Contemporary estimates for total seep refugial capacity and contributing metrics, including likelihood of seep occurrence, seep air and water temperature variability, and probability of seep permanence

We modeled the distribution and thermal and hydrologic stability of cliff-face seeps across moist portions of the Pacific Northwest, USA. We conducted surveys for cliff-face seeps across ~1,600km of roads, trails, and watercourses in Washington and Idaho and monitored water availability and air and water temperatures at a subset of these seeps. We detected 457 total seeps through an iterative process involving surveying, modeling, ground-truthing, and then remodeling the spatial distribution of seeps using boosted regression trees. Additionally, we used linear and generalized linear models to assess environmental correlates of seep thermal and hydrologic stability. Seeps were generally most concentrated in steep and relatively low-lying areas (e.g., towards the bottom of deep canyons or the base of tall cliffs), and were also positively associated with basalt, glacial drift, or graywacke bedrock, high average slope within 300m, and low average vapor pressure deficit. North-facing slopes were the best predictor of stable air and water temperatures and perennial seep discharge, and relatively low-lying areas also predicted stable seep water temperatures.