C ( μ mol mg -1 ) 0 1000 2000 3000 4000 5000 BON 15.9±6.5 FRX 13.5±5.5 HOR 23.6±2.9 WV 8.6±4.5 Redfield ratio (6.6:1) C:N (molar) C:N (molar) Lake mats Lake mats Lake mats Lake mats Stream mats Stream mats Stream Stream mats mats Sediments Sediments Sediments Sediments Lake ice and stream mats in Taylor Valley have C:N and N:P ratios similar to or higher than the Redfield ratio suggesting a balance growth Aeolian sediment , lake ice and glacier ice sediment, cryoconites and soil have C:N ratios close to the Redfield. N:P ratios vary greatly among different habitats and localities and are generally bellow the Redfield ratios suggesting N or P defficiency Conclusions Conclusions 1. Aeolian transport in Taylor Valley Most material is transported down-valley from Taylor glacier towards the Ross Sea during katabatic events when the wind speed reaches above 10 m s -1 . Sediment is predominantly transported near the soil surface. 2. Aeolian sediment The material transported via wind is physically and chemically similar to nearby soils. It is slightly alkaline (~ 8.6), has a very coarse texture (98% of particles > 250 μm), very low water content (< 2%) and organic matter content (<1%). 3. Aeolian fluxes Over the past decade, on average, most aeolian material have been collected from sediment traps located in the middle part (HOR)of the TV 4. Basic stoichiometry C:N:P ratios suggest balance growth within lake ice and stream mats while the sediments are N or P deficient Direction of major particle flux in Taylor Valley
Transcript of Aeolian transport in the McMurdo Dry Valleys (MCM), AntarcticaAeolian processes = wind generated...
This work was supported by:
NSF OPP-0432595NSF MCB-0237335NSF OPP-0631494
● MCM: driest (< 10 cm y-1) and coldest (mean -20°C) desert on Earth; end member ecosystem in the LTER network
● Largest relatively ice-free area in Antarctica● Landscape of the MCM: mosaic of permanently ice-covered lakes, ephemeral
streams, exposed soils and glaciers ● Biology of each of these landscape units is dominated by microorganisms● Constant and often strong winds distribute material
among the landscape units
2. Aeolian Sediment Characteristics2. Aeolian Sediment Characteristics
AA =aeolian material LL=lake ice sediment GG=glacier ice sedimentC=cryoconite SS=soil
3. Aeolian Fluxes 3. Aeolian Fluxes
Background Background
4. TV4. TVStoichiometryStoichiometry
Redfield ratio proportion of elements equals to 106 atoms C per 16 atoms of N per 6 atoms of P
Katabatic winds originate from the cooling of air atop the Polar Plateau. The cold dense air then flows downhill, warming adiabatically as it descends.
1. Aeolian Transport in Taylor Valley (TV)1. Aeolian Transport in Taylor Valley (TV)
100 µm
At FRX sediment flux does not change with elevation
At HOR sediment flux is greatest at the lowest elevation site
At BON sediment flux is the greatest at the highest elevation Elevation, distance from the lake
mean ± SD (1999-2008)
Sediment traps
F1 F2 F3 F4 F5 F6 F7 F8 F9
Aeol
ian
Flux
(g.m
-2.y
-1)
0
500
1000
1500
2000
2500
3000
FRXFRX
mean ± SD (1999-2008)
Sediment traps
H1 H2 H3 H4 H5 H6 H7 H8 H9
Aeol
ian
Flux
(g m
-2 y-1
)
0
1000
2000
3000
4000
5000
6000
7000
Elevation, distance from the lake
HORHORmean ± SD (1999-2008)
Sediment traps
B1 B2 B3 B4 B5 B6 B7 B8 B9
Aeol
ian
Flux
(g m
-2 y-1
)
0
10
20
30
40
50
60
Elevation, distance from the lake
BONBON
Flux of sediment within Flux of sediment within FRXFRX, , HORHOR and and BONBON
Flux of POC, PON and POP within Flux of POC, PON and POP within FRXFRX, , HORHOR and and BONBON between 1999-2008 between 1999-2008
97.8% (±2.15%) of the aeolian material is coarse sand (particles > 250 µm)
Lower water, organic matter, POC, PON and POP content than other sediments
Higher pH than lake ice, glacier ice and cryoconite sediment; similar to soils
Most material is transported during katabatic winds from SSW (from the continent toward the Ross sea) and partially from NE (from the ocean inland) during sporadic low pressure events
Aeolian transport in the McMurdo Dry Valleys (MCM), AntarcticaAeolian transport in the McMurdo Dry Valleys (MCM), Antarctica
Marie Šabacká1, John C. Priscu1, Hassan Basagic2, Andrew G. Fountain2 & Mark C. Greenwood3
1Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA, 597172Department of Geology, Portland State University, Portland, OR, USA, 972073Department of Mathematical Sciences, Montana State University, Bozeman, MT, USA, 59717
contacts: [email protected], [email protected]
HypothesesHypothesesGiven the relatively low and seasonal
growth rates observed for the microorganisms within MCM, their
overall distribution should be controlled to a large degree by the
physical environment
Aeolian transport during strong katabatic winds is the primary
dispersive agent of microorganisms and associated organic matter
among the MCM landscape units
primary site of research in MCM
Taylor Valley
Measured using Sensit™ acoustic wind eroding mass sensor installed in the upper (BON), middle (HOR) and lower parts (FRX) of TV
As particles hit the crystal, a fixed charge of kinetic energy is produced, which correlates to mass flux
H11B
Sediment transport at a given location is greater (p<0.001, H=1374.8) near the soil surface (20 cm) than higher above the ground (100 cm)
Sensits 20 and 100 cm
F6 Sens 20 07
F6 Sens 100 07
F6 Sens 20 08
F6 Sens 100 08
B Rig Sen 20 07
B Rig Sen 100 07
B Rig Sen 20 08
B Rig Sen 100 08
Sensit
0
2000
4000
6000
8000Sensits 20 and 100 cm
F6 Sens 20 07
F6 Sens 100 07
F6 Sens 20 08
F6 Sens 100 08
B Rig Sen 20 07
B Rig Sen 100 07
B Rig Sen 20 08
B Rig Sen 100 08
Sensit
0
2000
4000
6000
8000Sensits 20 and 100 cm
F6 Sens 20 07
F6 Sens 100 07
F6 Sens 20 08
F6 Sens 100 08
B Rig Sen 20 07
B Rig Sen 100 07
B Rig Sen 20 08
B Rig Sen 100 08
Sensit
0
2000
4000
6000
8000
Parti
cle
flux
(co
unts
15
min
-1)
8000
0
FRXFRX BONBON
atat 20 cm 20 cm
Particle flux
atat 100 cm100 cm
Sensit 2008/09
F6 Sens 20 07
F6 Sens 20 08
FRX Sensit 07
HOR Sens 08
BON Sensit 07
BON Sens 08
B Rig Sen 20 07
B Rig Sen 20 08
Sensit
0
2000
4000
6000
8000Sensit 2008/09
F6 Sens 20 07
F6 Sens 20 08
FRX Sensit 07
HOR Sens 08
BON Sensit 07
BON Sens 08
B Rig Sen 20 07
B Rig Sen 20 08
Sensit
0
2000
4000
6000
8000Sensit 2008/09
F6 Sens 20 07
F6 Sens 20 08
FRX Sensit 07
HOR Sens 08
BON Sensit 07
BON Sens 08
B Rig Sen 20 07
B Rig Sen 20 08
Sensit
0
2000
4000
6000
8000Particle flux
Parti
cle
flux
(co
unts
15
min
-1)
8000
0
HORHORFRXFRX BONBON
Upper Valley (BON) has the greatest (p<0.001, H=1475.1) amounts of aeolian material transported through the air
Parti
cle
flux
(co
unts
15
min
-1)
Wind Direction (°) Win
d Sp
eed
(m s
-1 )
BONBON
N
Ross Sea
Antarctic Ice Shelf
Taylor Valley
BONBONHORHOR
FRXFRX
POC
A L G C S
mg
C g
-1
0.0
0.2
0.4
0.6
0.8
1.0
1.2PON
A L G C S
mg
N g
-1
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16 POP
A L G C S
mg
P g-1
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
water content
A L G C S
%
0
2
4
6
8
10
12 organic matter
A L G C S
% d
w
0.0
0.5
1.0
1.5
2.0
2.5 pH
A L G C S7.0
7.5
8.0
8.5
9.0
9.5
10.0
Collected from sediment traps installed at BON, HOR and FRX of TV
Aeolian processes = wind generated processes
POC
flux
(mg
m-2
y-1)
0
50
100
150
200
p= 0.023H = 7.567
PON
flux
(mg
m-2
y-1)
0
2
4
6
8
10
12
14 p= 0.11H = 4.412
Kruskal-Wallis One Way Analysis of Variance on Ranks
POP
flux
(mg
m-2
y-1)
0
2
4
6
8p = 0.059H = 6.664POCPOC PONPON POPPOP
BONBON BON
HORHORHOR
FRXFRXFRX
Based on the amount of material collected from sediment traps installed at BON, HOR and FRX of TV and sampled yearly from 1999-2008
Mean ±SD
On average the sediment flux is greatest in the medium part of the valley (HOR)
P (µ mol mg-1)0.0 0.5 1.0 1.5 2.0 2.5
N (µ
mo
mg-
1 )
0.0
0.5
1.0
1.5
2.0
2.5A (aeolian sediment)L (lake ice sediment)G (glacier ice sediment)C (cryoconite)S (soil)Bonney areaRedfield ratio (16:1)
N (µ mol mg-1)
0.0 0.5 1.0 1.5 2.0 2.5
C (µ
mol
mg-
1 )
0
2
4
6
8
10
12
14
16
A (aeolian sediment)L (lake ice sediment)G (glacier ice sediment)C (cryoconite)S (soil)Refield ratio (6.6:1)
P (µ mol mg-1)0 10 20 30
N (µ
mol
mg-
1 )
0
50
100
150
200
250
300
BON 11.9±15.8FRX 20.3±26.9RI 42.9Redfield ratio (16:1)
P (µ mol mg-1)0 5 10 15 20 25
N (µ
mol
mg-
1 )
0
100
200
300
400
BON 9.5±5.3FRX 22.3±10HOR 22.5±6WV 24.8±18Redfield ratio (16:1)
N:P (molar)N:P (molar)
N (µ mol mg-1)
0 100 200 300
C (µ
mol
mg
-1)
0
1000
2000
3000
4000
5000
BON 10.4±2.1FRX 18.9±8.0WV 7.8RI 10.1Redfield ration (6.6:1)
N (µ mol mg-1)0 100 200 300 400 500 600
C (µ
mol
mg
-1)
0
1000
2000
3000
4000
5000
BON 15.9±6.5FRX 13.5±5.5HOR 23.6±2.9WV 8.6±4.5Redfield ratio (6.6:1)
C:N (molar)C:N (molar)Lake matsLake mats Lake matsLake mats
Stream matsStream mats Stream Stream matsmats
SedimentsSediments
SedimentsSediments
Lake ice and stream mats in Taylor Valley have C:N and N:P ratios similar to or higher than the Redfield ratio suggesting a balance growth
Aeolian sediment, lake ice and glacier ice sediment, cryoconites and soil have C:N ratios close to the Redfield. N:P ratios vary greatly among different habitats and localities and are generally bellow the Redfield ratios suggesting N or P defficiency
ConclusionsConclusions1. Aeolian transport in Taylor Valley
Most material is transported down-valley from Taylor glacier towards the Ross Sea during katabatic events when the wind speed reaches above 10 m s-1 . Sediment is predominantly transported near the soil surface.
2. Aeolian sedimentThe material transported via wind is physically and chemically similar to nearby soils. It is slightly alkaline (~ 8.6), has a very coarse texture (98% of particles > 250 μm), very low water content (< 2%) and organic matter content (<1%).
3. Aeolian fluxesOver the past decade, on average, most aeolian material have been collected from sediment traps located in the middle part (HOR)of the TV
4. Basic stoichiometryC:N:P ratios suggest balance growth within lake ice and stream mats while the sediments are N or P deficient
Direction of major particle flux in Taylor Valley
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