Modelling surface mass balance and water discharge of tropical glaciers The case study of three glaciers in La Cordillera Blanca of Perú Presented by: MSc. Maria Fernanda Lozano Supervised by: Prof. Dr. rer. nat. Manfred Koch

Content Problem statement Objectives Study area Available data (temperature, precipitation, mass balance measurements, radiation data) Filling data gaps Methods  Energy balance Model  Temperature Index Model Modelling mass balance under climate change simulation by REMO

Problem statement Changes in climate Alteration of mass balance Front advance or Retreatment Changes in discharge Identification of causes what will happen Energy balance models Temperature Index models Not large records Data gaps Estimation of Future discharge

Objectives Contribute to the understanding of glacier climate interaction in tropical areas. Foresee the possible variation on surface water discharge due to climate change. Evaluate historical trends of hidroclimatic time series. Fill the gaps in time series Simulate the dynamic of the mass balance and runoff with a Energy Balance Model (4 years) Simulate runoff of the glaciers with a Temperature Index model. Examine the sensitivity of stream-flow of surface water resources under future climate scenarios of global warming

Study Area

Available data

Time series available in glaciersTime series available in related basins

Temperature and precipitation

Mass balance measurements

Retreatment of the Yanamarey glacier since

Glacier front variation in glaciers of the Cordillera Blanca

Energy data in Artesonraju

Filling gaps in time series Multilinear regression STL

Energy balance model (Hock) Distributed model. Works in a subdiurnal or diurnal temporal resolution. Solves the energy balance equation on the glacierized area (calculation per each grid of DTM). Calculates water discharge from the melting of three areas (firn, snow and ice) and the liquid precipitation. Accounts for the spatial distribution of topographic shading. Calculates individual energy balance components ACCUMULATION: Precipitation (temperature) ABLATION Melting and Sublimation

Energy balance model (Hock) Global radiation Main stationExtrapolation 1.Interpolation of G directly 2. Separating G into direct and diffuse radiation considering terrain effects Amounts of diffuse radiation Cloud Cover Gs/Ics Gg=Icg*(Gs/Ics) the radio of global radiation to top of the atmosphere G/I ToA Is=Gs-Ds Ig=Icg*(Is/Ics) Direct radiation Diffuse radiation

Energy balance model (Hock) Albedo Extrapolation Snow Albedo Variable: Number of days since last snowfall Air temperature Assumed constant according to the surface Ice Albedo Variable: Assumed increase of 3%(100m-1) Account for the tendency of debris to accumulate towards the glacier. Variable for snow and ice.

Energy balance model (Hock) Long inc. radiation Long out. radiation Main stationExtrapolation It requires the estimation of Lo at climate station and it is assumed invariant for all grids. Lsky: Lterrain: Linc in each grid is calculated as the sum of Lsky and Lterrain in each grid. Direct measurements of longwave outgoing radiation Linear decrease with increasing elevation when surface temperature is negative, if temperature is 0 Lout is spatially constant

Energy balance model (Hock) Sensible heat Latent heat Qh proportional to Temperature (Tz) and Wind speed (zu) Calculated from the aerodynamic approach QL proportional to vapour pressure (ez) and Wind speed (zu) LLatent heat of evaporation or sublimation ρ density of air Po mean atmospheric pressure at the sea level Cp specific heat capacity of air k Karman´s constant To surface temperature Eo vapor pressure of the surface Zow, zoT and zoe are the roughness lengths fro logarithmic profiles of wind speed, temperature and water vapor

Energy balance model (Hock) Conditions Daily resolution No separation of direct and diffuse radiation Albedo constant Snow water equivalent interpolated with linear interpolation.

Temperature Index Model (Hock) Melt=(DDF/24)*T(timestep) T>0 Melt=0 T<=0 Melt=(MF/24+ rsnow/ice*I)*T(timestep) T>0 Melt=0 T<=0 Melt=(MF+rsnow/ice*I*Globs/Is)*T(timestep) T>0 Melt=0T<=0 DDF= Degree day factor mm/oCdía MF= Melt factor mm/h K rsnow/ice= radfactorice mm m2/WhK Melting is related to the positive air temperatures and the amount of time that this temperature exceeds the melting point. This relation uses a factor of proportionality (DDF) which shows the decrease of water content in the snow cover or ice by 1°C above freezing in 24 hours. Incorporates clear sky solar radiation (I) accounts for the spatial topographic variability Incorporates global measured radiation Which account for deviations on clear sky conditions

Temperature Index Model (Hock)

Simulation of glacier discharge in future scenarios of climate change MPI Regional Climate Model Remo Horizontal Resolution 50Km x 50 Km (0.44°x 0.44°) Variables: Temperature, surface pressure, horizontal wind components, precipitation and humidity. Domain. South América Time step: 240 s Forcing Data: ERA Interim Simulation Period: Future Simulation: until 2100 (in process)

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Mass Balance Year of positive mass balanceYear of negative mass balance