A Global Observing System for Monitoring and Prediction of Sea Level Change Lee-Lueng Fu COSPAR, 2014, Moscow Jet Propulsion Laboratory California Institute of Technology

Evolution of Earth Observation from Space : Exploration Weather satellites (TIROS, Nimbus, NOAA series, Meteor, Meteosat,…) Land imaging (Landsat, SPOT, …) Ocean observations (Seasat, Geosat,..) Advanced measurement (UARS, T/P, ERS, …) : Earth System Science EOS (Terra, Aqua, Aura) Envisat, TRMM A-Train (Cloudsat, Calipso, GCOM-W, etc)

The Bretherton Diagram set the stage of Earth System Science

The A-Train example of an observing system The satellites are in a polar orbit, crossing the equator northbound at about 1:30 p.m. local time, within seconds to minutes of each other.

Earth System Science Approach to the Sea Level Problem gravimetry scatterometry In-situ lidarInSAR Reference frame altimetry River discharge Adapted from Church et al (2013)

Understand the processes Regional variability Assessment and projection Calibration and continuity Challenges IPCC AR5

Nerem et al, 2013 Altimetric record of the global mean sea level

Global sea level change in terms of ocean heat and ice melt Llovel et al., 2014 altimetry GRACE Altimetry –GRACE Argo

Altimetry: 2.8 +/- 0.4 mm/yr The dominant error is tide gauge calibration owing to land motions. The time scale is much longer than decadal. GRACE: 2.0 +/- 0.4 mm/yr The dominant error is due to GIA correction with time scale much longer than decadal. When calculating the rate change on decadal time scale, the long time scale errors are canceled, leading to 0.07 mm/yr for altimetry and 0.1 mm/yr for GRACE. This allows detection of rate change of sea level of 0.28 mm/yr/decade and the rate change of the mass component of 0.4 mm/yr/decade, at 95% confidence. Detection of the rate change of global mean sea level

The standard error for the full-depth steric sea level rate is sqrt( ), or 0.12 mm/yr, comparable to the error estimated from Argo for the upper 2000 m (0.15 mm/yr) This allows detection of rate change of steric sea level of 0.24 mm/yr/decade at 68% confidence, or 0.48 mm/yr/decade, ~50% of the signal, at 95 % confidence. The rate of steric sea level can be related to the rate of ocean heat storage: α = coefficient of thermal expansion c p =specific heat at constant pressure; q’=heat content anomaly/unit volume If the warming is concentrated at the surface layer, then Q’= ocean warming rate at W/m 2 Steric sea level and ocean warming

Willis et al (2011) Regional variability: small long-term trends imbedded in large cyclic natural variability

Hamlington et al., 2013 Decadal Sea Level Change in the Pacific Ocean

The Effects of the Pacific Decadal Oscillation Hamlington et al., 2013

The length of time (in years) required for determining the trend of sea level change with an accuracy of 1 mm/yr. from 5 (deep blue) to 100 years (deep red). Hughes and Williams, 2011

Slangen et al (2011) A projection of sea level change from 2000 to 2100

CRYOSAT-2 Europe Complementary Missions - Medium Accuracy/Higher Inclination HY-2B China Reference Missions - Higher Accuracy/Medium Inclination Jason-2 Europe/USA Launch Date Jason-3 Europe/USA Proposed Approved Operating Sentinel-3C/D Sentinel-3B Europe SWOT USA/France Jason-CS Europe/USA Sentinel-3A Europe sw 24may11 GLOBAL ALTIMETER MISSIONS SARAL/AltiKa France/India HY-2A

cm Cross calibration between TOPEX/Poseidon and Jason-1 SSH Difference Before After Bonnefond and Haines, 2008

Conclusions Among the suite of space-borne Earth observations, a system of measurements emerge to form an observing system for monitoring global sea level change. The system allows the separation of the effect of ocean heat from that of melting ice, providing key information for estimating future sea level change and ocean warming. The system provides cross-cutting information in oceanography, glaciology, meteorology, and geodesy to close the budget of sea level change. International science teams have been established to assimilate the observations for making projection of future sea level change. altimetry InSAR Geodesy Modeling Scientists & engineers Argo