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An interdisciplinary study of land-sea carbon coupling between the Penobscot River and Gulf of Maine William M. Balch & Collin Roesler- Bigelow Laboratory.

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Presentation on theme: "An interdisciplinary study of land-sea carbon coupling between the Penobscot River and Gulf of Maine William M. Balch & Collin Roesler- Bigelow Laboratory."— Presentation transcript:

1 An interdisciplinary study of land-sea carbon coupling between the Penobscot River and Gulf of Maine William M. Balch & Collin Roesler- Bigelow Laboratory Andrew Barnard, WET Labs Thomas G. Huntington, USGS, Augusta, ME Huijie Xue, University of Maine Orono George R. Aiken, USGS Boulder, CO

2 Acknowledgements Respective lab groups –Dave Drapeau, Bruce Bowler, Emily Booth, Laura Windecker, Heidi Franklin, Rois Langner, Dan Abraham, Kenna Butler, Yi Du NASA IDS

3 Overview Introduce the study area Follow DOC from watershed to coastal sea Discuss quantity and quality of DOC Optical proxies for using remote sensing to estimate DOC concentrations 3-D circulation modeling results Summarize

4 In a recent paper on the Gulf of Maine’s optical properties, we showed that the Gulf is “CaseII- dissolved” all the time and “Case II particulate” about half the time…

5 The DOC “Tea Bag” Analogy Soil build-up of particulate organic carbon/leaf litter during growing season- “the tea leaves” Precipitation soaks POC- “the steep” DOC is extracted- “the brew” Transformations enroute- “binds to other POC, mineral surfaces (i.e. stains your teeth), is metabolized (digested)” Remaining DOC is carried downstream to the ocean…some of which is visible, some not, but it is a large pool!

6 But the plot thickens… There are different ways to brew your tea The downstream ocean has its own source of DOC (some of which is colored) Which DOC dominates in river-impacted coastal waters? What is the fate of the terrestrial vs marine DOC? (…fundamental to the Case II vs Case I distinction)

7 The birth of terrestrially impacted, Case II-dissolved water…We start way upstream in the Penobscot River…    West Enfield

8 Penobscot River empties into Penobscot Bay…

9 Penobscot Bay then empties into the Gulf of Maine

10 Are the tributaries of the Penobscot equal in their DOC concentration? …but beware, the West Branch has a dam!

11 “When you brew your tea is everything…” “Summer tea” “Iced tea”

12 Timing is everything… Jan-May Frozen ground Fast runoff does not penetrate frozen sediments…poor “steep” Temperature does affect the leaching cold water “bad brew” June-December End of growing season with lots of accumulated carbon Runoff percolates in earth…good “steep” Warm temperatures enhance microbial breakdown of leaf litter, “good steep”, “good brew”

13 Put daily discharge, measured DOC concentration as function of flow rate & time of year, one can model the daily DOC flux…

14 Optical proxies for DOC in the river…fluorescence of DOC

15 Penobscot River-seasonally variable relationship between discharge and CDOM fluorescence… CDOM Fluor (ppb QS) Discharge (cfs) Eddington CDOM fluor Discharge W. Enfield

16 CDOM Excitation/Emission fluorescence spectra vary with land use… Pleasant River Agricultural watershed Passadumkeag Wetland Ex (nm) Em (nm) Ex (nm)

17 Ex/Em properties vary with the watershed… Different Penobscot Watersheds % Aerial Coverage Wetland peak ratio (Ex/Em 265/475 : 225/430) F (QS eq) EX200:EM300 Agri

18 In line ferry data from Penobscot Bay… strong inverse relation between a pg425 and salinity Salinity a pg425 S a

19 How much of the DOC that makes it down the river, through the bay and into the Gulf of Maine? First two years of our IDS study we were very lucky: – Dry year – 2005 THE wettest year on record Allowed a good contrast in the quantity and quality of the DOC that came out into the Gulf of Maine

20 How much does the [DOC] change from Penobscot Bay to the Gulf of Maine? River outfall Bay WMCC Ext EMCC Gulf of Maine Gradual decline Through the Bay

21 How does the quality of the DOC change from Bay to Gulf? River outfall Bay WMCC Ext EMCC Gulf of Maine BIG TRANSITION AT BAY EXIT TO GOM { SUVA (10 -3 m 2 mgDOC -1 ; 254nm) Sargasso

22 Space time plot for DOC in the Gulf of Maine Solstice ‘05 ‘04 Wet Dry Portland, MEYarmouth, NS

23 SUVA (DOC specific absorption cross section) x10 -3 m 2 (mg DOC) -1 Solstice ‘05 ‘04 Wet Dry Portland, MEYarmouth, NS Sargasso Value=0.8 Strong EW gradient

24 Going back 8 years with a gp412 …2004 and 2005 indeed were extraordinary years… ‘05 ‘04 ‘03 ‘02 ‘01 ’00 ’99 ‘98 Portland, MEYarmouth, NS Wettest Dry Usually saw elevated values in SS water coming from Gulf of St Lawrence Clear influence of Maine rivers Since 2004, elevated SS CDOM has not been seen! Unprecedented input of CDOM from Maine rivers

25 They were extraordinary years for optical scattering, too… ‘05 ‘04 ‘03 ‘02 ‘01 ’00 ’99 ‘98 Portland, MEYarmouth, NS Wettest Dry Maine’s driest year on record!

26 Aqua estimates at the mouth of Penobscot Bay X X P<0.001 X X DOC in upper tributaries

27 We have combined the DOC Export along with 3d circulation model of H. Xue to model the DOC distribution

28 It is clear that in the Gulf of Maine, transformations are occurring in CDOM plotted against salinity…

29 Summary The relation between discharge rate and DOC concentration shows two different relationships, a winter-spring and summer-fall pattern The fluorescence properties of CDOM provide information on watershed type DOC quantity drops gradually from the upper watershed through Penobscot Bay DOC quality (SUVA) is high throughout the Penn Bay and drops dramatically as water exits into the GoM suggesting a loss in aromaticity

30 Summary During dry year (’04) and wet year (’05) no influence of Gulf of St. Lawrence water entering GOM and affecting CaseII dissolved conditions. Dry year (’04) showed major loss of CDOM in mid Gulf…photooxidation? Aqua-derived DOC values look reasonable Clear evidence of nonconservative CDOM behavior in the Gulf Have modeled 3-D DOC flow. Future plans to incorporate DOC non-conservative transformations

31 Thank you!

32

33 How do three of the biggest watersheds compare in the concentration of their DOC (tea)?


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