Pleistocene Smoothing and Resurfacing of Appalachian Ridgelines by Periglaciation

Pleistocene cold periods created widespread periglacial conditions across mid-latitudes, but isolating their geomorphic impact from modern climate, tectonics, and rock strength is challenging. We studied Appalachian (Eastern U.S.) ridgelines across a paleoclimate gradient, controlling for bedrock and structure, to test if colder periglacial conditions led to flatter hilltops and longer hillslopes, features typical of permafrost landscapes. We find that hilltop curvature and hillslope length vary with paleotemperature, not modern climate or uplift. Despite gentler slopes, erosion rates near the Last Glacial Maximum ice margin are similar or higher than southern sites for resistant bedrock units, suggesting frost cracking and solifluction enhanced hilltop lowering and valley infilling. Hillslope morphometry patterns resemble landscapes responding to modern Arctic climate gradients, implying a long-lived geomorphic signature of permafrost-driven processes. This cold-climate legacy can remain imprinted in modern mid-latitude terrain, complicating efforts to link current climate with landscape form where erosion rates are slow.