One way of deducing vertical shifts in the altitudinal distribution of Colombian high-altitude páramo environments is by inferring fluctuations in the height of the local freezing level.In our research,we are implementing two complementary approaches to reconstruct Late Pleistocene to Holocene changes in the freezing level height(FLH)in two of the most extensively glacier-covered areas of the northern Andes.We combined remote sensing and field-based geomorphological mapping with time-series reconstruction of changes in the altitude of the 0℃isotherm.Changes in the FLH were based on already-published～30 kyr paleo-reconstructions of sea surface temperatures(SSTs)of the eastern tropical Pacific and the western tropical Atlantic,as well as on reconstructed long-term sea level changes and empirical orthogonal functions of present-day(historical)Indo-Pacific and tropical Atlantic SST anomalies.We also analyzed the probability distribution of air-sea temperature differences and the spatial distribution of grid points with SSTs above the minimum threshold necessary to initiate deep convection.We considered available historical near-surface and free air temperature data of ERA-Interim reanalysis products,General Circulation Model(GCM)simulations,weather stations,and(deployed by our group)digital sensors,to assess the normal Environmental Lapse Rates(ELRs)at the regional to local scale.The combined maps of glacial landforms and our reconstructed FLHs provided us with a well-founded inference of potential past glacier advances,narrowing down the coarse resolution of ice margins suggested by previous research efforts.The extent of the areas with temperatures below the freezing point suggested here for the summits of our main study site exceeds in magnitude the corresponding glacier ice-caps and front advances proposed by previous studies.Conversely,our average lowest altitudes of the FLH for our comparative site are consistently above the main glacier-front advances previously suggested.Our results indicate that,compared to the maximum upward changes that likely took place over the past ca.20,000 years in our two areas of interest,the observed(present-day)upward shifts of the FLH have occurred at a rate that significantly surpasses our inferred rates.Our study helps fill the gaps in understanding past climatic changes and present trends in the region of interest and provides some insights into analyzing the signals of natural and anthropogenic climate change.

Daniel RUIZ-CARRASCAL;Daniel GONZáLEZ-DUQUE;Isabel RESTREPO-CORREA

Department of Ecology,Evolution and Environmental Biology,Columbia University in the City of New York,New York,NY 10027,USA;Department of Civil and Environmental Engineering,Vanderbilt University,400 24th Avenue South,269 Jacobs Hall,Nashville TN 3720,USA;Department of Earth Sciences,Universidad EAFIT,Carrera 49 No.7Sur-50,Medellín,Colombia

山地科学学报（英文版）

[1]Daniel RUIZ-CARRASCAL;Daniel GONZáLEZ-DUQUE;Isabel RESTREPO-CORREA-.Two-tiered reconstruction of Late Pleistocene to Holocene changes in the freezing level height in the largest glacierized areas of the Colombian Andes)[J].山地科学学报（英文版）,2022(03):615-636

ramo,FLH,Lapse,ELRs,FLHs

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