Browsing by Autor "Thomas Condom"

Now showing 1 - 16 of 16

Comment on tc-2022-70
(2022) RubÃ©n Basantes-Serrano; Antoine Rabatel; Bernard Francou; Christian Vincent; Álvaro Soruco; Thomas Condom; Jean Carlo RuÃz
Abstract. We present a comprehensive study of the evolution of the glaciers on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behaviour was observed over the whole period, with two periods of strong mass loss, 1956–1964 (−0.72 m w.e. yr−1) and 1979–1997 (−0.82 m w.e. yr−1), and two periods with slight mass loss, 1965–1978 (0.10 m w.e. yr−1) and 1998–2016 (−0.26 m w.e. yr−1). There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g. maximum and median altitude and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5 and 16) which have been undergoing accelerated disintegration since the 1990s and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers have reacted in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet–dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm–cold conditions observed in the Pacific Ocean represented by the Southern Oscillation index.
Comment on tc-2022-70
(2022) Rubén Basantes-Serrano; Antoine Rabatel; Bernard Francou; Christian Vincent; Álvaro Soruco; Thomas Condom; Jean Carlo RuÃz
We present a comprehensive study of the evolution of the glaciers in the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behavior was observed over the whole period, with two periods of strong mass loss: 1956–1964 and 1979–1997, and two periods with slight mass loss: 1965–1978 and 1997–2016. There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g., maximum and median altitude, and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5, and 16) which have been undergoing accelerated disintegration since the 1990s, and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected in the Antisana G8 in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers react in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet/dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm/cold conditions observed in the Pacific Ocean represented by the Southern Oscillation Index.
Contribution of glacier runoff to water resources of La Paz city, Bolivia (16° S)
(Cambridge University Press, 2015) Álvaro Soruco; Christian Vincent; Antoine Rabatel; Bernard Francou; Emmanuel Thibert; Jean Emmanuel Sicart; Thomas Condom
Abstract The supply of glacier water to La Paz city, Bolivia, between 1963 and 2006 was assessed at annual and seasonal timescales based on the mass-balance quantification of 70 glaciers located within the drainage basins of La Paz. Glaciers contributed ∼15% of water resources at an annual scale (14% in the wet season, 27% in the dry season). Uncertainties in our estimation are related to the assumed constant precipitation (∼0.5% for ice-free areas and up to 6.5% for glaciated areas), the constant runoff coefficient (∼1%), the surface areas of the glaciers and catchments (∼5%) and the mean mass-balance uncertainty of the 21 glaciers used to obtain the mass balance of the 70 glaciers (12% of the total discharge). Despite the loss of 50% of the glacierized area during the study period, runoff at La Paz did not change significantly, showing that increase in ice melt rates compensated for reduction in the surface area of the glaciers. In the future, assuming complete disappearance of the glaciers and no change in precipitation, runoff should diminish by ∼12% at an annual scale, 9% during the wet season and 24% during the dry season.
Deforestation Impacts on Amazon-Andes Hydroclimatic Connectivity
(2021) Juan Pablo Sierra; Clémentine Junquas; Jhan Carlo Espinoza; Hans Segura; Thomas Condom; Marcos Andrade; Jorge Molina‐Carpio; Laura Ticona; Valeria Mardóñez; Luis Blacutt
<title>Abstract</title> Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to the precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation in the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-year high-resolution simulations (2001–2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (~ 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (~ 20–30%) due to a strong reduction in the humidity transport from the Amazon plains toward Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.
Deforestation impacts on Amazon-Andes hydroclimatic connectivity
(2021) Juan Pablo Sierra; Jhan Carlo Espinoza; Clémentine Junquas; Jan Polcher‬; Miguel Saavedra; Jorge Molina‐Carpio; Marcos Andrade; Thomas Condom; Laura Ticona
&lt;p&gt;The Amazon rainforest is a key component of the climate system and one of the main planetary evapotranspiration sources. Over the entire Amazon basin, strong land-atmosphere feedbacks cause almost one third of the regional rainfall to be transpired by the local rainforest. Maximum precipitation recycling ratio takes place on the southwestern edge of the Amazon basin (a.k.a. Amazon-Andes transition region), an area recognized as the rainiest and biologically richest of the whole watershed. Here, high precipitation rates lead to large values of runoff per unit area providing most of the sediment load to Amazon rivers. As a consequence, the transition region can potentially be very sensitive to Amazonian forest loss. In fact, recent acceleration in deforestation rates has been reported over tropical South America. These sustained land-cover changes can alter the regional water and energy balances, as well as the regional circulation and rainfall patterns. In this sense, the use of regional climate models can help to understand the possible impacts of deforestation on the Amazon-Andes zone.&lt;/p&gt;&lt;p&gt;This work aims to assess the projected Amazonian deforestation effects on the moisture transport and rainfall behavior over tropical South America and the Amazon-Andes transition region. We perform 10-year austral summer simulations with the Weather Research and Forecasting model (WRF) using 3 one-way nested domains. Our finest domain is located over the south-western part of the basin, comprising two instrumented Andean Valleys (Zongo and Coroico river Valleys). Convective permitting high horizontal resolution (1km) is used over this domain. The outcomes presented here enhance the understanding of biosphere-atmosphere coupling and its deforestation induced disturbances.&lt;/p&gt;
Deforestation impacts on Amazon-Andes hydroclimatic connectivity
(Springer Science+Business Media, 2021) Juan Pablo Sierra; Clémentine Junquas; Jhan Carlo Espinoza; Hans Segura; Thomas Condom; Marcos Andrade; Jorge Molina‐Carpio; Laura Ticona; Valeria Mardóñez; Luis Blacutt
Diagenetic production, accumulation and sediment-water exchanges of methylmercury in contrasted sediment facies of Lake Titicaca (Bolivia)
(Elsevier BV, 2020) Stéphane Guédron; Stéphane Audry; Darío Achá; Sylvain Bouchet; David Point; Thomas Condom; Carlos Heredia; Sylvain Campillo; Pascale A. Baya; Alexis Groleau
Données isotopiques (8786/Sr) et changements hydrologiques depuis 15 000 ans sur l'Altiplano andin
(Taylor & Francis, 2002) Anne Coudrain; M. Loubet; Thomas Condom; Amal Talbi; Pierre Ribstein; Bernard Pouyaud; Jorge Quintanilla; Claudine Dieulin; Bernard Dupré
Résumé Actuellement, le bassin sud (17°-22°S, 126 000 km2) de l'Altiplano reçoit environ 39.4 × 109 m3 an−1 d'eau, dont 4% proviennent du bassin nord (14°-17°S) par le Rio Desaguadero. Le rapport 87Sr/86Sr des écoulements de surface actuels présentent des valeurs distinctes sur les deux bassins permettant d'utiliser ce traceur pour reconstituer des conditions hydrologiques passées contrastées du bassin sud. Pour la période aride de 10 000 à 2000 ans BP, les données acquises et la modélisation du transport de strontium dans un aquifàre renforcent les Hypothàses d'une valeur des précipitations de 80% de l'actuel et de l'absence d'alimentation significative du bassin sud par le Rio Desaguadero. Pour les hauts niveaux d'eau de la phase lacustre Tauca, vers 15 000 ans BP, les données hydrologiques et isotopiques indiquent que pour une alimentation totale estimée à 110 109 m1 an1 les apports du bassin nord pouvaient être limités à 5%.
New insights into the decadal variability in glacier volume of a tropical ice cap, Antisana (0°29′ S, 78°09′ W), explained by the morpho-topographic and climatic context
(Copernicus Publications, 2022) Rubén Basantes-Serrano; Antoine Rabatel; Bernard Francou; Christian Vincent; Álvaro Soruco; Thomas Condom; Jean Carlo Ruíz
Abstract. We present a comprehensive study of the evolution of the glaciers on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behaviour was observed over the whole period, with two periods of strong mass loss, 1956–1964 (−0.72 m w.e. yr−1) and 1979–1997 (−0.82 m w.e. yr−1), and two periods with slight mass loss, 1965–1978 (0.10 m w.e. yr−1) and 1998–2016 (−0.26 m w.e. yr−1). There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g. maximum and median altitude and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5 and 16) which have been undergoing accelerated disintegration since the 1990s and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers have reacted in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet–dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm–cold conditions observed in the Pacific Ocean represented by the Southern Oscillation index.
New insights into the decadal variability in glacier volume of an iconic tropical ice-cap explained by the morpho-climatic context, Antisana, (0°29’ S, 78°09’ W)
(2022) Rubén Basantes-Serrano; Antoine Rabatel; Bernard Francou; Christian Vincent; Álvaro Soruco; Thomas Condom; Jean Carlo Ruíz
Abstract. We present a comprehensive study of the evolution of the glaciers in the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behavior was observed over the whole period, with two periods of strong mass loss: 1956–1964 and 1979–1997, and two periods with slight mass loss: 1965–1978 and 1997–2016. There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g., maximum and median altitude, and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5, and 16) which have been undergoing accelerated disintegration since the 1990s, and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected in the Antisana G8 in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers react in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet/dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm/cold conditions observed in the Pacific Ocean represented by the Southern Oscillation Index.
Regional hydro-climatic changes in the Southern Amazon Basin (Upper Madeira Basin) during the 1982–2017 period
(Elsevier BV, 2019) Jhan Carlo Espinoza; Anna A. Sörensson; Josyane Ronchail; Jorge Molina‐Carpio; Hans Segura; Omar Gutierrez‐Cori; Romina Ruscica; Thomas Condom; Sly Wongchuig
Retroceso del glaciar del Carihuairazo y sus implicaciones en la comunidad de Cunucyacu
(Politecnica Salesiana University, 2024) David Hidalgo; Jean Carlos Ruiz; Luis Maisincho; Bolívar Cáceres; Verónica Crespo‐Pérez; Christian Domínguez; David Piedra; Thomas Condom; Marcos Villacís
El retroceso de los glaciares es una realidad en toda la cordillera de los Andes, sobre todo en montañas de baja altitud. Uno de estos casos es la pérdida de la masa de hielo remanente en el Carihuairazo (Tungurahua, Ecuador), que en los últimos años ha experimentado un retroceso considerable. En esta investigación se intenta caracterizar el retroceso de este glaciar y su implicación en la comunidad más cercana (Cunucyacu) por medio de la aplicación de una metodología de múltiples fuentes que incluye la recopilación de aerofotografías del glaciar, datos de estaciones meteorológicas cercanas, uso de datos de reanálisis del clima global, entrevistas a miembros de la comunidad y a andinistas que trabajan y frecuentan la zona. Para caracterizar la evolución de la masa del glaciar aplicamos un modelo hidroglaciológico que usa como entrada datos de series meteorológicas y cuyos parámetros fueron calibrados con el registro fotográfico del contorno del glaciar. Como resultados se puede evidenciar una pérdida del glaciar para el 2021 equivalente al 99% de su superficie en 1956 (0.34 ). El modelo logra simular la variación del área del glaciar durante 67 años, en donde se observa un decrecimiento continuo del glaciar a partir de 1978, con cortos periodos de recuperación y equilibrio, en donde la temperatura es la variable que mejor explica el retroceso del glaciar. El modelo no logra considerar el efecto de factores externos como el caso de la erupción del volcán Tungurahua que podría favorecer el retroceso del glaciar. El glaciar Carihuairazo se encuentra en una situación de inevitable desaparición y revela las vulnerabilidades de las comunidades que se enfrentan a este fenómeno como consecuencia del cambio climático.
Technical note: A low-cost albedometer for snow and ice measurements – theoretical results and application on a tropical mountain in Bolivia
(Copernicus Publications, 2018) Thomas Condom; Marie Dumont; Lise Mourre; Jean Emmanuel Sicart; Antoine Rabatel; Alessandra Viani; Álvaro Soruco
Abstract. This study presents a new instrument called a low-cost albedometer (LCA) composed of two illuminance sensors that are used to measure in situ incident and reflected illuminance values on a daily timescale. The ratio between reflected vs. incident illuminances is called the albedo index and can be compared with actual albedo values. Due to the shape of the sensor, the direct radiation for zenith angles ranging from 55 to 90∘ is not measured. The spectral response of the LCA varies with the solar irradiance wavelengths within the range 0.26 to 1.195 µm, and the LCA detects 85 % of the total spectral solar irradiance for clear sky conditions. We first consider the theoretical results obtained for 10 different ice and snow surfaces with clear sky and cloudy sky incident solar irradiance that show that the LCA spectral response may be responsible for an overestimation of the theoretical albedo values by roughly 9 % at most. Then, the LCA values are compared with two “traditional” albedometers, which are CM3 pyranometers (Kipp &amp; Zonen), in the shortwave domain from 0.305 to 2.800 µm over a 1-year measurement period (2013) for two sites in a tropical mountainous catchment in Bolivia. One site is located on the Zongo Glacier (i.e., snow and ice surfaces) and the second one is found on the crest of the lateral moraine (bare soil and snow surfaces), which present a horizontal surface and a sky view factor of 0.98. The results, at daily time steps (256 days), given by the LCA are in good agreement with the classic albedo measurements taken with pyranometers with R2=0.83 (RMSD = 0.10) and R2=0.92 (RMSD = 0.08) for the Zongo Glacier and the right-hand side lateral moraine, respectively. This demonstrates that our system performs well and thus provides relevant opportunities to document spatiotemporal changes in the surface albedo from direct observations at the scale of an entire catchment at a low cost. Finally, during the period from September 2015 to June 2016, direct observations were collected with 15 LCAs on the Zongo Glacier and successfully compared with LANDSAT images showing the surface conditions of the glacier (i.e., snow or ice). This comparison illustrates the efficiency of this system to monitor the daily time step changes in the snow and ice coverage distributed on the glacier. Despite the limits imposed by the angle view restrictions, the LCA can be used between 45∘ N and 45∘ S during the ablation season (spring and summer) when the melt rate related to the albedo is the most important.
Technical note: A low-cost albedometer for snow and ice measurements –Theoretical results and application on a tropical mountain in Bolivia
(2018) Thomas Condom; Marie Dumont; Lise Mourre; Jean Emmanuel Sicart; Antoine Rabatel; Alessandra Viani; Alavaro Soruco
Abstract. This study presents a new instrument called a low-cost albedometer (LCA) composed of two illuminance sensors that are used to measure in-situ incident and reflected illuminance values on a daily timescale. The ratio between reflected vs. incident illuminances is called the albedo index and can be compared with actual albedo values. Due to the shape of the sensor, the direct radiation for zenith angles ranging from 55° to 90° is not measured. The spectral response of the LCA varies with the solar irradiance wavelengths within the range 0.26 to 1.195 µm, and the LCA detects 85 % of the total spectral solar irradiance for clear sky conditions. We first consider the theoretical results obtained for 10 different ice and snow surfaces with clear sky and cloudy sky incident solar irradiance that show that the LCA spectral response may be responsible for an overestimation of the theoretical albedo values by roughly 9 % at most. Then, the LCA values are compared with two classical albedometers over a one-year measurement period (2013) for two sites in a tropical mountainous catchment in Bolivia. One site is located on the Zongo Glacier (i.e. snow and ice surfaces) and the second one is found on the right-hand side lateral moraine (bare soil and snow surfaces). The results, at daily time steps (256 days), given by the LCA are in good agreement with the classic albedo measurements taken with pyranometers with R2 = 0.83 (RMSD = 0.10) and R2 = 0.92 (RMSD = 0.08) for the Zongo Glacier and the right-hand side lateral moraine, respectively. This demonstrates that our system performs well and thus provides relevant opportunities to document spatio-temporal changes in the surface albedo from direct observations at the scale of an entire catchment at a low cost. Finally, during the period from September 2015 to June 2016, direct observations were collected with 15 LCAs on the Zongo Glacier and successfully compared with LANDSAT images showing the surface state of the glacier (i.e. snow or ice). This comparison illustrates the efficiency of this system to monitor the daily time step changes in the snow/ice coverage distributed on the glacier.
Technical Note: Glacial influence in tropical mountain hydrosystems evidenced by the diurnal cycle in water levels
(Copernicus Publications, 2013) Sophie Cauvy‐Fraunié; Thomas Condom; Antoine Rabatel; Marcos Villacís; Dean Jacobsen; Olivier Dangles
Abstract. Worldwide, the rapid shrinking of glaciers in response to ongoing climate change is modifying the glacial meltwater contribution to hydrosystems in glacierized catchments. Determining the influence of glacial runoff to streams is therefore of critical importance to evaluate potential impact of glacier retreat on water quality and aquatic biota. This task has challenged both glacier hydrologists and ecologists over the last 20 yr due to both structural and functional complexity of the glacier–stream system interface. Here we propose quantifying the diurnal cycle amplitude of the streamflow to determine the glacial influence in glacierized catchments. We performed water-level measurements using water pressure loggers over 10 months at 30 min time steps in 15 stream sites in 2 glacier-fed catchments in the Ecuadorian Andes (> 4000 m a.s.l.) where no perennial snow cover is observed outside the glaciers. For each stream site, we performed wavelet analyses on water-level time series, determined the scale-averaged wavelet power spectrum at 24 h scale and defined three metrics, namely the power, frequency and temporal clustering of the diurnal flow variation. The three metrics were then compared to the percentage of the glacier cover in the catchments, a metric of glacial influence widely used in the literature. As expected, we found that the diurnal variation power of glacier-fed streams decreased downstream with the addition of non-glacial tributaries. We also found that the diurnal variation power and the percentage of the glacier cover in the catchment were significantly positively correlated. Furthermore, we found that our method permits the detection of glacial signal in supposedly non-glacial sites, thereby revealing glacial meltwater resurgence. While we specifically focused on the tropical Andes in this paper, our approach to determine glacial influence may have potential applications in temperate and arctic glacierized catchments. The measure of diurnal water amplitude therefore appears as a powerful and cost-effective tool to understand the hydrological links between glaciers and hydrosystems better and assess the consequences of rapid glacier shrinking.
The 2022-23 drought in the South American Altiplano: ENSO effects on moisture flux in the western Amazon during the pre-wet season
(Elsevier BV, 2024) Ricardo A. Gutiérrez; Jhan Carlo Espinoza; Waldo Lavado‐Casimiro; Clémentine Junquas; Jorge Molina‐Carpio; Thomas Condom; José A. Marengo