Late Holocene droughts and cave ice harvesting by Ancestral Puebloans

Abstract

Water availability for Native Americans in the southwestern United States during periods of prolonged droughts is poorly understood as regional hydroclimate records are scant or contradicting. Here, we show that radiocarbon-dated charcoal recovered from an ice deposit accumulated in Cave 29, western New Mexico, provide unambiguous evidence for five drought events that impacted the Ancestral Puebloan society between ~ AD 150 and 950. The presence of abundant charred material in this cave indicates that they periodically obtained drinking water by using fire to melt cave ice, and sheds light on one of many human–environment interactions in the Southwest in a context when climate change forced growing Ancestral Puebloan populations to exploit water resources in unexpected locations. The melting of cave ice under current climate conditions is both uncovering and threatening a fragile source of paleoenvironmental and archaeological evidence of human adaptations to a seemingly marginal environment.

Climatic backdrop for Pueblo cultural development in the southwestern United States

“…Several decades later, five aragonite layers (droughts) occur within a span of ~ 30 to 40 years (~ ≤ 8 years per drought defined by aragonite layers) starting at 1180 ± 125 yr B2K. The four dates in magenta between 1050 and 1300 yr B2K represent the timing of droughts from charcoal layers in ice deposits in Cave 29 of El Malpais National Monument 42 . The date at 913 yr B2K on charcoal attached to a corrugated pottery sherd also likely represents a drought 42 .…”

“…The four dates in magenta between 1050 and 1300 yr B2K represent the timing of droughts from charcoal layers in ice deposits in Cave 29 of El Malpais National Monument 42 . The date at 913 yr B2K on charcoal attached to a corrugated pottery sherd also likely represents a drought 42 . All of these are comparable with droughts represented by aragonite layers in stalagmite HC-1.…”