Overview

Overview

1. Orbital Forcing of Climate

   • Milankovik Cycles
     • Eccentricity
       • Amount by which the orbit deviates from a perfect circle
     • Obliquity
       • Tilt of the Earth, determines the intensity of the seasons
     • Equinoxes
       • Flipped every 10 500 years
   • What happens at 50-75 degree latitudes, where there is low albedo, may drive global climate change.

2. Solar Forcing of Climate

   • Solar Cycles
     • Schwabbe, 11 years
     • Hale, 22 years
     • Gleissberg, 88 years
     • Suess/ de Vries, 205 years
     • Hallstatt, 2300 years
   • There is a correlation between the absence of sunspots and a cooling climate
     • 17th century, Little Ice Age
   • Ultraviolet cycles
   • Flare Cycles

3. Sea-Level Change and Tsunamis

   • Glacio-isostacy
     • Weight of the ice depresses the crust. Melting of the ice causes the collapse of the forebulge and the rebound of the ice centre
   • Mechanisms for change
     • Change in ocean basin volume
     • Change in water temperature
       • Thermal expansion/ contraction
     • Change in water volume
   • Storegga
     • Volume of slide estimated to be 2400km3
       • Bondevick et al. 2005
     • Highest deposits found in Shetland, at Sullom Voe
       • Sand found 20m above estimated sea level at that time
         • Bondevick et al. 2005
     • Slides are linked with glacial cycles
       • Glacio-isostacy caused strong earthquakes triggering the slides
         • Frequency of every 100000 years over the past 0.5 Ma
           • Smith et al. 2004
         • Bryn et al. 2005
     • Deposits are generally consistent, a sheet of fine-medium sand with a similar morphology at most sites though with courser material at the base.
       • Smith et al. 2004
     • Sissons and Smith (1965) first identified the layer in the western Forth Vally, but attributed it to river flooding.
       • Singularity of deposit meant flooding was rejected
       • Smith et al. 2004
     • Bondevik et al. 2005
     • Most studies attribute seismic activity, glacio-isostatic uplift, sediment loading and gas hydrates as the causal mechanism
       • Smith et al. 2011 think sea level rise should be considered as a causal mechanism. As 2 clusters of slides have occured in times of sea level rise
   • 8.2k Event
     • Lasted 150 years
       • Kobashi et al. 2007
     • Global mean SL rise of 0.4 m
       • Varied regionally, perhaps on a metre scale.
       • Smith et al. 2011
     • Lake agassiz outflowed out of the Hudson strait, slowing down ocean circulation
       • Kobashi et al. 2007
     • Linked to an increase in C14 (Methane) levels
       • Rejected as a cause by the Storegga slides due to inconsistent dates
         • Dawson et al. 2011

4. Oxygen Isotope Records

5. Terrestrial Sedimentary Evidence

6. Dendrochronology

7. Cosmogenic Exposure-age Dating

8. Tephrochronology

9. Biological Evidence

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