Monitoring the Global Sea Level Rise Budget with Jason, Argo

and GRACE Observations

Eric Leuliette and Laury MillerNOAA/Laboratory for Satellite Altimetry

Ocean Climate Observation 7th Annual System Review • Silver Spring, Maryland • 27–29 October 2010

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Fourth levelFifth level

NOAA Jason Program

• NOAA CDR Program (NCDC)• NASA Measures Program • ESA Climate Change Initiative• SCOPE-CM (Operational meteorological agencies: EUMETSAT, NOAA, JMA, CMA)

Multiple agency efforts underway:

For practical purposes, the Ocean Surface Topography Science Team (OSTST), jointly led by NOAA, NASA, EUMETSAT & CNES, will be the focal point.

Sea Level Climate Data Records

4Ocean Climate Observation 7th Annual System Review • Silver Spring, Maryland• 27–29 October 2010

Iconic Climate Time Series Global Mean Sea Level Anomaly

CO2 at Mauna Loa

5Ocean Climate Observation 7th Annual System Review • Silver Spring, Maryland• 27–29 October 2010

The Challenge

?Ensemble mean steric sea level change (m), 2091-2100 wrt 1980-2000, from 12 AR4 models. (Yin et al., JCLIM, 2010)

TOPEX/Jason sea level trends (steric & eustatic) 1992 to 2010

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Sea Level BudgetSLtotal = SLsteric + SLmass

Total sea level• Tide gauge calibration shows offset November 2009• Trends in coastal/shallow water are significantly larger

than global sea level riseSteric sea level• Argo coverage and pressure sensor issuesOcean mass• Differences depending on processing center• Glacial isostatic adjustment models

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Tide gauge calibrationMitchum tide gauge calibration“Single mission” TX/J1/J2

combination calibration

Jason-2 ~1 cmoffset in

November 2009?

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Recent drift/offset in all altimeters

Apparent drifts/offsets in the altimeter — tide gauge residuals for Jason-1, Jason-2, and Envisat in late (November) 2009.

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No offset in Jason-2 sea levelJason-2 MSL residuals after removing trend, annual,

semi-annual, and 59-day terms

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Possible causes of offset/driftCommon to all altimeter calibrationsTide gauges• Instrument and datum shifts• Vertical land motion

Meteorological fields• Dry troposphere

• Inverted barometer correction is not applied for calibration

Reference frame

Independent causes• Wet troposphere

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Earthquakes near gaugesTwo relatively large earthquakes struck near gauges at roughly the

time of the offset• M 8.1, Samoa, 29 September 2009• M 7.3, 100 km, Suva, Fiji, 9 November 2009• M 6.8, 135 km, Nuku'Alofa, Tonga, 24 November 2009.

GPS vertical motion at Pago Pago

SOPAC GPS vertical solutions for Pago Pago show large post-seismic motion opposite of the long-term trend

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Contributions to offset from gaugesContribution to Jason-2 offset from individual tide gauges• weighted differences in mean bias for Nov. 2009 ± 5 months

Pago Pago

The offset is seen by the entire tide gauge

network

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Trends in sea level20th century rate of sea level rise: 1.7 ± 0.3 mm/yrRate during altimetry era (1992–2010): 3.3 ± 0.4 mm/yr

• (when corrected for GIA effect of +0.3 mm/year)

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Sea level rise near coastsSince 2002 coastal sea level rise has been significantly

larger than global

Trends from 2005.5 to 2010.5• Complete Jason coverage area: 2.6 mm/year• > 120m depth 2.3 mm/year (sealevel.colorado.edu)• > 200 km from the coast 1.9 mm/year (Leuliette & Miller 2009)

Trends 2005 – 2010.5 Trends versus distance

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Ocean mass: geoid changeOcean mass variations observed directly from GRACE have little trend for

2004 – 2010.

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)

• Published results differ more than forcing uncertainty (~20%)

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Peltier (2004, 2009)+1.9 mm/year

Paulson et al. (2007), Tamisiea (2010)+1.0 mm/year

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Budget results

Trend (mm/year)

Steric (Argo) 0.6 ± 0.4

Mass (GRACE, Paulson GIA) 0.9 ± 0.3

Mass (GRACE, Peltier GIA) 1.8 ± 0.3

Steric + mass (Paulson GIA) 1.5 ± 0.4

Steric + mass (Peltier GIA) 2.4 ± 0.4

Total sea level (Jason-1/2) 1.6 ± 0.8

Trends for Components of Sea Level Rise and Total Sea Level (2004 – 2010.25)

17Ocean Climate Observation 7th Annual System Review • Silver Spring, Maryland• 27–29 October 2010

DiscussionWhile the 6-year “global” budget can be closed within 90%

confidence intervals, “global” excludes > 66°, < 200 km from coasts, and > 900 m depth (Argo)

Total sea level• Tide gauge calibration issue needs to be resolved to ensure the integrity of the

sea level CDR

Steric sea level• Global analyses are preliminary until pressure drift issues are resolved

Ocean mass• Consensus on GIA correction: Paulson, et al. (2007) and Tamisiea (2010) are

appropriate for ocean mass trends• NASA has included the rapid follow-on to GRACE in its budget for a start in

FY2011 with launch by 2016• Heavily focused on maintaining data continuity from GRACE and minimizing any data

gap after GRACE.