1. 3 rd GEOS-Chem Users’ Meeting April 12, 2007 Elsie Sunderland U.S. Environmental Protection Agency Office of Research & Development National Center for Environmental Research sunderland.elsie@epa.gov 3 rd GEOS-Chem Users’ Meeting April 12, 2007 Elsie Sunderland U.S. Environmental Protection Agency Office of Research & Development National Center for Environmental Research sunderland.elsie@epa.gov Atmosphere-Ocean Modeling Linkages

2. Primary Anthropogenic Emissions LAND ATMOSPHERE OCEAN recycling & terr. emission Hg(II) Hg(0) Hg(p) MeHg Net reduction Net Evasion methylation demethylation

3. EVASION ATMOSPHERIC DEPOSITION RIVERS LATERAL OCEAN FLOW RESERVOIR M w = C w V w MARINE BOUNDARY LAYER DEEP WATER FORMATION PARTICLE SETTLING Conceptual Model for Each Basin UPWELLING

4. Temporal Trends in Ocean Hg with GEOS-Chem Forecasted Deposition Source: Sunderland & Mason, 2007

5. Temporal Lag in Ocean Hg Enrichment Source: Sunderland & Mason, 2007

6. Estimated Fraction of Annual Hg Inputs Atlantic 35  S-55  N Pacific & Indian 40  S-30  N North Pacific >30  N Med. Sea 30-35  N

7. Recap: GEOS-Chem Surface Ocean Model Source: Strode et al., 2007 avg mixed depth = 53 m 1.9 15.516.6 22.8/yr 14.1/yr sorption reduction All units Mmol 0.06 pM 0.5 pM surface mixed layer thermocline atmosphere particle sinking entrainment diffusion upwelling entrainment upwelling diffusion entrainment upwelling HgT = 1.53 pM HgT = 1.06 pM

8. Model Improvements 1. Lateral Ocean Flow Source: Anderson, 2003

9. 2. Temporal Lag between Ocean Hg & Atmospheric Hg Source: IPCC/WMO/UNEP

10. Atlantic 35  S-55  N River Hg Discharge (Mmol/yr) Q (10 12 L/yr) N. Atlantic >55  N Atlantic 65  S-35  S Pacific & Indian 40  S-30  N N. Pacific >30  N Med. 30-35  N Antarctic >65  S Source: Dai & Trenberth, 2002; Sunderland & Mason, 2007 3. Riverine Discharges of Hg *compare: anthropogenic emissions ~ 12 Mmol/yr

11. 4. Methylmercury (MeHg) Speciation North Pacific Ocean 23-55  N Source: D. Krabbenhoft, USGS, unpublished data

12. Next Steps Historical anthropogenic emissions on a continental scale to estimate temporal responses of oceans Coupled pre-industrial deep ocean & GEOS- Chem models Expand surface “slab” model of ocean to include deep ocean waters Account for methylmercury speciation? Explore effects of climate change? Now Later