Lake energy balance response to 21st century warming in the tropical high Andes

Abstract

The response of Andean high-alpine lakes (>4000 m above sea level) to atmospheric warming is poorly understood, in part due to a lack of long-term limnological and meteorological observations. Here, we use in situ observations, reanalysis data, satellite-derived data, and climate modeling output data paired with a one-dimensional lake energy balance model to investigate the response of lake thermal properties to observed and projected 21st century warming in the tropical high Andes of Peru. The lake model configuration is based on Lake Sibinacocha (13.86°S, 71.02°W, 4860 m a.s.l.), the largest high-alpine lake in the Andes and one of the few such lakes with temperature observations sufficient for model calibration. Relationships between recent air and lake temperature changes were investigated using the model forced with 21st-century ERA5-Land climate reanalysis data, CERES satellite-based observations, and future relationships were investigated using two CMIP6 future climate scenarios with CESM2 (SSP2–4.5 and SSP5–8.5). Results show that Sibinacocha whole-lake average temperature stayed relatively consistent between 2000 and 2023 due to high interannual variability. Lake Sibinacocha temperatures also display interannual variability that aligns with air temperature variations, suggesting that broad climatic teleconnections that affect Andean air temperatures also influence lake temperature and stratification. Under the SSP2–4.5 and SSP5–8.5 scenarios, the model indicates an acceleration of Lake Sibinacocha's whole-lake warming rate. By 2091–2100, Lake Sibinacocha is projected to increase 2.5 °C to 5.9 °C. Lake Sibinacocha is projected to warm unevenly, with greater warming in the top 20 m and austral spring, contributing to increased weak stratification in spring. Lake Sibinacocha is anticipated to respond more slowly to warming simply due to its large size. Therefore, our results should be considered a conservative end-member for other lakes in the tropical high Andes, which, due to their shallower sizes, will likely respond more quickly to atmospheric warming.