| Popis: |
Two cores from the sub-arctic Swedish Angermanaalven river valley and estuary contain sedimentary laminae with variable thickness changes. One core contains a major 27–28 month period and several lesser lines of marginal statistical significance. The strong signal suggest a record of a northern latitude quasi-biennial oscillation (QBO). The record in seasonal riverine sedimentation covers a period of half a millenium. Corresponding data from the “downriver” estuarine (piston) core fail to show a QBO-like period but disclose periods of 3.6, 3.8, 7.6 and 19.1 years, some of which may be tidal, though their statistical significance is probably questionable. As a working hypothesis the watershed serves as a large area seasonal precipitation concentrator similar to the case of the Harding ice field and Skilak lake, Alaska. If so, what is witnessed is an equatorial to polar transport of moisture modulated by the equatorial QBO. An alternate model would be based more directly upon temperature, i.e. glacial melt. Combination of these cannot be ruled out. No evidence for solar forcing at an 11-yr period is found in either core, contrary to Skilak Lake, Alaska varve data. |
