A lichenometrical study of snow patch variation in the Frederikshåb district, South-West Greenland, and its implications for studies of climatic and glacial fluctuations

G.T.K Pitman

doi:10.34194/bullggu.v104.6645

Abstract

This report describes firstly the methods used to determine local growth rates of the species Rhizocarpon geographicum and the confidence that can be put in such estimates of substrate age based on lichen diameters. Secondly, mean Rhizocarpon geographicum diameters in former snow patch zones were sampled and non-random patterns of colonization were observed. Two models were constructed to explain these colonization patterns in terms of the change of the perennial snowline with height against time. Hence mean annual temperatures back to 1680 were predicted from the models for Frederikshåb. Lastly a correlation is shown between local mean annual temperature changes in the historical period, glacial fluctuations, and estimates of temperature obtained from the lichen colonization models.

Highlights

The field work which forms the basis of this paper was undertaken in the summer season of 1968 during the mapping of the superficial deposits for the Geological Survey of Greenland in the north Frederikshåb district
Developed by BESCHEL (1950, 1957, 1958) the method of lichenometry permits absolute dating of the underlying substrates from a knowledge of the local lichen growth rates
The assumptions made in lichenometry have been reassessed by ANDREWS & WEBBER (1969), following the criticisms put forward by JOCHIMSEN (1966) regarding the linearity of growth rates: provided that sufficient care is taken in the method their reexamination demonstrated that the technique was valid

Summary

Introduction

The field work which forms the basis of this paper was undertaken in the summer season of 1968 during the mapping of the superficial deposits for the Geological Survey of Greenland in the north Frederikshåb district. Tests of randomness were applied to the data (KERSHAW, 1964; LINDGREN & McELRATH, 1959) and it was found that the distributions observed were not random i.e. the lichen growth varies systematically according to its distance from the centre of the snow patch.

Results

Conclusion