Tidewater calving glaciers have been hypothesized to act independently of climate during most of their advance/retreat cycle, causing asynchrony between calving glaciers and nearby alpine glaciers. However, eighty to ninety percent of the tidewater calving glaciers in Alaska have retreated in the last 200 years, implying a related cause. It seems likely that this cause was the global rise in ELA between ca. 1800 and 1950 A.D.

To test this hypothesis, a simple model was constructed using modern accumulation area ratios and cumulative area-altitude curves from glaciers in different stages of the tidewater calving glacier advance/retreat cycle. For advance to occur, a tidewater glacier must decrease the water depth at the terminus by building a terminal moraine shoal, thereby decreasing calving flux. During advance, the accumulation area ratio decreases, indirectly reducing the ice flux at the terminus. Therefore, the terminus advances down-fiord in a state of quasi-equilibrium, where ice flux at the terminus and calving flux are nearly equal. This relationship is expressed as a positive correlation between water depth at the terminus and the accumulation area ratio. Durung this stage of the cycle, a rise in the equilibrium-line altitude can result in reduced ice flux at the terminus, causing the terminus to recede. Once the glacier retreats from the shoal into deeper water, a progressive increase in the calving flux can lead to irreversible retreat of the terminus. During retreat the glacier is decoupled from climate, and is insensitive to a change in the equilibrium line altitude. These data imply that tidewater calving glaciers are sensitive to climate during approximately ninety percent of the tidewater-calving glacier cycle. If interpreted correctly, tidewater-calving glacier moraines can be used to reconstruct paleoclimatic conditions and cumulative area-altitude curves can be used to predict future tidewater glacier fluctuations.