Spatial distribution and interannual variability of coastal fog and low clouds cover in the hyperarid Atacama Desert and implications for past and present Tillandsia landbeckii ecosystems

Abstract

The hyperarid Atacama Desert coast receives scarce moisture inputs mainly from the Pacific Ocean in the form of marine advective fog. The collected moisture supports highly specialized ecosystems, where the bromeliad Tillandsia landbeckii is the dominant species. The fog and low clouds (FLCs) on which these ecosystems depend are affected in their interannual variability and spatial distribution by global phenomena, such as ENSO. Yet, there is a lack of understanding of how ENSO influences recent FLCs spatial changes and their interconnections and how these variations can affect existing Tillandsia stands. In this study, we analyze FLCs occurrence, its trends and the influence of ENSO on the interannual variations of FLCs presence by processing GOES satellite images (1995–2017). Our results show that ENSO exerts a significant influence over FLCs interannual variability in the Atacama at ~ 20°S. Linear regression analyses reveal a relation between ENSO3.4 anomalies and FLCs with opposite seasonal effects depending on the ENSO phase. During summer (winter), the ENSO warm phase is associated with an increase (decrease) of the FLCs occurrence, whereas the opposite occurs during ENSO cool phases. In addition, the ONI Index explains up to ~ 50 and ~ 60% variance of the interannual FLCs presence in the T. landbeckii site during summer and winter, respectively. Finally, weak negative (positive) trends of FLCs presence are observed above (below) 1000 m a. s. l. These results have direct implications for understanding the present and past distribution of Tillandsia ecosystems under the extreme conditions characterizing our study area.

Life Cycle of Stratocumulus Clouds over one Year at the Coast of the Atacama Desert

“…While Schulz et al (2012) found a weak decrease in cloud cover, Muñoz et al (2016) could show that with higher temporal resolution and restriction to low clouds only, a long term increase in spring and decrease in fall as well as a cloud base decrease of 100 m per decade can be found. A similar pattern in cloud cover can be found in satellite data with a weak increase in cloud cover in winter and spring especially over the ocean, and a decrease above land with altitudes above 1000 m asl (del Rio et al, 2021a). Besides these weaker long term trends, cloud cover shows a strong inter-annual variability which is connected to the El Niño Southern Oscillation (ENSO) global circulation pattern with opposite effects in different seasons.…”

“…During an El Niño phase with warm equatorial waters cloud cover is, in comparison with other years, increased in summer and decreased in winter and vice versa in La Niña years (del Rio et al, 2021a).…”

Leaf wax composition and distribution of Tillandsia landbeckii reflects moisture gradient across the hyperarid Atacama Desert

“…30% of annual rainfall at Arica (Houston 2006;Schulz et al 2011). Fog occurs frequently along the coastal Cordillera when the massive marine Stratocumulus (Sc) cloud deck that covers a large portion of the subtropical southeast Pacific approaches the coastal cliff (Cereceda et al 2008;Schween et al 2020;Del Río et al 2021). Advection of marine Sc air masses facilitate fog formation in the morning and evening/ night, while changes in air circulation during the afternoon produce thermal stratification that dissipates fog (Muñoz et al 2016;Lobos Roco et al 2018;Schween et al 2020).…”

“…Besides infrequent rainfalls, marine advective fog from the Pacific Ocean is the most important source of moisture along the Atacama Desert (Cereceda et al 2008;Lobos Roco et al 2018;Schween et al 2020;Del Río et al 2021). Frequent coastal fog events are generally considered to be restricted to distances of up to a few kilometers from the coast and elevations of about 100-1200 m (Caviedes 1973;Prohaska 1973;García et al 2021;Del Río et al 2021).…”

“…Besides infrequent rainfalls, marine advective fog from the Pacific Ocean is the most important source of moisture along the Atacama Desert (Cereceda et al 2008;Lobos Roco et al 2018;Schween et al 2020;Del Río et al 2021). Frequent coastal fog events are generally considered to be restricted to distances of up to a few kilometers from the coast and elevations of about 100-1200 m (Caviedes 1973;Prohaska 1973;García et al 2021;Del Río et al 2021). Beyond these elevations, hyperarid conditions limit the growth and survival of plants on the landscape and extensive areas without any vegetation exist, especially in the hyperarid core of Atacama Desert (Arroyo et al 1988;Rundel and Dillon 1998;Schulz et al 2011;Knief et al 2020;Merklinger et al 2020).…”