Science motivation for 2015 CIDER Summer Program

The earth's climate system interacts with its interior in many ways, some of which are just being discovered and quantified. The role of silicate minerals on weathering reactions that drawdown atmospheric CO2 is one such interaction, and it has long been proposed as a modulator of the climate system. Feedbacks in this interaction that involve the balance between tectonics and erosion, and the effects on topography and atmospheric circulation, have been rich topics of inquiry over the last decades. Recent research highlights the importance of coupling of the hydrosphere and mantle flow through mass loading, and the importance of carbon cycling through subduction zones. The purpose of CIDER 2015 is to bring together geophysicists, geochemists, geodynamicists and paleoclimate scientists to explore emerging dynamic interactions between the solid earth and climate systems.

Coupling of the hydrosphere and mantle flow through mass loads
Glacier and ice sheet dynamics and the shape of the ocean basins control surface loading, leading to uplift or subsidence of the land surface and sea level changes over timescales that vary from years to 1000's of years. Longer-term changes in the shape of the ocean basins extend the range of timescales to 1000's of millions of years. Such loads may further drive or suppress mantle melting and volcanism, which may affect the flux of mantle CO2 to the atmosphere in a climate-mantle feedback. Proper understanding of the Earth's response to these changing loads is also critical for proper interpretation of paleoclimate proxies.

Cycling of carbon through subduction zones
The mass flux of C subducted today is driven in part by the Mesozoic climate-ocean system and its control on the burial and preservation of carbonate and organic carbon on the seafloor, now being subducted largely in the Pacific. Some of this subducted carbon returns to the earth's surface via arc volcanism, which is controlled by the efficiency of decarbonation and melting reactions in the solid earth. Are there feedbacks in this system that have affected the surface and mantle reservoirs of carbon over earth history?

Fundamental to the solid Earth-climate system are the dynamic interactions between the hydrosphere and carbosphere. How has CO2 in the atmosphere and ocean affected the balance of ice and water on the earth's surface? How does H2O mediate weathering reactions that consume CO2 and metamorphic reactions that release CO2? How do water-rich vs. carbon-rich materials affect tectonically-driven slip and deformation?

Understanding these dynamic interactions requires multi-disciplinary approaches that involve geophysical and geochemical observations; geodynamic and thermodynamic models; active monitoring of volcanic gases, river chemistry, sea level and surface deformation rates; and the study of ancient rocks, sediments and fossils.

Key questions that will be addressed during the CIDER 2015 Program:

  • What is sea level and how does it vary in space and time?
  • What controls the rate of movement of water from ice to the ocean, the flow of mantle in response, and the changes in dynamic topography and volcanism?
  • How has the volume of the ocean changed through time due to the climate vs. the subduction system?
  • Is the earth's interior a source or sink of carbon to earth's surface? What have been the changes through time in different carbon reservoirs (e.g., biosphere, sedimentary carbonate, buried organic matter, oceanic C speciation, volcanic CO2 fluxes, diamonds, carbonatite melts, etc.)

    Potential topics of discussion for the CIDER 2015 Program:

    Mantle Interactions with the Hydrosphere/Cryosphere

  • climate and sea level: variations in sea level over space and time inference of paleoconditions prediction of sea-level response to climate variations
  • measuring solid Earth deformation in response to loads across varying timescales long-term changes in relative sea level uplift and subsidence of the land surface changes in gravity field and earth rotation
  • elastic and viscous strength of crust and mantle loading and earthquakes perturb the same Earth; are rheological models consistent? what is the sensitivity of surface deformation to Earth structure and load position?
  • mantle flow is there such a thing as dynamic topography?
  • loading history (ice history, water redistribution, tectonics) ice history reconstruction coupling between mass distribution in ice, ocean, mantle how much does tectonics matter? spreading rates, continental configuration.
  • amount of water in the ocean what controls how much / how fast water moves ice -> ocean? climate forcing of temperature: Milankovitch, CO2 amplification ice dynamics (incl. geothermal heat flux) is the ocean disappearing into subduction zones? what are constraints on ocean volume from paleo data? What are constraints on (changes in) ocean volume from modern observations?

    Mantle Interactions with the Carbosphere (Continents, Ocean, Atmosphere)

  • flux of carbon from the atmosphere/continents to the ocean thru time weathering flux, river flux, alkalinity, flux from atmosphere biogenic preservation, inorganic and organic, on the seafloor; variation in CCD deep biosphere in the oceanic lithosphere alteration of the oceanic crust carbonate and organic carbon balance of the oceanic crust, and in different ocean basins
  • flux of carbon to the mantle at subduction zones over earth history subducted flux of carbon (organic and inorganic) at different margins how does carbon leave the subducting plate? decarbonation, dehydration, melting what is the fate of surface carbon in the mantle? diamonds, deep carbon
  • carbon rising from the mantle to the surface mantle melting with carbon, carbonated silicate melts in the upper mantle, redox fronts flux of CO2 from volcanoes, including diffuse flux magmatic CO2 degassed in the lower crust, stored, released tectonic flux of CO2 have MOR spreading rates varied? how has this affected CO2 fluxes? LIPS and other major events in earth history that may affect carbon interactions of magmas and C stored on the seafloor as methane hydrates rate of serpentinization of the oceanic lithosphere and associated C fluxes
  • -How does atmospheric CO2 vary over time? paleo records of carbon - ice cores, ocean seds, terrestrial stores, isotopic records tectonic drivers of atm and ocean circulation - orogenesis, continent configuration how were the early Earth carbon reservoirs different? why does the Earth's exosphere have a unique H/C ratio?

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