Theory, Mechanisms and Hierarchical Modelling of Climate Dynamics: Multiple Equilibria in the Climate System ICTP, June, 2018 Monday Morning Tuesday Morning Energy transport by A & O, Fundamentals of Atmospheric Dynamics Climates of Aquaplanets In-Sik Kang (SNU, Republic of Korea) Oceans Climate Asymmetries John Marshall (MIT, USA) Tuesday Afternoon Multiple equilibria in the climate system: Monday Afternoon understanding the role of oceans and sea ice Modeling Tutorials Brian Rose (U. Albany, USA) Stephen Thomson (Exeter, U.K.) Thursday Morning Wednesday Morning Tropical convection and large-scale circulation Structure of the tropics and midlatitudes Monsoons, tipping points Geoffrey Vallis (U. Exeter, U.K.) Simona Bordoni (CALTECH, USA) Wednesday Afternoon Thursday Afternoon Multiple equilibria to and paleoclimate Tropical ocean-atmospheric feedbacks David Ferreira (U. Reading, UK) Shang-Ping Xie (SCRIPPS, USA) Friday Afternoon Friday Morning Vegetation-Carbon-Cycle-Climate Feedbacks Regimes and Predictability of atmos flow Ning Zeng (U. Maryland, USA) Franco Molteni (ECMWF, U.K.)
Coupled Climate Dynamics: Energy transport by the Atmosphere and Ocean John Marshall, MIT 1. Energy transport by A & O Observations Importance of hierarchical modeling 2. Climate of an Aquaplanet 3. Oceans and Climate asymmetries
1. Energy transport by A & O Observations Importance of hierarchical modeling Figs from Marshall and Plumb, 2008
Earth’s Energy Balance Net top of the atmosphere Two important consequences 1. Warmer, and moister, in the tropics than at higher latitudes 2. Atmosphere, and ocean, must transport, energy from low to high latitudes
Warm, and moist in the tropics
Warm, and moist in the tropics
Energy budget of the atmosphere and ocean Total Northward Energy Transport Atmos + Ocean PW � 10 15 W Note:
Air-sea heat flux Out of ocean In to ocean
Ocean heat transport, basin by basin Atlantic Indian
Northward Energy Transport by Atmosphere and Ocean Trenberth and Caron, 2001 Notes: - Atmosphere dominates over ocean in middle to high latitudes - Ocean transports substantial amounts of heat out of the tropics - Error bars are considerable
Key climate questions • What determines the total meridional energy transport and its partition between the atmosphere and ocean? • What sets the pole-equator temperature gradient? • What determines the extent of polar ice caps? • To what extent is the ocean ‘slaved’ to the atmosphere? • Can more than one climate state exist for the same external forcing? Trenberth and Caron, 2001 See afternoon sessions by Brian Rose and by David Ferreira
Framework for thinking about Energy Partition between A and O Plot mass transport in energy space Meridional energy transport is: H � � � � B Mass Energy transport contrast Atmos J kg � 1 kg s � 1 Ocean Note: If we define a Sverdup (Sv) as 10 9 kg s � 1 then can readily compare the mass transports in each fluid.
Example Ocean circulation Warm, salty lenses driven by the wind, floating on a well-mixed abyss. Abyssal ocean, ventilated by convection from poles Meridional energy transport 10 3 � 20 � 10 6 � 4000 � 15 � H O � � � vol � c p � � � o C o kg m � 3 m 3 s � 1 � � � 1.2 � 10 15 W � B
Asymmetry of stratification of A and O in deep tropics � e moist � e Atmos convection � Ratio of Ratio of Ratio of energy mass stratifications transports transports � Ocean � A � O � 1 Note – in atmosphere need � B A H A H O � � B O � 1 to consider moist static energy Held, 2001 B A � C A T � gz � Lq Czaja and Marshall, 2006
Observational estimates p � � p � � �� � v � p � v � z � g from NCEP re-analyzed � � A & � B A p B A � C A T � gz � Lq Moist static energy 120Sv � A � O Dominance of over 30Sv H O H A is a consequence of � A �� � O 1 Sv � 10 9 kg s � 1 Czaja and Marshall, JAS, 2006 How robust is this partition? Could it have been different in past, in future?
Modeling hierarchies ‘Sim - Earth’ 2-box model Modeling hierarchies Pole Eq Observed Climate
Modeling hierarchies
Modeling hierarchies
Modeling hierarchies
Modeling hierarchies
Modeling hierarchies
Modeling hierarchies Ken Fallin
Ken Fallin ‘Ken takes a sharp look, brandishes his steel quill, and traces in ink the essence of a living soul’
Climate of a Water World What would the climate of earth be like if there were no land? Coupled A, O, Ice model Aqua Ridge barrier Drake A, O, possibility of Ice, but no land Double Explore with a series of Drake numerical simulations of highly idealized water worlds
Coupled Climate Dynamics: Energy transport by the Atmosphere and Ocean John Marshall, MIT 1. Energy transport by A & O Observations Importance of hierarchical modeling 2. Climate of an Aquaplanet 3. Oceans and Climate asymmetries
Aqua-planet Project Aqua-planet Project Vorticity at ocean’s surface Thanks to: Martha Buckley J-M Campin Aaron Donohoe Daniel Enderton David Ferreira Brian Green Mukund Gupta Chris Hill David McGee Paul O’Gorman Brian Rose Sara Seager Applied to: Series of papers by John Marshall, Brian Rose, Understand present climate David Ferreira & collaborators Paleo climate Multiple equilibria of climate Riccardo Farneti & Geoff Vallis Exoplanets
Climate of an Aquaplanet What would the climate of earth be like if there were no land? How would it achieve the requisite meridional energy transports? http://oceans.mit.edu/JohnMarshall/research/climate-dynamics/page-1/
Coupled Climate Model Fully coupled: no adjustments MITgcm Poles well represented A & O on same grid ICE Winton, 2000 Intermediate ‘SPEEDY’ complexity 2000 years in 1 week of CPU time Franco Molteni, 2003 (synchronous) J-M Campin and Chris Hill built the model David Ferreira helped drive forward the science
Aqua-planet
Sea Surface Temperature & Sea Ice Sea-ice thickness (m)
Climate of aqua-planet Winds, Specific q U Currents humidity and Temp � A 500mb T q ICE U � O S Salinity A S � x 60N 30N Circumpolar Equator Circumpolar currents currents everywhere everywhere Zonal jets Aquaplanet solution discussed in in ocean Surface Winds Marshall, Ferreira et al JAS, 2007
Eulerian view Aqua planet PW � Eu H A � H O H A � � � A H O z or p � � � res Subtropical Cells Today’s climate O Residual view 200 Mass transport Sv streamfunction � A energy 45 � O Sv
Dominates in Interpretation extra-tropics � A � � � s f � � A v � h � A Atmosphere � s bolus transport � O � � � s f � � O v � h � O Ocean Balance one-another in extra-tropics � O � A � 1 In tropics � O v � h � O � O � A � In extra-tropics � A v � h � A v � h � � v � � � Now � Ks � � z where K is an eddy diffusivity. If isentropic slopes in the two fluids are comparable, then � O � O K O 1 � A � � A K A � 4 K A � 4 � 10 6 m 2 s � 1 supposing that typical of turbulent K O � 10 3 m 2 s � 1 diffusivities in A and O
Why ice at the poles in aqua? H � � � � B Mass transport streamfunction energy � A � O H O Poleward mass transport in the ocean Very small high latitude meridional all but vanishes at high latitudes energy flux Pole freezes over
Conclusions • Energy flux partition can be rationalized by 120Sv � A H A H O Dominance of over � O 30Sv � A �� � O is a consequence of 1 Sv � 10 9 kg s � 1 • Partition of heat transport on aqua-planet remarkably similar to present climate Can interpret using zonal-average theory • Ocean energy transport on aqua-planet very small at high latitudes Vanishing of residual flow at high latitudes Ice builds up over the poles As we shall see, the aqua-planet supports multiple equilibria
Recommend
More recommend
