Observations and Coupled Terrestrial-Coastal Ocean Modeling of Carbon-Cycle Exchange in the Mississippi-Atchafalaya

Basin and Northern Gulf of MexicoSteven Lohrenz (U. Mass Dartmouth)

Wei-Jun Cai (U. Georgia)Hanqin Tian (Auburn)

Ruoying He (N. Carolina State U.)Zuo Xue (N. Carolina State U.)

Katja Fennel (Dalhousie)Charles Hopkinson (U. Georgia)

Stephan Howden (U. Southern Miss.)

Acknowledgements• Project is funded through the NASA

Interdisciplinary Research in Earth Sciences and the NASA Carbon Monitoring System programs

• Additional funding, data and cruise support provided by NSF, NOAA, EPA, and USGS

Overview• Introduction

– Coupled models for the study of carbon dynamics in complex systems– Uncertainties in coastal carbon budgets– Current projects:

• NASA IDS: Coupled Terrestrial-Ocean Models - A Case Study in the Gulf of Mexico• Carbon Monitoring System Projects: Phase 1 and Phase 2

• Approach– Descriptions of the models

• Dynamic Land Ecosystem Model• Coastal Ocean Biogeochemical Model

– Model integration• Results to Date

– Data development – Model refinement and validation– Integration of terrestrial and ocean models

• Next Steps

Introduction: Coupled modeling approaches to examine carbon dynamics in complex systems

• Current research in carbon cycle science often focuses on specific subsystems (e.g., ocean, forest, tundra, urban, etc.)

• However, interactions among subsystems can lead to nonlinear relationships in their response to changes in external forcing

• Such interactions complicate efforts to predict how systems will behave and may produce unintended consequences for carbon management efforts

Introduction: Uncertainties in Coastal Carbon Budgets

• Carbon fluxes in the coastal margins remain poorly constrained in global carbon budgets

• Large uncertainties remain particularly in the temporal and spatial patterns of variability

• Reductions in uncertainties as well as ability to project changes in carbon fluxes in response to climate- and human-related activities will benefit carbon management efforts

P. Coble

Najjar presentation and numerous posters by Cai, Herrmann, Friedrichs, Alin, Signorini, Wang, Vlahos, and others

NASA IDS Project - Coupled Terrestrial-Ocean Models: A Case Study in the Gulf of Mexico

• Changing climate and land use practices can dramatically alter hydrologic and biogeochemical processes in terrestrial environments

• Such changes influence the delivery of water, carbon and nutrients into rivers, estuaries, and coastal ocean waters

• Here, we use the Mississippi River watershed and northern Gulf of Mexico as a case study to illustrate linkages between terrestrial and ocean ecosystems

NASA Carbon Monitoring System Projects

• Phase 1: Estimation of land ocean atmosphere carbon fluxes ‐ ‐and exchanges in the Mississippi River– Land-ocean C and nutrient fluxes– Coastal margin air-sea C exchange– Coastal to open ocean C exchange

• Phase 2: Development of observational tools and coupled models of land-ocean-atmospheric fluxes and exchanges in the Mississippi River watershed and Gulf of Mexico in support of carbon monitoring– Advances the Phase 1 effort by using coupled terrestrial and ocean

models– Develop geo-referenced products– Estimate uncertainties

Approach: Coupled Terrestrial-Ocean Models

Dynamic Land Ecosystem Model used to estimate spatial and temporal patterns of delivery of water, carbon, and nitrogen and compared to data-based observations

DLEM terrestrial outputs linked to a physical-biogeochemical model to characterize coastal carbon fluxes and ecosystem dynamics

Modeling efforts will be supported by field survey-based and satellite-based observations of carbon fluxes and other biogeochemical processes

Tian et al., 2010a,b; Tian et al.,2011, Tian et al.,2012

Hoffman et al., Ann. Rev., 2011;Fennel et al., 2011 and in prep.

Hyun and He (2010); Xue et al. in prep

Approach

Approach: Dynamic Land Ecosystem Model

Tian et al., 2010a,b; Tian et al.,2011, Tian et al.,2012, Tao et al. 2013Dynamic Land-Ecosystem Model (DLEM2.0) See Tian et al., poster 241, Tuesday

Conceptual Model of DLEM

Coupling of biogeochemical and hydrological cycles (C,N,P,H2O) in DLEM

See Tian et al., poster 241, Tuesday

NASA IDS Terrestrial Domain: Mississippi-Atchafalaya Basin

• The drainage basin for the Mississippi-Atchafalaya river system covers 41% of the conterminous U.S.

• Among the ten largest rivers in the world with respect to water and sediment discharge and the largest in the North American continent

Temperate or sub-polar needleleaf forest

Tropical or sub-tropical broadleaf evergreen

Temperate or sub-polar broadleaf deciduous

Mixed Forest

Temperate or sub-polar shrubland

Temperate or sub-polar grassland

Sub-polar or polar grassland-lichen-moss

Wetland

Cropland

Barren Lands

Urban and Built-up

Water

Tian et al.

Approach: SABGOM

Hoffman et al., Ann. Rev., 2011;Fennel et al., 2011 and in prep.See He et al., poster 242, Tuesday

Spatial and temporal patterns of cropland in the Mississippi-Atchafalaya River Basin during 1901-2008 (Tian et al.)

Results to Date

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Crop

are

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2005

• Assemble terrestrial data sets for model input

– Land cover– Historical and

projected climate– Land use– Disturbance and

regrowth– Manure/fertilizer– Population data

Results to Date• Model refinement and validation

Comparison of simulated (blue line) and observed (red dots) total inorganic carbon in the vicinity of the Mississippi River outflow region Xue et al. in prep

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expo

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Raymon and Cole,2003 (MRB)

See Tian et al., poster 241, Tuesday

DLEM-simulated total N export (DIN+DON+PON) driven by land use/cover change (LUCC, including land management), climate change and all the environmental changes

Relative contributions from LUCC and climate

Tian et al.

Results to Date

DLEM simulated (a) Dissolved Inorganic Nitrogen (DIN, NO3+NH4) and (b) Dissolved Inorganic Carbon (DIC) input from the Mississippi-Atchafalaya River Basin system in the first decade of the 20th and 21st centuries

See He et al., poster 242, Tuesday

Higher DIN in recent decade due to population growth and land use practices

Results to Date• Data set development: extensive ship-based observations in the

northern Gulf of Mexico region from 2003 - 2012Jun 24-31 2003 R/V Pelican

Aug 1-8 2004 R/V Pelican

Oct 3-7 2005 R/V Pelican

Apr 27 - May 1 2006 R/V Pelican

Jun 6-11 2006 OSV Bold (EPA)

Sep 6-11 2006 OSV Bold (EPA)

Jul 10 - Aug 4 2007 R/V Brown (NOAA)

May 1-8 2008 R/V Pelican

31 Oct-7 Nov 2008 R/V Pelican

Jan 8-20 2009 R/V Cape Hatteras

Apr 19 - May 1 2009 R/V Cape Hatteras

July 18 - 30 2009 R/V Cape Hatteras

Oct 28 - Nov 9 2009 R/V Sharp

Mar 11-21 2010 R/V Cape Hatteras

Jul 21 – Aug 13 2012 R/V Ronald H. Brown www.gulfcarbon.org

• Huang et al., 2012, Biogeosci. and in review• Guo et al., 2012, Limnol. Oceanogr.• Cai et al., 2011, Nature Geosci.• Cai et al., 2011, Ann. Rev. Mar. Sci.• Two Ph.D. dissertations, other papers in prep.

Results to Date

Model refinement and validation

Positions (red dots) of in situ observations and three sub-regions (near field, intermediate, and far field) where area-mean time series comparisons were made. Also shown is 50 m isobath

See He et al., poster 242, Tuesday

Model refinement and validation

Time series comparisons between observed (red) and simulated (blue) NO3 and chlorophyll in three sub-regions of the northern Gulf

See He et al., poster 242, Tuesday

Model refinement and validation

Comparison between simulated (left) and observed (right) seasonal mean surface Chl-a concentration

See He et al., poster 242, Tuesday

See He et al., poster 242, Tuesday

Next Steps

• Temperature and precipitation under high (A2) and low (B1) emissions scenarios

• These data will provide inputs to the land ecosystem model

• Outputs include freshwater discharge and export of carbon and nitrogen, which feed into coastal model

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A2_precipitation

B1_precipitation

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Next Steps

• Develop both hindcasts (1900-1910, 2000-2010) and forecasts (2090-2100)

• Examine sensitivity to different drivers:– Climate (temperature, precipitation, solar radiation, relative humidity)– Land cover change– Land management including nitrogen fertilizer use, irrigation– Atmospheric CO2 concentration– Atmospheric nitrogen deposition– Tropospheric ozone pollution

• For forecasts, use two IPCC climate scenarios (A2, B1) including different land use scenarios, freshwater, and nutrient loading climate projections

Future Applications

LandCarbon Management

Land Use PracticesWater and Forest Management

Agriculture, FertilizerGHGs

Energy and BiofuelsDevelopment

Ocean Carbon ReservoirLong term Sequestration

of Carbon?

Coastal MarginAir-sea flux of CO2

Nutrients and HypoxiaOcean Acidification

Wetlands LossCoastal Restoration

Water QualityFisheries Habitat

Sea Level RiseRiver Export

Export

• Model development will provide decision support for issues related to carbon management, water quality, and ecosystem sustainability

Thank you!

www.gulfcarbon.org