Amazonian Climate Modeling Melinda Kahre NASA Ames Research Center CURRENT MARS + MODIFIED ORBIT PARAMETERS = AMAZONIAN MARS CO2: Measured Surface Pressure Obliquity 11 50 10 40 CO CYCLE? 9 2 30 8 20 Pressure (mb) 7 Obliquity (Degrees) 10 WATER CYCLE? 6 0 60 120 180 240 300 360 0 Ls -10 -8 -6 -4 -2 0 Time (Myr) WATER: TES Column Water Vapor (pr-um) 90 Eccentricity 0.14 DUST CYCLE? 60 0.12 30 0.10 0 0.08 Latitude -30 0.06 Eccentricity NOTE: -60 0.04 -90 0.02 • Modeling the Amazonian climate is 0 90 180 270 360 L s 0.00 disJnctly different than modeling DUST: -10 -8 -6 -4 -2 0 TES IR Dust Optical Depth: MY 26 Time (Myr) 90 Noachian/Early Hesperian climate. 60 Longitude of Perihelion • 30 Early Mars GCMs generally include 300 0 physics of massive atmospheres, 200 Latitude -30 warm water cycle physics, and 100 -60 Perihelion (Degree) 0 simplified cloud microphysics. -6.0 -5.9 -5.8 -5.7 -5.6 -5.5 -90 Time (Myr) 0 90 180 270 360 L s Laskar et al. (2004) CURRENT MARS: CO2 CYCLE Measured Surface Pressure 11 VL 1 10 VL 2 MSL 9 8 Pressure (mb) 7 6 0 60 120 180 240 300 360 Ls CO2 Condensaon & Sublimaon: CO2 Cycle Tuning: 1. Surface: • Governed by energy balance 1. Change parameters to reproduce VL 1 and 2. Atmosphere: VL 2 observed surface pressures: • Usually a simple scheme—no clouds! • CO2 ice albedo, emissivity • CO2 condenses when T<Tsat • Sub-surface H2O ice depth • Condensed mass either delivered to surface or can sublimate below 2. GCMs can readily reproduce the CO2 cycle Forget et al. (1999); Haberle et al. (2008); Guo et al. (2009) • More recently: CO2 cloud schemes CURRENT MARS: WATER CYCLE TES Column Water Vapor (pr-um) 90 60 30 0 Latitude -30 -60 -90 0 90 180 270 360 Surface Water Ice Reservoirs: Ls Importance of Water Ice Clouds: 1. “Permanent” Source: North Cap • Defined by observed T.I. or Tg 1. Radiave Influences • Simulaons show cap is not in equilibrium • Tropical clouds warm alom à Highest latudes gain annually • Feedbacks with circulaon à Lower latudes lose annually à Hadley cell intensifies 2. Seasonal/Diurnal Surface Thermal Inertia 180 800 2. Microphysical Processes • Seasonal CO2 cap -150 150 -120 120 • Clouds limit verJcal extent of H2O • Nighme frosts 600 • N-S transport influenced: Clancy effect -90 90 90 400 3. Regolith TI (MKS units) • 80 Dust needed for nucleaon! -60 60 • Omen not included 70 200 -30 30 3. GCMs now simulate H2O cycle with R.A. Clouds 0 60 Navarro et al., 2014; Haberle et al. (2017); Lee et al. (2016) 0 CURRENT MARS: DUST CYCLE (Part I) TES and THEMIS Global Average Opacity 1.2 THEMIS MY 28 1.0 0.8 0.6 9 micron Opacity 0.4 OBSERVATIONS 0.2 Dust Liming Parameterizaons: 0.0 1. Wind Stress (Saltaon) 0 100 200 300 Ls • Liming occurs when a threshold wind stress is exceeded Global Mean Dust Opacity 1.2 • Provides localized sources and storms 1.0 2. Dust Devils • Liming depends on sensible heat flux, PBL depth 0.8 • Provides background, low-level source GCM 0.6 GCMs predict low levels of dust during aphelion and Opacity increased dusJness during perihelion 0.4 0.2 0.0 0 100 200 300 Ls CURRENT MARS: DUST CYCLE (Part I) TES and THEMIS Global Average Opacity 1.2 TES MY 24 TES MY 25 TES MY 26 1.0 TES MY 27 THEMIS MY 25 THEMIS MY 26 THEMIS MY 27 0.8 THEMIS MY 28 THEMIS MY 29 THEMIS MY 30 0.6 9 micron Opacity 0.4 OBSERVATIONS 0.2 Dust Liming Parameterizaons: 0.0 1. Wind Stress (Saltaon) 0 100 200 300 Ls • Liming occurs when a threshold wind stress is exceeded Global Mean Dust Opacity 1.2 • Provides localized sources and storms 1.0 2. Dust Devils • Liming depends on sensible heat flux, PBL depth 0.8 • Provides background, low-level source GCM 0.6 GCMs predict low levels of dust during aphelion and Opacity increased dusJness during perihelion 0.4 0.2 0.0 0 100 200 300 Ls CURRENT MARS: DUST CYCLE (Part I) TES and THEMIS Global Average Opacity 1.2 TES MY 24 TES MY 25 TES MY 26 1.0 TES MY 27 THEMIS MY 25 THEMIS MY 26 THEMIS MY 27 0.8 THEMIS MY 28 THEMIS MY 29 THEMIS MY 30 0.6 9 micron Opacity 0.4 OBSERVATIONS 0.2 Dust Liming Parameterizaons: 0.0 1. Wind Stress (Saltaon) 0 100 200 300 Ls • Liming occurs when a threshold wind stress is exceeded Global Mean Dust Opacity 1.2 • Provides localized sources and storms 1.0 2. Dust Devils • Liming depends on sensible heat flux, PBL depth 0.8 • Provides background, low-level source GCM 0.6 GCMs predict low levels of dust during aphelion and Opacity increased dusJness during perihelion 0.4 Interannual variability is illusive 0.2 • Finite surface reservoirs? 0.0 Kahre et al. (2005); Newman et al. (2015); Mulholland et al (2013) 0 100 200 300 • Coupling to the water cycle through clouds? Ls Kahre et al. (2011); Jha and Kahre (2017) CURRENT MARS: DUST CYCLE (Part II) TES IR Dust Optical Depth: MY 26 90 60 30 0 Latitude -30 -60 Prescribed (or Semi-Prescribed) Dust -90 0 90 180 270 360 1. Use observed dust maps to constrain model L s Smith (2008) • VerJcal distribuJon either prescribed or self- consistently determined Montabone et al. (2015) Is τ < τ ? GCM OBS 2. The best way to control the dust cycle for current Mars simulaons Yes No • Most realisJc temperatures/circulaons Madeleine et al. (2011) 3. Not as useful for past climate simulaons Add τ = 0.1 / Sol to INSTEAD: Do Nothing Bouom Layer i. Use simplified prescripJons ii. InteracJvely predicted liming CURRENT MARS + MODIFIED ORBIT PARAMETERS = AMAZONIAN MARS CO2: Measured Surface Pressure Obliquity 11 50 10 40 9 30 CO2 CYCLE? 8 20 Pressure (mb) 7 Obliquity (Degrees) 10 6 0 60 120 180 240 300 360 0 Ls -10 -8 -6 -4 -2 0 Time (Myr) WATER: TES Column Water Vapor (pr-um) 90 Eccentricity 0.14 60 0.12 30 0.10 0 0.08 Latitude WATER CYCLE? -30 0.06 Eccentricity -60 0.04 -90 0.02 0 90 180 270 360 Ls 0.00 DUST: -10 -8 -6 -4 -2 0 TES IR Dust Optical Depth: MY 26 Time (Myr) 90 60 Longitude of Perihelion 30 300 0 200 Latitude -30 100 DUST CYCLE? -60 Perihelion (Degree) 0 -6.0 -5.9 -5.8 -5.7 -5.6 -5.5 -90 Time (Myr) 0 90 180 270 360 L s Laskar et al. (2004) MODIFYING ORBIT PARAMETERS: STRATEGY GCMs do not run fast enough to explicitly simulate changing orbit parameters. Obliquity 50 Instead: 40 30 • Choose combinaons of: 20 • Obliquity (Degrees) obliquity, eccentricity, longitude of perihelion 10 0 • Goal: map out trends and branch points in behaviors -10 -8 -6 -4 -2 0 Time (Myr) Eccentricity 0.14 Consideraons: 0.12 0.10 0.08 • Surface reservoirs and total inventories 0.06 Eccentricity 1. CO : assume enJre inventory starts in the atmosphere 0.04 2 0.02 à what about buried CO in south? 0.00 2 -10 -8 -6 -4 -2 0 2. Dust: infinite availability (?) Time (Myr) 3. Water: surface source regions depend on study goals Longitude of Perihelion 300 200 100 Perihelion (Degree) 0 -6.0 -5.9 -5.8 -5.7 -5.6 -5.5 Time (Myr) Laskar et al. (2004) AMAZONIAN MARS: CO2 CYCLE Ward (1974) Obliquity variaons have important consequences for the CO2 cycle As obliquity increases: 1. Annual mean insolaon at the poles increase • For obliquiJes > 54°: • Poles receive more insolaon than equator 2. Seasonal variaons are more extreme • Seasonal CO2 ice caps more massive & latudinal extensive • Global average surface pressure decreases Mischna et al. (2003); Haberle et al. (2003); Newman et al. (2005) When obliquity is low (< ~20°): • Permanent CO2 caps form and atmosphere collapses • Equilibrated atmospheric mass could be quite low (~30 Pa) Newman et al. (2005) Newman et al. (2005) AMAZONIAN MARS: WATER CYCLE Obliquity variaons largely control where water ice is stable on the surface Low obliquity (<30°): • Water ice is stable at the pole à N or S likely depends on Ls of perihelion • Atmosphere is relavely dry (low polar insolaon) Mischna and Richardson (2003); Forget et al. (2006); Levrard et al. (2007) Moderate obliquity (30°-40°): • Water becomes stable in the mid-latudes • Atmosphere is considerably weuer (higher polar insolaon) Madeleine et al. (2009/2012) High obliquity (>40°): Madeleine et al. (2014) • Water ice destabilized at the poles • Water ice becomes stable at low latudes Mischna and Richardson (2003); Forget et al. (2006); Levrard et al. (2007) Radiave effects of water ice clouds have significant effects! • Warm surface; enhance circulaon, cloudiness and snowfall Madeleine et al. (2014); Haberle et al. (2012); Kahre et al (2015) Forget et al. (2006) AMAZONIAN MARS: DUST CYCLE Increasing obliquity significantly enhances predicted dust liming & dust loading Increasing obliquity: • Enhances equator-to-pole temperature gradient • Drives an enhanced Hadley cell • Stronger return flow increases surface stresses • Increases dust liming Haberle et al. (2003) • PosiJve radiave-dynamic feedbacks à increases Hadley cell strength more à even more dust liming Newman et al. (2005) Newman et al. (2005) Notes and caveats: • Infinite surface dust reservoirs? • Dust-only simulaons: what would coupling to water cycle (cloud formaon) do? • Physics of liming (availability of sand, resoluJon effects)? AMAZONIAN MARS: MODELING POLAR LAYER DEPOSITS There have been a relavely limited number of GCM studies that directly relate to the PLDs 1.