Assessment of 19th and 20th century lake and air temperature history in the Peruvian high Andes using biomarkers and lake energy balance modeling

Abstract:

The impacts of climate forcings and internal variability on air temperature in the Peruvian Andes are poorly understood, in part because 20^th and 21^st century temperature data are sparse, especially from high elevations (>4,000 m asl). We present a lake surface temperature reconstruction for the past several centuries using a sediment core from Lake Sibinacocha in the Cordillera Vilcanota (~5000 m asl), southeastern Peru. This record is based on ratios of isoprenoid glycerol dialkyl glycerol tetraethers converted to temperature using the TEX86 paleotemperature proxy. The TEX₈₆ record exhibits strong multidecadal variability that resembles the global temperature record but no overall warming trend despite global and local evidence for strong late 20^th century warming. We use a lake energy balance model, weather station observations, and reanalysis data to investigate three key questions: (1) How do lake temperatures respond to variability in local air temperature? (2) What mechanism(s) control the multidecadal variability in local lake temperatures? and (3) Why is the inferred 20^th century temperature trend ambiguous at this site? Initial results suggest the TEX₈₆ reconstruction correlates with the two longest air temperature records from Cusco, Peru and La Paz, Bolivia. Daily average lake temperature data are accurately reproduced by the lake energy balance model with ERA5-Land hourly input variables, but only after adjusting for a cold bias in the reanalysis data on seasonal and diurnal timescales. Comparison with the TEX₈₆ record provides insight into the impacts of multidecadal climate oscillations on both past and present air temperature in the Andes.