Winter transport and sea level fluctuations in Hecate Strait, British Columbia

Abstract

Observed winter transport and adjusted sea level fluctuations in Hecate Strait were investigated using empirical orthogonal function and coherence analyses. The responses to large‐scale and local wind forcings were identified by the distinctive spatial patterns of their adjusted sea level responses. At the resolved periods of 2 to 48 days, the large‐scale and the local wind forcings were of roughly equal importance in driving transport fluctuations. Comparison of observations with a conceptual model indicates that the adjusted sea level in the northeast corner of the strait gives a good measure of response to both the local and large‐scale wind forcings. This provides a physical explanation for the observed high correlation between the adjusted sea level at Prince Rupert and the winter transport fluctuations in Hecate Strait. We also show that the transport fluctuations are associated with a particular spatial pattern of the velocity field, which represents roughly 1/4 of the energy in the observed winter velocity fluctuations measured at an array of current meters. This has implications for the use of surrogate transport series to hindcast oceanographic conditions in Hecate Strait.