1. Global Interannual Upper Ocean Heat Content Variability Gregory C. Johnson (NOAA/PMEL), John M. Lyman (UH/JIMA & NOAA/PMEL), Josh K. Willis (NASA/JPL), Sydney Levitus (NOAA/NODC), Claudia Schmid (NOAA/AOML), & Gustavo Goni (NOAA/AOML) Estimate Annual Average Upper Ocean Heat Content –In situ data (XBTs, Argo floats, CTDs, autonomous pinnipeds, etc.) –Satellite altimetry (Aviso weekly merged delayed-mode maps) Can combine in situ & altimetry data (e.g. Willis et al., 2004) Can also use altimetry for in situ error estimates –Subsample 13 years like a single years in situ distribution –Map subsampled years & compare to fully resolved fields Recent Decrease in global average upper ocean heat content –Significant Where has the upper ocean heat gone? –Out to space... or into the abyss?

2. 2005 Upper Ocean Heat Content Combined data set –Follow Willis et al. (2004) –In situ thermal data & –Satellite altimetric data 2005 relative to 1993-2002 -> –Warm subpolar N. Atlantic –Likely NAO –Warm S. Ocean band –Likely SAM 2005-2004 (Short Time-Scale) -> –Large-amplitude small-scale variations –Ocean advection –Equatorial Pacific cooling –Fading El Niño

3. Long Time-Scale (13-Year) Linear Trends Longer time-period -> Smaller amplitude & larger scale Big N. Atlantic Change –NAO 1996 shift in winds Big. N Pacific Change –PDO Large-scale wind shifts Big. S. Ocean Changes –SAM Large-scale wind shifts Overall warming trend? – ~ 5% of area at 95% CI –Hmm... –Look at global integral...

4. Annual Global Upper OHCA Variations Decadal increase: –Willis et al. (2004) –Levitus et al. (2005) What about the recent decrease? An observing system change? –Argo went global in 2004 –Remove floats (& more) blue –Don’t remove seasonal cycle red –New error analysis The cooling remains

5. Annual Global Upper OHCA Variations Levitus et al. Has Different: –Mapping –Quality Control –Data Sets (slightly) –Reference Period Similar recent cooling World Ocean 0 - 700 m

6. New Refined Error Analysis Use SSHA as upper OHCA proxy Altimetry gives 13 years of SSHA For a given year (say 1955) –Use SSHA from 1993-2005 –subsample SSHA like 1955 –Map yearly subsampled SSHA –Difference subsampled & full –Time series -> error estimate Means of + and - differences Not exactly the error estimate –Global anomalies biased low –Because no data -> no anomaly –(conservative choice)

7. Interannual Error Estimate Three different regimes –Before the XBT –XBT starts in 1960’s –Number increases –Argo starts in 2000’s –Coverage improved Note 2002 vs. 2005 –Both years ~ 150,000 profiles –Distributions different Caveat! 13-years too short –Few ENSO –NAO, PDO, etc. –Most valid from 1993 on

8. Same Profile Numbers, Different Errors Measure of in situ coverage –Blue good, red bad 2002 mostly ship tracks & moorings –Little S. Ocean coverage –Will improve with time –NODC collects data –Satellite altimetry (Aviso weekly merged delayed- mode maps) 2005 mostly float tracks –Even spatial distribution –Even temporal distribution –Few gaps –Ice –EEZs –Shallow Seas

9. Earlier Downturn in 1980’s Levitus et al. (2005) OHCA –Big 1980-1983 cooling –New error estimates –Significant –(Note caveat) Early error bars large –Likely underestimates After XBT advent –Interannual significance

10. Ocean Heat Anomaly Distribution? 1993 to 2003 change (red) –Surface intensified –Approaches 0 by 750 m –Some wiggles with depth 2003 to 2005 change (blue) –Smaller in amplitude –Surface warming –Mid-depth cooling –Approaching 0 at depth? 1993 to 2005 change (black) –More surface intensified –Surface warming –Mid-depth cooling –400-m zero-crossing

11. Heat in the Deep Ocean Levitus et al. (2005) Annual 0-700 m (red) Pentadal 0-3000 m (gray) May not be different within uncertainties Upper Ocean has most variability What about the abyss?

12. S. Atlantic Antarctic Bottom Water Warms 2005 CO 2 /CLIVAR vs. 1989 WOCE A16S & C 1995 WOCE A23 AABW changes +0.04  C warming Bottom 1500 dbar 95% significant Global budgets?