1. Ocean Heat Uptake Gregory C. Johnson 1,2, John M. Lyman 3,1, & Sarah G. Purkey 2,1 1 NOAA/Pacific Marine Environmental Laboratory, 2 University of Washington School of Oceanography, 3 JIMAR University of Hawaii What is the global heat reservoir for climate? – The Ocean! How much heating has gone where on Earth? What is the upper ocean heating since 1993? How are the data taken? How much data are available? What about the deep ocean? How important AABW vs. NADW ventilation? What is the AABW warming over 1990s–2000s? Feedback, forcing, transient? (  Q =  T +  F ) What is a petawatt or a zetajoule? What are the consequences for climate projections? What are the different time-scales?

2. Net heat input to Earth’s climate system ~0.24 W/m 2 Incoming heat Outgoing heat Top of atmosphere 342 W/m 2 Sun 1961-2003: Oceans Take up 89% of Heat Absorbed by Earth (from IPPC AR4, Figure 5.4) Total is 159 Zeta-Joules (or 0.24 W/m 2 applied over the entire surface area of the Earth over that entire time period) Note: Ocean rate from 1993–2009 estimated at 0.74 W/m 2

3. Error Budget uses curves from numerous investigators Upper Ocean Heat Content (1993–2008) (Lyman et al. 2010 – Nature)

4. Reversing Therm. (courtesy SIO) MBT not shown Subsurface Mooring (courtesy TAO/PMEL) Conductivity, Temperature, Depth (CTD) XBT (left) & Argo Float (right) Diverse Data Sources

5. Three Different Sampling Eras 2004–Present (Argo) Near-global (90%) coverage to 2 km year-round sampling High quality data 1967–2003 (XBT) About 70% coverage to 700 m Not much winter data Lacks S. Ocean data (shipping lanes) XBT Instrument Biases Good CTD & reversing therm data Pre-1967 (Reversing therm & MBT) About 30% coverage to 300 m MBT instrument biases Reversing therm. data good quality

7. AABW Dominates the Abyss (Johnson 2008) NADW prominent in W. Atlantic Mid-depth ACC AABW dominates elsewhere AABW NADW Atlantic Pacific

8. Western S Atlantic Warms 2005 – 1989 (Johnson and Doney, 2006) AABW Warming: S. Ocean mid-depth Abyssal northward Mean 0.04  C warming 16-year time interval Brazil

9. Local decadal heat content changes (W m -2 ) for z > 4000 m The closer to AABW sources, the larger the heat gain. 9 of 17 warming basins significantly different from zero at 95% 1 of 7 cooling basins significantly different from zero at 95% S. Ocean for 1 > z > 4 km (magenta line & #s) also warms Abyssal & Deep Heat Content Changes (Purkey & Johnson, in press, J. Climate)

10. Global Abyssal & Deep S. Ocean Changes (Purkey & Johnson, in press, J. Climate) RegionGlobal Heat Gain (W m -2 ) Abyssal Ocean (z > 4 km)0.027 (±0.009) Southern Ocean (1 > z > 4 km)0.068 (±0.062) Total (Abyssal + Southern)0.095 (±0.062)

11. TOA flux entering the oceans in 1990s – 2000s is ~0.74 W/m 2 Global ocean heat uptake ~0.38 PetaWatts of power: ~25 times humankind’s 2008 rate of energy use ~7 Hiroshima Bombs per second ~45 1200-watt hair dryers running continuously for each of the 6.86 billion people on earth One decade of ocean heat uptake ~119 ZetaJoules of energy: Causes ~1.35 cm of thermosteric sea level rise Energy sufficient to melt land ice to raise sea level by ~1 m Energy sufficient to warm upper 50 m of world ocean by ~1.6°C Ocean has ~1000 times atmosphere’s heat capacity Energy sufficient to warm the atmosphere by ~23°C What is a PetaWatt or a ZetaJoule?

12. Climate Change Models: AABW Warming (Stouffer et al. 2007) Freshwater Hosing Experiment – continuous surface input Atlantic Overturning Streamfunction Control shows NADW cell Also strong AABW cell: S. Ocean freshening shuts it down Global S. Ocean & deep ocean warm IPCC AR4 models show similar patterns (Gupta et al., 2009) Getting all the ocean warming & causes requires observations and study of all depths including the S. Ocean

13.  Q =  T +  F Radiative Forcing (  Q) change partitioned between increased heat loss to space (  T) and uptake of heat by the ocean (  F) where  T is the global average tropospheric temperature change and is a climate feedback factor Ocean Heat Uptake and Climate Sensitivity (Raper et al. 2002) Largest climate sensitivity model takes up the most ocean heat (and the most heat deep in the ocean). What is going on in the ocean depths is important for climate. Also important for sea level rise.

14. Different CO 2 concentration scenarios CCSM3 (solid-higher sensitivity) PCM (dashed-lower sensitivity) Different sensitivities -> different surface temps Some indications that ocean heat uptake (including deep ocean) related to climate sensitivity Deep overturning difficult to model Deep temperature drift in models too Global air temperature equilibrates within decades of CO2 stabilization: Upper ocean temperature adjustment important Sea level rises for centuries after stabilization: Large heat capacity and long ventilation time- scale of the deep ocean important (ice melt too) The Oceans & Climate (Meehl et al. 2005)

15. Ocean is taking up most of the global warming heat at present primarily in the upper ocean deep ocean ~1/8 th of net ocean Deep warming widespread Largest near Antarctica Smaller distant from S. Ocean Upper ocean temperature record has Instrument biases (XBT, MBT) Sparse historical sampling Deep ocean temperature record has Very high-quality measurements since 1980’s But very sparse sampling Ocean warming (1990s-2000s: 0.74 ± 0.13 W/m 2, less when including earlier times) & its vertical distribution important for: Quantifying global energy imbalance Transient response (commitment) and climate sensitivity Sea level rise contribution Conclusions