Coherence between atmospheric teleconnections and Mackenzie River Basin lake levels

Abstract

Lake Athabasca (LA), Great Slave Lake (GSL) and Great Bear Lake (GBL) lie within the Mackenzie River Basin (MRB), with GBL and GSL being the ninth and tenth largest lakes in the world by volume. How these lake levels fluctuate in time is important in management of the Peace-Athabasca delta, the ecology of these lakes, and for estimating sediment flux. The understanding of how the MRB lake levels interact with atmospheric teleconnections at different time scales may permit enhanced prediction of MRB water levels. Here we compare five teleconnections (North Pacific (NP), Pacific North American (PNA), Pacific Decadal (PDO), El Niño (MEI) and Arctic Oscillations (AO)) with lake water levels using a squared coherence analysis to determine over what timescales these teleconnections play statistically significant roles within the basin. The relevance of these interactions is then examined using power spectral analysis. We find PNA plays a considerable role in the southern half of the MRB over the interdecadal timescale. In contrast, PDO, despite having large interdecadal fluctuations, plays little role in the interdecadal lake water level fluctuations. Over the 1.1–3 year timescale, several teleconnections also show coherence with lake levels but are of less importance due to small water level fluctuations over that timescale. The coherence between LA and GSL water levels is also reduced over the 1.1–3 year timescale and may be related to flow regulation by the W. A. C. Bennett dam.