Energyexchangesbetweenthedynamic
componentsoftheclimatesystem:
atmosphereandocean
Michael Mayer
Leo Haimberger
Exeter2015
Introduction
•  Main questions: How well can we trace variability of energy flows
• 
between and within the climate components? How about trends?
Part one - global mean energy budget:
{Rad } ≈ {F } = {OHCT}
TOA
S
"+IHCT$
#
%
•  Part two - regional energy budget:
•  Atmospheric perspective:
FS = Rad TOA − ∇ • FA − AET
•  Oceanic perspective:
FS = ∇ • FO + OHCT [+ ∇ • FI + IHCT]
Exeter2015
Global mean constraints: {RadTOA} vs {OHCT}
•  satisfied by climate models but for the right reason?
•  ultimate test for climate datasets
Models(≈150yrs)
GISS-E2-R
CCSM4
Exeter2015
Global mean constraints: {RadTOA} vs {OHCT}
•  satisfied by climate models but for the right reason?
•  ultimate test for climate datasets
Models(≈150yrs)
GISS-E2-R
Reanalyses1985-2013
ORAS4/Allanetal
ReanalysesARGOperiod
ORAS4/CERES
CCSM4
HadleyEN4/Allanetal
HadleyEN4/CERES
Exeter2015
Look into OHCT layers
•  Ocean reanalyses robustly show opposite behaviour compared to
models in 100-300m layers during ARGO period – maybe realistic?
Models(≈150yrs)
GISS-E2-R
CCSM4
Reanalyses1985-2013
ORAS4
HadleyCentreEN4
ReanalysesARGOperiod
ORAS4
HadleyCentreEN4
Exeter2015
Regional energy budgets:
Tropical Pacific I
•  Lateral transports come into play
•  ENSO is the dominant mode of tropical Pacific budget variability
•  Main balance exists between OHCT, atmospheric transports and
• 
RadTOA
Small contributions from ocean heat transports
TropicalPacific(30N-30S)budgetseries[PW]
1PW≈5Wm-2
Exeter2015
Tropical Pacific II:
budget closure
• 
• 
• 
• 
Imbalance = sum of atmospheric terms minus sum of oceanic terms
Theoretically full depth OHC should yield perfect closure
In fact, budget closure is better for OHCT300
Imbalances decrease over time
! excessive oceanic variability decreases, but also correlation of
atmospheric and oceanic budget increases
Imbalanceseries[PW]
1PW≈5Wm-2
Exeter2015
Tropical Pacific II:
budget closure
• 
• 
• 
• 
Imbalance = sum of atmospheric terms minus sum of oceanic terms
Theoretically full depth OHC should yield perfect closure
In fact, budget closure is better for OHCT300
Imbalances decrease over time
! extreme oceanic variability decreases, but also correlation of
atmospheric and oceanic budget increases
Imbalanceseries(runningstandarddeviaWons)[PW]
1PW≈5Wm-2
Exeter2015
Tropical Atlantic budget
evolution I
•  ENSO also dominates tropical Atlantic budget variability – but with
• 
opposite sign
Again main balance between OHCT and atmospheric energy
transports
TropicalAtlanWcbudgetseries[PW]
1PW≈12.5Wm-2
Exeter2015
Tropical Atlantic budget
evolution II
•  Moderate decrease of imbalances over time
•  Generally weaker correlation between atmospheric and oceanic
budget than over Pacific – because of less ocean obs?
Imbalanceseries(runningstandarddeviaWons)[PW]
1PW≈12.5Wm-2
Exeter2015
Focus on ENSO: regression of budget fields vs. Nino 3.4
•  Balance between area-averaged atmospheric transports and ocean heat
content – but no local balance!
Exeter 2015
Regressed budget for all tropical basins
Pacific (30N-30S)
contribution
from
atmospheric
transports,
RadTOA and OHCT in all
basins
Good agreement between
different OHC estimates
! because imbalances are
Indian Ocean (30N-30S)
uncorrelated with ENSO!
Highest uncertainties over
Indian Ocean
Uncertainties accumulate in
zonal mean regression
•  Main
• 
• 
• 
Atlantic (30N-30S)
All tropics (30N-30S)
Exeter 2015
ENSO in CMIP5 models
•  Upper 300m OHCT vs N3.4 looks OK for 50% of models
•  Upper 700m OHCT vs N3.4 strongly underestimated by most models
•  CMIP5 models appear to redistribute tropical Pacific OHC during
ENSO rather than dis-/recharging it
! How meaningful are regional distributions of modelled OHC
variations? Trends?
•  Ocean energy divergences not stored in CMIP5 archive
TropicalPacificOHCT300
TropicalPacificOHCT700
Exeter2015
Arctic ocean (70N-90N) trends 2000-2014
•  Different estimates for
• 
end-of-melt-season
OHC
trends
agree
qualitatively
Lack of spring trends in
HEN4
demonstrates
importance of dynamical
ocean reanalysis to
carry
information
forward in time
SeasonalOHC300trends(70-90N)
YearlycycleofobservaWonsinHEN4
Exeter2015
Conclusions
•  Current (ocean) observing system is unable to satisfy global energy
• 
• 
• 
budget constraints
! one reason: large compensating regional anomalies
! currently not possible to observe EEI variations from OHC(T)
Improvement of observing system over recent decades has
demonstrably reduced uncertainties in regional coupled energy
budgets ! ENSO-related anomalies are robustly traceable with
budget statistics
Climate models conserve energy by design but interannual energy
redistributions are likely flawed
Data aspect: Committee on CMIP6 Ocean Model Output
recommends to store fields of ocean energy divergence ! ocean
reanalysis groups should do this too to enable model evaluation!
Exeter2015