Abstract

The climate of the coastal Atacama Desert is dominated by marine fog, which in turn forms a unique ecosystem along the coastal cordillera (∼600–1000 masl). At present, little is known about how the climatic conditions in these fog ecosystems changed in the past or will change in the future. The Fog Oasis of Alto Patache (20°S, Chile) includes widespread archaeological, paleontological, ecological, and geomorphological evidence that remains for the most part unappreciated, despite their value as evidence for local climate change. For decades, our team, based at the Atacama Desert Center at the Universidad Católica de Chile, has studied the advective marine fog bank (camanchaca) and current physical attributes such as frequency, water-content, thickness, ecological impact, etc. Nonetheless, we still lack a basic understanding of past temporal dynamics of this extensive coastal cloud and how climate change is affecting it today and how it will change over the mid- and long-term. This is important because coastal Atacama biodiversity, plant cover, and the seed bank in the oasis are directly related to fog-water input. Plant communities at Alto Patache clearly respond to wetter conditions during El Niño years, when thick fog, dew deposition, and rain have been recorded. Nonetheless, other sources of evidence may suggest long-term wetter than present conditions in the area such as the past presence of guanacos (Lama guanicoe), as inferred from intricate network of animal trails, dusting pits and communal feces piles, the abundance of dead terrestrial gastropods and widespread dead shrubs and cacti. Moreover, archaeological evidence indicates extensive ancient human occupation at Alto Patache. In this poster, we present preliminary 14C dating results that help reconstruct fog climate variability. We compare results to other climate change proxies from the Atacama coast, including a reconstruction of past fog variability based on δ15N values on buried layers of fog-dependent bromeliad Tillandsia landbecki. With such a broad scope of past indicators of environmental variability, we aim to provide a better basis for understanding oceanatmosphere dynamics involved in fog-cloud changes over time.