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The climatic significance of clastic varves in the Ångermanälven Estuary, northern Sweden, AD 1860 to 1950Department of Quaternary Geology, Lund University, Tornavägen 13, S-22363 Lund, Sweden
Department of Mathematical Statistics, Lund University, Box 118, S-221 00 Lund, Sweden
Geological Survey of Sweden, Box 670, S-751 28 Uppsala, Sweden
Department of Quaternary Geology, Lund University, Tornavägen 13, S-22363 Lund, Sweden Multiple regression analyses were applied to decipher the correlation between monthly discharge, precipitation and temperature records and annual varve-thickness data from river Ångermanälven north-central Sweden between 1860 and 1950. Over the whole 90-year period we found generally a strong correlation between spring/summer precipitation and annual varve thickness. However, there are clear indications that precipitation during the months of January and MarchMay was more important for the formation of varves in the early part of the twentieth century, while January, March, April and June seem to have been more significant during the later part of the nineteenth century. Monthly temperatures and annual varve thickness, on the other hand, did not show any significant correlations over the whole 90-year period, but, when split into 30-year periods, a dependence of varve thickness on October (186290) and March (191950) temperatures could be observed. Our results show that it is important to test each specific varve record against instrumental data sets before any conclusions can be drawn in terms of precipitation and/or temperature dependence. They also emphasize the necessity to correlate varve-thickness records against long instrumental series in order to detect any changing forcing mechanisms.
Key Words: Varves instrumental records discharge precipitation temperature multiple regression modern analogues northern Sweden
The Holocene, Vol. 8, No. 5,
521-534 (1998) |
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