Paleoclimate

VOICE 

I do not often disagree with Charles Saxon, but the bottom of the ocean may reveal a key piece of the ice age puzzle. Part of the Volcano, Ocean, Ice and Carbon Experiment (VOICE), we are exploring links between sea-level change, mid-ocean ridge volcanism and CO2  changes through the ice ages. Sea-level change during the glacial cycles causes pressure changes in the upper mantle that can lead to changes in the rates of mid-ocean ridge volcanism and in associated CO2 emissions [Crowley et al. 2015].

One way in which I am testing this hypothesis is by analyzing bathymetric variations associated with so-called abyssal hills. If, as hypothesized, these abyssal hills record the magmatic response to sea-level change they will exhibit similar Milankovitch variability [Huybers et al., submitted].

Bathymetry on the Chilean Rise containing Milankovitch variability [Huybers et al. 2015]
Bathymetry (black lines) and magnetics (red lines) from cruise PANR04MV
References:
  • Crowley, Katz, Huybers, Langmuir, and Park (2015): Glacial cycles drive variations in the production of oceanic crust, Science.
  • Peter Huybers, Charles Langmuir, Richard Katz, David Ferguson, Cristian Proistosescu, Suzanne Carbotte (2015): Comment on “Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply”. Submitted to Science.
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Orbital forcing identification under time-uncertainty

Orbital signals have been postulated for a very broad range of palaeoclimate proxy. Robust identification of orbital imprints in proxy records can both inform on dynamics and provide a basis for dating past climate and geological records. Astronomical tuning of records is performed in order to obtain a high resolution age-model when other dating methods are not available. However, testing for orbital forcing in astronomically tuned records can run into an evident problem of circularity. 

We developed a methodology that allows for a hypothesis test of orbital forcing to be performed on tuned records. The bias introduced through spurious tuning of background noise is accounted for via a Monte-Carlo method, and confidence level are adjusted accordingly [Proistosescu et al. 2012].

Oligo-Miocene δ18O records from ODP 1090. The record has been tuned to an orbital curve containing Eccentricity, Tilt and Precession (ETP).
Red line denotes appropriately adjusted 95% confidence level.
References:
  • Proistosescu, Huybers, Maloof (2012): To tune or not to tune: Detecting orbital variability in Oligo-Miocene climate records, Earth and Planetary Science Letters (pdf)