Late Holocene paleoceanographic evidence of the influence of the Aleutian Low and North Pacific High on circulation in the Seymour-Belize Inlet Complex, British Columbia, Canada |
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| Authors: | Natalia Vzquez Riveiros R Timothy Patterson |
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| Institution: | aDepartment of Earth Sciences, Carleton University and Ottawa-Carleton Geoscience Centre, 1125 Colonel By Drive, Ottawa, Ontario K1S5B6, Canada |
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| Abstract: | Foraminiferal and thecamoebian faunas from the Seymour-Belize Inlet Complex (SBIC), a fjord network situated on the mainland coast of British Columbia, were studied to assess climatic cycles and trends impacting the area through the  AD 850–AD 2002 interval. Ocean circulation patterns prevalent in the SBIC are strongly linked to precipitation, which is closely linked to the relative strength and position (center of action; COA) of the seasonally developed Aleutian Low (AL) and North Pacific High (NPH) atmospheric circulation gyres.Through interpretation of cluster analysis and ordination methods, a period of weak estuarine circulation was recognized to have impacted the SBIC area between AD 850 and AD 1500. During this time waters in the SBIC were dysoxic to anoxic and the sediment–water interface was comprised of a depauperate foraminiferal fauna consisting of low diversity agglutinated forms. These reduced oxygen conditions came about as a result of diminished precipitation in the SBIC catchment as the COA of the AL progressively migrated westward over time, resulting in greatly reduced estuarine circulation and only infrequent and feeble incursions of well oxygenated open ocean water into the SBIC basin. By AD 1575, following a gradual transition period of 75 years when circulation patterns in the inlet were unstable, very strong estuarine circulation developed in the SBIC, concomitant with the onset of the Little Ice Age (LIA) in western Canada. In the SBIC this interval was characterized by higher levels of precipitation, which greatly enhanced estuarine circulation resulting in frequent incursions of cold, well oxygenated ocean currents into the bottom waters of the SBIC and the development of a diverse calcareous foraminiferal fauna. This circulation pattern began to break down in the late 19th century AD and by AD 1940 conditions similar to those that existed in the inlet prior to AD 1500 had redeveloped, a process that continues at present. |
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