Coherence between atmospheric teleconnections, Great Lakes water levels, and regional climate

We investigated the frequency domain relationships between four atmospheric teleconnections (Trans-Niño Index TNI, Pacific Decadal Oscillation PDO, Northern Annular Mode/Arctic Oscillation Index NAM/AO, and Pacific/North American PNA pattern) and water levels in the Great Lakes from 1948 to 2002 by quantifying the coherence between these time series. The levels in all Great Lakes are significantly correlated with the TNI in the frequency range (3–7)−1 cycles year−1, and with the PDO in interdecadal frequencies. The levels in Lakes Superior, Michigan, and Erie are significantly correlated with the PNA pattern in interdecadal frequencies, and the levels in all Great Lakes are significantly correlated with the NAM/AO in interannual frequencies. We investigated also the coherence, or “climate link”, between atmospheric teleconnections and the Great Lakes regional climate, namely precipitation, evaporation, air temperature, and connecting channel flows, and the coherence, or “hydrologic link” between regional climate and lake levels. The effect of the teleconnections on lake levels is mostly transmitted through the “climate links” and the “hydrologic links”, particularly through the channel inflows to Lakes Michigan, Erie, and Ontario. Connecting channel flows depend on the cumulative effect of upstream lakes and their watersheds and transmit interannual and interdecadal signals better than precipitation, evaporation, and air temperature.