IMPACT OF CLIMATE CHANGE ON ROCK GLACIER DYNAMICS: SAN JUAN MOUNTAINS, CO, USA

Gradual increases in global temperatures can drive substantial changes in periglacial landforms. Because periglacial landscapes consist of various ice-related landforms, the landscape responds as a complex system of linked thermal regimes. Active rock glaciers because of an ice core or the ice-matrix structure are particularly sensitive to climate change. The impact of global warming on the thermal regime of rock glaciers could be substantial. From studies of rock glaciers in the San Juan Mountains, we have developed a model to predict pathways of change.

The model suggests that as global warming increases, physical weathering of valley walls will increase and lead to a greater production of talus. As talus slopes increase in volume, the upper reaches of rock glaciers will receive more mass and subsequent increases in rates of movement will occur. Permafrost overlain by rock glaciers will be slower to respond to change compared to melting that will occur on slopes with solifluction, stone stripes and stone terraces.

The role of liquid water in the mechanics of rock glaciers will change. In the short term, increased temperatures will result in greater volumes of liquid water being available from snow and ice melt. Seasonal fluxes in temperature plus the greater volume of liquid water will result in increased hydrostatic pressure. In the long term, the summer flow of water from rock glaciers to streams and lakes will be significantly reduced.