Mountains, climate, and carbon 26 Jan 2015 Cin-Ty Lee

Temperature of the Earth Climate Temperature of the Earth Solar insolation Albedo Absorption greenhouse gas

What controls climate on 10-100 My timescales? ΔT (oC) +2 +4 +6 -2 -4 K J Tr P C D S O 100 200 300 400 500 Veizer et al. 2000 Prepared by Rohde Solar insolation Albedo Absorption greenhouse gas e.g., CO2

Cretaceous-Paleogene -Warm -pCO2 was >4-8 x higher than today Mid- to late Cenozoic -Cooling -Low pCO2 Zachos et al. 2001

-- what role do mountains play in climate? Whole Earth carbon cycling Global Carbon Cycle CaCO3 + SiO2 = CaSiO3 + CO2 Metamorphism, volcanism Silicate weathering, carbonate deposition Dasgupta and Hirschmann, 2010

What controls pCO2 in atmosphere? dCO2/dt = input – output If response time of ocean atmosphere is 100 ky, then on My timescales, we can assume steady state Output = k pCO2n pCO2 ~ (Input/k)1/n

How do you change the pCO2 state of the Earth?

dCO2/dt = input – output Output = k pCO2n pCO2 ~ (Input/k)1/n If response time of ocean atmosphere is 100 ky, then on My timescales, we can assume steady state Volcanoes, metamorphism, carbonate weathering Input pCO2 Output = k pCO2n pCO2 ~ (Input/k)1/n output Precipitation of carbonate Inspired by Kazumi Ozaki

Increase outputs, pCO2 decreases Increase weathering rates and carbonate deposition rates? Input pCO2 output

dCO2/dt = input – output If response time of ocean atmosphere is 100 ky, then on My timescales, we can assume steady state Input pCO2 Output = k pCO2n output Inspired by Kazumi Ozaki

Increase inputs, pCO2 increases pCO2 output Inspired by Kazumi Ozaki

Are long-term climatic oscillations “driven” by endogenic forcings (INPUTS)? Or are they “driven” by the nature of the weathering response (OUTPUTS)?

CO2 Continental Arc Island arc Magma/lava/ash Oceanic crust Sediment or carbonated crust

Global Carbon Cycle CaCO3 + SiO2 = CaSiO3 + CO2 Metamorphism, volcanism Silicate weathering, carbonate deposition Note: there’s also an organic C cycle component, but for simplicity, let’s ignore that for now Ridgwell and Zeebe, 2005

What types of mountain building processes produce the most CO2? How are these events/processes related to regional or global mantle dynamics?

An input-driven world? Did Cretaceous continental arcs intersect carbonates globally and force greenhouse conditions? Pre-Cretaceous carbonate distribution SNB SNB PRB PRB A B Lee et al., 2013; Geosphere

Zachos et al. 2001

Raymo and Ruddiman, 1992

Mountains can influence climate in other ways hydrologic cycle  chemical weathering  CO2 drawdown  temperature decrease

Journal of Climate, 2014

Molnar, Boos, Battisti 2010

Molnar, Boos, Battisti 2010

Or are we a sink-driven world…. Where the rise of mountains, enhances chemical weathering rates and burial of carbonate and organic C Did mountain building “drive” Cenozoic cooling?

Correlation does not equal causation

Surface uplift = rock uplift - exhumation Surface uplift = change in average surface elevation Rock uplift = change in elevation of uneroded rock = paleo-altimetry Exhumation = amount of overburden removed = metamorphic pressure

Paleo-altimetry represents rock uplift, not average surface elevation Could enhanced alpine glaciation, after the onset of northern hemisphere glaciation 3 Ma have caused rock uplift, masquerading as tectonics? Raymo and Huybers

How do we tease apart surface and rock uplift and exhumation?

What controls average surface elevation? Rocky Mtns, USA Andes Tibet other Elevation h (km) Thickness (km)

cgH = mg(H-h) h = (/m)H Isostasy continents ride on “fluid” substrate timescales for isostatic equilibrium is > Maxwell time (10,000 yrs) h = elevation cgH = mg(H-h) rc H rm h = (/m)H

Free-air gravity anomaly Commission de la carte geologique du monde (CCGM) Continents and oceans have near-zero free-air gravity anomalies. This means continents and oceans are in isostatic equilibrium. Even high mountain ranges like Tibet, Andes, and Cordillera are not significantly out of isostatic equilibrium. Isostatic anomalies exist on Greenland and Hudson bay and on short wavelengths due to elastic flexure on plates

Isostatic equilibrium does not mean that mountains or continents are gravitationally stable Thickened crustal columns in isostatic equilibrium can still collapse or delaminate! Zhang et al. 2004

Scatter could be related to dynamic effects or mantle buoyancy h r rc rm hb Htotal Elevations of mountains primarily controlled by crustal thickness, NOT by dynamic effects or mantle buoyancy Scatter could be related to dynamic effects or mantle buoyancy Cratons - mysterious Rocky Mtns, USA Andes Tibet other 2.6 2.7 2.8 2.9 3.0 rm = 3.33 g/cm3 Elevation h (km) rc 3.1 g/cm3 cratons Thickness (km)

What controls crustal thickness tectonics E erosion rc rm foundering M magmatism foundering & Subduction erosion

And what is the effect on Carbon Cycling? rc rm foundering M

What does the U/Pb age in zircon histogram mean? Episodic crust formation? Episodic mountain building? Biases in the composition of crust being formed? Episodic plate tectonics? What is the link with continents? Condie and Aster, 2010