Holocene glacier fluctuations at Eklutna Lake, Chugach Mountains, south-central Alaska

Eklutna Lake, an ice-distal proglacial lake in the Chugach Mountains of south-central Alaska, preserves a continuous record of Holocene glacier fluctuations. We present a 9.6 kyr (11.15 m long) multi-proxy sediment record that integrates grain size, geochemistry, and productivity indicators to reconstruct glacier variability. The age model was constrained by radiocarbon, event markers, and tephrochronology. Most tephras were sourced from Redoubt Volcano, and two new tephras are documented here. The various indicators do not always fluctuate synchronously, reflecting sensitivity to different glacier–climate processes. Nonetheless, principal component analysis (PCA) isolated the primary variance in the dataset, providing a continuous reconstruction of rock flour abundance, validated against regional moraine chronologies and North Pacific paleoclimate syntheses. Comparison of PC1 with Holocene moraine age clusters from Alaska shows that the PC1 time series largely tracks periods of glacier expansion and stabilization. Grain size data, supported by end member modeling, show uniquely coarse grains during the early Holocene, which suggests lower lake levels until ∼8.2 ka. Subsequently, PC1 values indicate: (1) rock flour abundance was lower than at present, and glaciers were likely absent or confined to cirques until 5.5 ka; (2) a stepwise glacier expansion beginning at 5.5 ka, reaching near-modern limits by ∼4 ka; and (3) a different century-scale history of glacier fluctuations during the Common Era compared to previous varve-thickness-based glacier reconstructions from the lake. This record demonstrates how ice-distal proglacial lakes can provide a robust reconstruction of Holocene glacier variability, improving our understanding of glacier–climate linkages in south-central Alaska.