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Spatial variability in drainage basin DOC fluxes : Is there a relationship to remotely-
sensed measurements?
Joe Salisbury (UNH)
Jacqui Aitkenhead-Peterson (UNH)
Janet Campbell (UNH)
L. David Meeker (UNH)
Frank Muller-Karger (USF)
Charlie Vorosmarty (UNH)
0 10 20 300
0.5
1
1.5
2
Kennebec: m = -0.017
0 10 20 300
0.5
1
1.5
2
Penobscot: m = -0.040
Ab
so
rpti
on
@ 5
50
nm
. (m
-1)
Salinity (psu)
Advertised title: Coastal river plumes in the Gulf of Maine: Linking salinity vs. absorption relationships to terrestrial DOC fluxes
Outline:
1. Drainage basin plume identification
2. DOC flux model
3. Previous work with NEGOM data
4. Salinity – CDOM relationships in the Gulf of Maine
5. Relationship to drainage basin DOC fluxes
D i s c h a r g e/ s e d
T i m e s e r i e s o f o c e a n c o l o r m e a s u r e m e n t s a t l o c a t i o n A ( r e d ) a n d M i s s i s s i p p i d i s c h a r g e ( b l u e ) ( S c a l e d v a l u e s )
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
S e p - 9 7 A p r - 9 8 N o v - 9 8 M a y - 9 9 D e c - 9 9 J u n - 0 0 J a n - 0 1
0 . 1 0 . 3 0 . 70 . 5N o d a t a M a p p e d c o r r e l a t i o n ( r ) v a l u e s w e e k l y a v e r a g e d d a t a
L o c a t i o n A
S a l i s b u r y e t a l . 2 0 0 2 , S u b m i t t e d t o D S R
Aitkenhead-McDowell DOC flux model
- relates soil C:N ratio to DOC flux (kg hectare-1 year-1)
- Biome-based
0 20 40 60 80
Mississippi
Pearl
Appalachicola
Suwannee
Pascagoula
Escambia
Choctawatchee
DOC Export (kg ha-1 yr-1)
Predicted
Observed
Results for several rivers entering the northern Gulf of Mexico
DOC Index – The Aitkenhead-McDowell modeled flux divided by climatological runoff.
Same units as concentration (mg l-1) Perhaps similar to average concentration
ag443 vs. salinity within individual plumes (NEGOM-3) 11-13-89 to 11-25-98
Right – rescaled for detail
0 2 4 6 8 10 12 14 16-0.12
-0.1
-0.08
-0.06
-0.04
-0.02
0
Slope of ag vs. salinity relationship plotted against DOC index
slope
DOC index (g m-3)
0 10 20 300
0.5
1
1.5
2Androscoggin: m = -0.027
0 10 20 300
0.5
1
1.5
2Chandler: m = -0.053
0 10 20 300
2
4
6Crescent: m = -0.170
0 10 20 300
0.5
1
1.5
2Kennebec: m = -0.017
0 10 20 300
0.5
1
1.5
2Penobscot: m = -0.040
0 10 20 300
0.5
1
1.5
2Presumpscot: m = -0.008
0 10 20 300
0.5
1
1.5
2StCroix: m = -0.014
0 10 20 300
0.5
1
1.5
2Saco: m = -0.013
0 10 20 300
0.5
1
1.5
2Union: m = -0.019
Ab
sorp
tio
n @
550
nm
. (m
-1)
Salinity (psu)
Salinity versus CDOM absorption @550nm for 9 Maine Rivers
0 1 2 3 4 5 6 7 8 9 100
0.01
0.02
0.03
0.04
0.05
0.06
Slope of absorption - salinity versus average DOC concentration (@ 0 Salinity)
Endmember DOC concentration (mg/liter)
Slo
pe
(*-1
)
R2 = 0.63
Slope of ag_salinity versus basin C:N ratio
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
15 17 19 21 23 25 27 29
C:N ratio
Slo
pe
of
ag_s
alin
ity
Conclusions:
1. Relationships between ag and salinity appear to be local
2. The slope of this relationship is often related to the DOC endmember concentration and its proxy – the DOC index
Why we’re continuing work on this :
Hope to develop localized algorithms that would enable the retrieval of surface DOC concentration via remotely sensed data
The endThis work was supported by NASA's Office of Earth Sciences through a grant entitled "A satellite-based system for monitoring biogeochemical fluxes between the continental land mass and the coastal ocean" (NAG5-12451, C. Vorosmarty, P.I.), and by the NOAA Coastal Services Center through an award to the UNH Center for Coastal Ocean Observation and Analysis (COOA). (NOAA award NA16OC2740).
0 5 10 15 20 25 300
0.5
1
1.5
2
2.5
3
3.5
4
CDOM absorption versus salinity
abso
rpti
on
@44
0 (1
/m)
Salinity (psu)
-5 0 5 10 15 20 25 30 350
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Colored dissolved organic carbon absorption versus salinity
CD
OM
1/m
Salinity (psu)
Linear model
Mean, range and standard deviation for 5 psu bins
End member
-5 0 5 10 15 20 25 30 350
1
2
3
4
5
6
7
8
9Dissolved organic carbon versus salinity
DO
C (
mg
/l)
Salinity (psu)
-5 0 5 10 15 20 25 30 35-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
(ag443:carbon – end member ag443:carbon) versus salinity
ag44
3:ca
rbo
n -
en
dm
emb
er a
g44
3:ca
rbo
n
Salinity (psu)
-5 0 5 10 15 20 25 30 350
1
2
3
4
5
6
7
8
9Dissolved organic carbon versus salinity
DO
C (m
g/l)
Salinity (psu)0 5 10 15 20 25 30
0
1
2
3
4
5
6
7
8Dissolved organic carbon versus salinity (modeled)
DO
C (
mg
/l)
Salinity (psu)
conservative mixing model
3rd order polynomial (good fit)
0 5 10 15 20 25 300
5
10
15
20
25
30
35
Cumulative carbon loss (percent) along the salinity gradient
DO
C (
mg
/l)
Salinity (psu)
Conservative mixing line value = 0%
0 5 10 15 20 25 300
10
20
30
40
50
60
70
80
90
Total DOC removal across a salinity gradient
pe
rce
nt
DO
C c
on
ce
ntr
ati
on
re
du
cti
on
Salinity (psu)
0 5 10 15 20 25 30-0.05
0
0.05
0.1
0.15
0.2
0.25
Rate of carbon removal (mg/l C per psu)
DO
C (
mg
/l)
Salinity (psu)
Absorption @555nm versus salinity
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5 10 15 20 25 30
Salinity (psu)
Ab
so
rpti
on
@5
55
nm
(1
/m)
log [DOC] versus Salinity
0.3
0.5
0.7
0.9
1.1
1.3
0 5 10 15 20 25 30Salinity (psu)
log
[DO
C]
log [DOC] versus Salinity
0.6
0.7
0.8
0.9
1
1.1
1.2
0 5 10 15 20 25 30
Salinity (psu)
log
[D
OC
]
absorption @555nm versus Salinity
0.5
1
1.5
2
2.5
0 5 10 15 20 25 30
Salinity (psu)
ab
so
rpti
on
@ 5
55n
m
(1/m
)Salinity versus absorption (left) and [DOC] (right)
Kennebec
Penobscot
Union
absorption @555nm versus salinity
00.10.2
0.30.40.50.6
0.70.80.9
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Salinity
abso
rpti
on
(m
-1)
DOC versus salinity
0
1
2
3
4
5
6
7
8
9
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Salinity (psu)
DO
C (
mg
l-1
)
no data 0.3 0.4 0.5 0.6 0.7
0 2 4 6 8 10 12 14 16 180
200
400
600
800
1000
1200
Wind speed m s-1
Remote determination of ROFI – (covariance technique)January - March, 1999
no data 0.3 0.4 0.5 0.6 0.7
0 2 4 6 8 10 12 14 16 180
200
400
600
800
1000
1200
Wind speed m s-1
Covariance Technique July-September, 1999
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2ag550 versus salinity (best fit lines) for 7 cruises - Kennebec River
Salinity (psu)
bes
t fi
t in
terc
ept
Seasonality?