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).

Ancillary slides

CDOM : DOC relationships along a salinity gradient

Kennebec River and its estuary

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)

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

9

DOC versus salinity

DO

C (

mg

/l)

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?

0.4

0.5

0.6

0.7

0.8

0.9

1

0 2000 4000 6000 8000 10000 12000 14000 16000

Kennebec discharge versus ag550/salinity intercept

Discharge (ft3 s-1)

Zer

o in

terc

ept