About my thesis 2010/03/02 Pei-Yu Chueh
Motivation • An Inconvenient Truth: The temperature was determined by the concentrations of carbon dioxide. (Al Gore) • The measurement and results obtained on ice cores indicate that the CO2 increase lags the temperature at the onset of the last glaciation. • The close correlation between Vostok δO18 and CO2 and the saw-tooth patterns.
Northern Hemisphere forcing scenario • Orbital variations on surface solar insolation (eccentricity 100kyr, tilt 41kyr, precession 22kyr, insolation varies from latitudes) • When NH spring insolation peaks, we expect ice melt to change (1) ice albedo (2) Atlantic fresh water input. • Moderate insolation forcing and ice volume together play a role in triggering of deglaciations. • Orbital forcing → temp raise →warm water input → gas hydrate dissociate • northern-lead, also proposes atmospheric CO2 as the essential amplifier of the warming and cooling and hence the waxing and waning of global ice volume
Southern Hemisphere forcing scenario • Astral spring insolation and sea salt flux correlate well → change astral temperature → sea ice variations • Change ocean ventilation dynamics → particularly in the Southern Ocean. • Overturning around Antarctica tends to switch (global carbon cycle ) • Changes in insolation patterns would have triggered the warming of tropical pacific→ heat transport to both hemispheres but with a significant bias towards the south. (“conveyor belt” circulation) • External orbital insolation triggered the fast and large changes in the air temperature in the SH → cause responses in deep ocean properties & global carbon cycle → changing levels of atmospheric CO2
CO2’s role • Lagged 800~1000yrs behind temperature. (Antarctica) • CO2 plays a key role in amplifying the initial orbital forcing? • CO2 may be controlled in large part by the climate of the southern ocean. • Possible explanation: change in the vertical ocean mixing or sea-ice cover changes, or a biological mechanism, such as atmospheric dust flux and ocean productivity. • A CO2–climate lag time of 800 years is consistent with the mixing time of the deep ocean and is much longer than the time required for warming and degassing of the surface ocean.
OUR HYPOTHESIS • Our basic hypothesis is that long-term climate change is driven by insolation changes, especially orbital forcing. The climate system is like a energy capacitor. • Insolation→ chemical energy → bond energy with molecules → clathrate hydrate → change temp & pressure → hydrate dissociate →intermediate water warms up • The land-sea distribution favors the N.H for the onset of a GT.
Objective • Use statistical techniques to analyse the paleoclimate data. • Use model to prove our idea. (external forcing dominate) It’s much easier to do short-term work. (model) • Without solar forcing • With solar focing →compare with observation