Continental Coastal Interactions: Assessing carbon inventories and fluxes in watersheds, inland waters, and associated coastal margins: data sources and gaps David Butman, Jeremy Mathis, Rob Striegl

Goals:• Present current estimates of carbon flux

through aquatic and coastal systems.• Highlight uncertainties and data gaps in

aquatic and coastal carbon cycle research.• Improve communication between the

terrestrial, aquatic, and coastal carbon cycle science communities.

Conterminous US Aquatic Carbon Totals (outward flux)

Process Areal Fluxg C m2 yr-1

Total FluxTg-C yr-1

Lateral Export (to coasts) 5.5 41-49Lakes and Reservoirs (to atmosphere)

~1.6 11-14

Streams and Rivers (to atmosphere)

14.5 73

Aquatic Burial (Lakes and Resevoirs)

~-2.4 -1.2

Total C flux 17-20 ~130

Terrestrial Forest NEP - observation/process based:19-21 g C m2 yr-1 (150-160 Tg C yr-1) Williams et al in prep (Jeff Masek Plenary)

Inversion models predict higher terrestrial sink

Uncertainties and Data Needs

• Common definitions of spatial domains, inland vs. estuarine vs coastal systems – (Terrestrial and Aquatic Communities).

• Spatial data – lake areas, river surface areas, seasonal changes in area, wetland areas, inundation frequency and extent.

• Observational Data – monitoring efforts must be maintained and improved, coastal (head of tide) chemical and flow data, wetland carbon observations.

Questions raised:

• How can we constrain uncertainties in aquatic flux estimates?• What are the sources of aquatic carbon and are these scale dependent?• Are the Great Lakes a net source or sink of CO2?• What are the effects of sea level rise on the mobilization of coastal carbon?• Can organic carbon export support the observed increase in pCO2 in the

Bering Sea?• What efforts are underway to quantify permafrost contributions to aquatic

carbon export?• Does the export of inorganic carbon as both DIC and pCO2 matter in

terrestrial carbon accounting? • Can we improve our understanding both spatially and temporally of sources

of aquatic and coastal carbon?• What is the role of disturbance and events (flooding, drought, hurricanes)

on the aquatic and coastal carbon cycles)• Can we further refine the understanding of estuaries as sources of CO2 and

continental shelves as sinks of CO2?

Moving forward:

• Continue to expand the community of aquatic and coastal carbon cycle scientists.– Seek Canadian and Mexican counterparts for NACP and OCB

efforts• Increase and support efforts to measure aquatic and

coastal carbon – (burial and atmospheric connections in particular).

• Work to resolve temporally the inland aquatic carbon flux.• Continue to push for collaborative efforts to link the

terrestrial and aquatic communities (NACP, OCB, cross disciplinary funding opportunities).

• Attend today’s breakout session on terrestrial-aquatic-coastal carbon cycling integration.