Thursday, October 11, 2012

Principle sources of paleoclimatic proxies

Studies of past climates must begin with an understanding of the types of proxy data available and the methods used in their analysis. One must be aware of the difficulties associated with each method used and of the assumptions each entails. With such a background, it may then be possible to synthesize different lines of evidence into a comprehensive picture of former climatic fluctuations, and to test hypotheses about the causes of climatic change.
Major types of proxy data available is given below; (Bradley. R.S., 1991)
1.1.     Glaciological (Ice cores):
A.      geochemistry (major ions and isotopes of oxygen and hydrogen)
B.      gas content in air bubbles
C.      trace element and micro particle concentrations
D.      physical properties (e.g., ice fabric)
1.2.     Geological:
A.      Marine (ocean sediment cores)
(i) Biogenic sediments (planktonic and benthic fossils)
(a) Oxygen isotopic composition
(b) Faunal and floral abundance
(c) Morphological variations
(d) Alkenones (from diatoms)
(ii) Inorganic sediments
(a) Terrestrial (Aeolian) dust and ice-rafted debris
(b) Clay mineralogy
B.      Terrestrial
(a) Glacial deposits and features of glacial erosion
(b) Periglacial features
(c) Shorelines (Eustatic and glacio-eustatic features)
(d) Aeolian deposits (loess and sand dunes)
(e) Lacustrine sediments, and erosional features (shorelines)
(f) Pedological features (relict soils)
(g) Speleothems (age and stable isotope composition)
1.3.     Biological:
A.      Tree rings (width, density, stable isotope composition)
B.      Pollen (type, relative abundance, and/or absolute concentration)
C.      Plant macrofossils (age and distribution)
D.      Insects (assemblage characteristics)
E.       Corals (geochemistry)
F.       Diatoms, ostracods, and other biota in lake sediments (assemblages, abundance, and/or geochemistry)
G.     Modern population distribution (refugia and relict populations of plants and animals)
1.4.     Historical
A.      Written records of environmental indicators (para-meteorological phenomena)
B.      Phenological records


1.  Bradley, R.S. and Eddy, J.A. (1991). Records of past global changes. In: Global Changes of the Past (R.S. Bradley, ed.). Boulder: University Corporation for Atmospheric Research, pg. 5-9.