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Closing the Global Sea Level Rise Budget with GRACE, Argo, and Altimetry Observations

Closing the Global Sea Level Rise Budget with GRACE, Argo, and Altimetry Observations. Presented by Eric Leuliette. Requirement, Science, and Benefit. Requirement/Objective Mission Goal: Research the rate and causes and of global sea level rise Science ( contribution to meeting requirement)

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Closing the Global Sea Level Rise Budget with GRACE, Argo, and Altimetry Observations

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  1. Closing the Global Sea Level Rise Budget with GRACE, Argo, and Altimetry Observations Presented by Eric Leuliette

  2. Requirement, Science, and Benefit Requirement/Objective • Mission Goal: • Research the rate and causes and of global sea level rise Science(contribution to meeting requirement) • Can the observational sea level rise budget be closed? Benefit • Intergovernmental Panel on Climate Change • Sea level • Global heat budget • Science Teams • Ocean Surface Topography • Argo Science Team • GRACE Science Team

  3. Sea level budget The equation for the sea level budget may be expressed as SLtotal = SLsteric + SLmass SLtotalis total sea level Altimeters: Jason-1, Jason-2, and Envisat SLstericis the steric component of sea level Argo (for the upper layer) SLmass is the ocean mass component GRACE + geocenter + oblateness All fields are processed at STAR

  4. A problem closing the budget? Willis et al. [2008] failed to close the sea level rise budget using a combination of Argo, GRACE, and Jason-1 data Suggested possible systematic errors in the observing systems. Willis et al. [2008] Total sea level

  5. Total sea level from altimetry • STAR supports the development of the Radar Altimeter Database System (RADS) • World’s leading platform for sea level climate data records (CDRs) • Includes latest correction products • Supports STAR’s Cal/Val activities • – Intermission • – Tide gauge • Sea level rise research • – Leuliette and Miller [2009]

  6. Building a climate data record: calibration • Calibration is critical for CDRs. • STAR supports Mitchum (USF) in calibrating altimeters with a global tide gauge network. STAR contributes to the Ocean Surface Topography Science Team cal/val efforts. Jason-1 and Jason-2 special issues Leuliette et al. 2004 Leuliette et al. 2010

  7. STAR steric sea level analysis from Argo STAR produced monthly fields of steric sea level variations using a method that removed WOCE climatology before interpolation Trends in steric sea level 2004 – 2008 The budget analysis in Leuliette and Miller [2009] excluded 2003 because of poor coverage of the Southern Hemisphere

  8. STAR GRACE processing Peltier (2004,2009) Unpublished (Proudman) STAR processes GRACE gravity fields into ocean mass variations • Ocean mass variations observed directly from GRACE have little trend for 2004–2009. • A complete analysis must account for ocean mass changes “masked” by geoid variations from the solid Earth’s response to ice melt since the last ice age (Glacial Isostatic Adjustment, GIA) • Uncertainty in ice sheet history, 20% (?) • Published results differ more than forcing uncertainty

  9. GIA corrections • Uncertainties in the GIA correction is the largest source of error in the observation sea level rise budget • GIA models agree that accounting for GIA changes in altimetry observations adds +0.3 to +0.5 mm/year to globalsea level rise. • The disagreement is amplified for global ocean mass. • – Paulson et al. (2007): +1.0 mm/year • – Peltier (2004, 2009): +1.9 mm/year • STAR is collaborating with solid earth geophysicists to improve GIA models • Horton (University of Pennsylvania) • Tamisiea (Proudman Oceanographic Institute)

  10. Closing the budget Leuliette and Miller [2009] Blue lines: Direct observations Red lines: Inferred from budget equation SLtotal = SLsteric + SLmass

  11. Conclusion: Closing the budget • With our analysis, we can close the sea level rise budget for the period of 2004 to 2009.25. • Demonstrates that the three observation systems can be used for cross-calibration.

  12. Challenges and Path Forward • Continuing science challenges • Argo instrument biases and sampling issues • Variations in glacial isostatic adjustment models • GRACE lifetime and follow-on • Next steps • Basin/regional analyses and impact of Greenland ice melt • Extending time series to the entire altimetry era to understand evolution of sea level contributions • Path into applications/operations • Contribute to the IPCC and sea level community

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