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The use of shaded digital topographic models to visualizes suites of topographic features, stratigraphy, and field mapping reveals newly recognized multiple moraines associated with oscillations of the remnants of the Cordilleran Ice Sheet in the Fraser Lowland along the western Washington–British Columbia border. Morphologic features show the extent of ice represented by Sumas Drift (ca. 11,600–10,000 14C yr B.P.), following ca. 3000 yr of retreat from the glacial maximum (Fraser Glaciation) positions 80 km south of Seattle and in the Strait of Juan de Fuca. The paleogeography of the ice margin and timing of ice retreat during the Sumas Stade is reconstructed and bracketed by 70 radiocarbon dates (24 on marine shells, 46 on wood and peat), which are secured by morphologic and stratigraphic evidence. Four topographically distinct phases of the Sumas deglaciation model are suggested.Phase SI: 11,600–<11,400 14C yr B.P., outermost drift, scattered remnants of ice-contact depositsPhase SII: 11,600–11,400 14C yr B.P., glacier readvance, building prominent moraine followed by glacier retreatPhase SIII: 10,980–10,250 14C yr B.P., glacier readvance building of multiple moraines followed by glacier retreatPhase SIV: >10,250–10,000? 14C yr B.P., glacier readvance, building of inner moraine followed by glacier retreat

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Climate variability in the Pacific basin has been attributed to large-scale oceanic-atmospheric modulations (e.g. the El Niño-Southern Oscillation (ENSO)) that dominate the weather of adjacent land areas. The Pacific Decadal Oscillation (PDO) and north Pacific index are thought to be indicators of modulations and events in the northeast Pacific. In this study we find that variations in the PDO are reflected in the terminus position of glaciers on Mt Baker, in the northern Cascade Range, Washington. The initiation of retreat and advance phases of six glaciers persisted for 20-30 years, which relate to PDO regime shifts. The result of this study agrees with previous studies that link glacier mass balance changes to local precipitation anomalies and processes in the Pacific. However, the use of mass balance changes and glacier terminus variation for identification of regime shifts in climate indices is complicated by the lack of standardized measuring techniques, differing response times of individual glaciers to changes in climate, geographic and morphometric factors, and the use of assorted climate indices with different domains and time-scales in the Pacific for comparison.

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