Download 28. 24 April

24 April 2014 – Geog 3601 Lecture Summary
1. Paleoclimatology Datasets
Continued our discussion of this web site:
www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets
and the handouts Tables 1.1 and 1.2.
My expectation is that you become educated on any two datasets.
Specifically:
- Summary of the method
- Advantages and Disadvantages
- Appropriate time scales
2. Stable Isotopes
-
Used for long-term climate trends e.g. 100,000 – 400,000 years
ice -
Isotope Definition: Any element, # of protons (atomic number) is invariant, but # of
neutrons may vary, resulting in different isotopes of the same element
Example: Carbon – always 6 protons, but may have 6,7, or 8 neutrons.
Atomic Mass = total number of protons and neutrons:
C
C
C
P
6
6
6
+
+
+
N
6 = 12C
7 = 13C
8 = 14C
O
O
8
8
+
+
8 = 16O
10 = 18O
light
heavy
light
heavy
Warm World:
Ocean sediment:
Ice Core:
enrichment of 18O relative to 16O
enrichment of 16O relative to 18O
Cool World:
Ocean sediment:
Ice Core:
enrichment of 16O relative to 18O
enrichment of 18O relative to 16O
Such measurements have revealed that climate change can be rapid (decades) and
global (pole-to-pole). E.g. Figure 11-8 on handout – positive feebacks were
discussed. What are examples of mechanisms that could create such rapid and largescale climate change?
-
Large volcanic eruptions
Magnetic field changes
Large asteroid impacts
Ocean circulation changes
3. Began our discussion of Milankotich Theory
- See figure 11-9 (handout) and this website:
www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch
-
We discussed the significance of 65 deg N latitude in June
We discussed: Eccentricity; Obliquity; and Precession