Slow response of surface water temperature to fast atmospheric variability reveals mixing heterogeneity in a deep lake

Marina Amadori; Mariano Bresciani; Claudia Giardino; Henk A Dijkstra

doi:10.1038/s41598-024-58547-0

Slow response of surface water temperature to fast atmospheric variability reveals mixing heterogeneity in a deep lake

Sci Rep. 2024 Apr 11;14(1):8459. doi: 10.1038/s41598-024-58547-0.

Authors

Marina Amadori¹, Mariano Bresciani², Claudia Giardino², Henk A Dijkstra^{3

4}

Affiliations

¹ Institute for Electromagnetic Sensing of the Environment, National Research Council, 20133, Milan, Italy. amadori.m@irea.cnr.it.
² Institute for Electromagnetic Sensing of the Environment, National Research Council, 20133, Milan, Italy.
³ Department of Physics, Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC, Utrecht, The Netherlands.
⁴ Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123, Trento, Italy.

Abstract

Slow and long-term variations of sea surface temperature anomalies have been interpreted as a red-noise response of the ocean surface mixed layer to fast and random atmospheric perturbations. How fast the atmospheric noise is damped depends on the mixed layer depth. In this work we apply this theory to determine the relevant spatial and temporal scales of surface layer thermal inertia in lakes. We fit a first order auto-regressive model to the satellite-derived Lake Surface Water Temperature (LSWT) anomalies in Lake Garda, Italy. The fit provides a time scale, from which we determine the mixed layer depth. The obtained result shows a clear spatial pattern resembling the morphological features of the lake, with larger values (7.18± 0.3 m) in the deeper northwestern basin, and smaller values (3.18 ± 0.24 m) in the southern shallower basin. Such variations are confirmed by in-situ measurements in three monitoring points in the lake and connect to the first Empirical Orthogonal Function of satellite-derived LSWT and chlorophyll-a concentration. Evidence from our case study open a new perspective for interpreting lake-atmosphere interactions and confirm that remotely sensed variables, typically associated with properties of the surface layers, also carry information on the relevant spatial and temporal scales of mixed-layer processes.