Andres Rivera - Academia.edu (original) (raw)

Papers by Andres Rivera

Research paper thumbnail of Characteristics of tide-water calving at Glaciar San Rafael, Chile

Journal of Glaciology, 1995

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Research paper thumbnail of Geomorphological evidence for variations of the North Patagonian Icefield during the Holocene

Geomorphology, 2005

Elucidating the timing and extent of former glacier fluctuations is important because of the pala... more Elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies. Here we present new geomorphological evidence of the patterns of glacier behaviour around the North Patagonian Icefield during the Holocene. Mapping is based on visual interpretation of Landsat 7 ETM+ and Terra ASTER satellite images, including the contemporary glaciers, areas of ice-scoured bedrock, trimlines, glacial lineations, terminal moraines, sandur and fluvial sediments, deltas and ice-contact deposits and alluvial fans. Recession of the icefield is marked by three distinct moraine sets. These moraine sets are interpreted as marking terminal positions related to the bLittle Ice AgeQ and two preceding, but as yet undated, phases of Holocene glacier expansion. Large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features, reflecting topographic limits to glacier expansion, indicating that caution is required in the interpretation of previous 14 C dates obtained from these moraines. There are strong contrasts in the patterns of glacier behaviour between the east and west sides of the North Patagonian Icefield, which cannot be attributed simply to an east/west differential in the rates of change of atmospheric temperature and precipitation. We argue here that glacier response to first-order climate forcing is tempered by second-order controls introduced by regional-scale topographic effects, notably glacier drainage basin extent and area, topographic controls on glacier snout morphology and differences in terminal environment (calving/non-calving) during glacier recession.

Research paper thumbnail of Characteristics of tide-water calving at Glaciar San Rafael, Chile

Journal of Glaciology, 1995

RefDoc Refdoc est un service / is powered by. ...

Research paper thumbnail of Geomorphological evidence for variations of the North Patagonian Icefield during the Holocene

Geomorphology, 2005

Elucidating the timing and extent of former glacier fluctuations is important because of the pala... more Elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies. Here we present new geomorphological evidence of the patterns of glacier behaviour around the North Patagonian Icefield during the Holocene. Mapping is based on visual interpretation of Landsat 7 ETM+ and Terra ASTER satellite images, including the contemporary glaciers, areas of ice-scoured bedrock, trimlines, glacial lineations, terminal moraines, sandur and fluvial sediments, deltas and ice-contact deposits and alluvial fans. Recession of the icefield is marked by three distinct moraine sets. These moraine sets are interpreted as marking terminal positions related to the bLittle Ice AgeQ and two preceding, but as yet undated, phases of Holocene glacier expansion. Large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features, reflecting topographic limits to glacier expansion, indicating that caution is required in the interpretation of previous 14 C dates obtained from these moraines. There are strong contrasts in the patterns of glacier behaviour between the east and west sides of the North Patagonian Icefield, which cannot be attributed simply to an east/west differential in the rates of change of atmospheric temperature and precipitation. We argue here that glacier response to first-order climate forcing is tempered by second-order controls introduced by regional-scale topographic effects, notably glacier drainage basin extent and area, topographic controls on glacier snout morphology and differences in terminal environment (calving/non-calving) during glacier recession.

Research paper thumbnail of A review of remote sensing methods for glacier mass balance determination

Global and Planetary Change, 2007

Airborne and satellite remote sensing is the only practical approach for deriving a wide area, re... more Airborne and satellite remote sensing is the only practical approach for deriving a wide area, regional assessment of glacier mass balance. A number of remote sensing approaches are possible for inferring the mass balance from some sort of proxy estimate. Here, we review the key methods relevant, in particular to Andean glaciers, discussing their strengths and weaknesses, and data sets that could be more fully exploited. We also consider future satellite missions that will provide advances in our observational capabilities. The methods discussed include observation of elevation changes, estimation of ice flux, repeat measurement of changes in spatial extent, snowline elevation and accumulation-ablation area ratio estimation. The methods are illustrated utilising a comprehensive review of results obtained from a number of studies of South American glaciers, focusing specifically on the Patagonian Icefields. In particular, we present some new results from Glaciar Chico, Southern Patagonian Icefield, Chile, where a variety of different satellite and in-situ data have been combined to estimate mass balance using a geodetic or elevation change approach over about a 25 yr period.

Research paper thumbnail of A review of remote sensing methods for glacier mass balance determination

Global and Planetary Change, 2007

Airborne and satellite remote sensing is the only practical approach for deriving a wide area, re... more Airborne and satellite remote sensing is the only practical approach for deriving a wide area, regional assessment of glacier mass balance. A number of remote sensing approaches are possible for inferring the mass balance from some sort of proxy estimate. Here, we review the key methods relevant, in particular to Andean glaciers, discussing their strengths and weaknesses, and data sets that could be more fully exploited. We also consider future satellite missions that will provide advances in our observational capabilities. The methods discussed include observation of elevation changes, estimation of ice flux, repeat measurement of changes in spatial extent, snowline elevation and accumulation-ablation area ratio estimation. The methods are illustrated utilising a comprehensive review of results obtained from a number of studies of South American glaciers, focusing specifically on the Patagonian Icefields. In particular, we present some new results from Glaciar Chico, Southern Patagonian Icefield, Chile, where a variety of different satellite and in-situ data have been combined to estimate mass balance using a geodetic or elevation change approach over about a 25 yr period.

Research paper thumbnail of Jaramillo – Descentralizacion Salud-Mexico Access to medical emergency services in Medellín during 2006

Objetivos Describir el acceso y la oportunidad de la atención de las urgencias médicas en Medellí... more Objetivos Describir el acceso y la oportunidad de la atención de las urgencias médicas en Medellín, 2006. Materiales y Métodos Se realizó un estudio descriptivo en 27 servicios de urgencias de Instituciones Prestadoras de Servicios de Salud de tercero, segundo y primer nivel de atención durante una semana continua. A todas las personas admitidas se les realizó seguimiento hasta el egreso del servicio. Las siguientes variables fueron descritas: cacterísticas de persona, tiempos espera, presencia de trauma, consulta previa a un servicio de urgencias en las últimas 48 horas por la misma causa, referencia y egreso. En aquellas personas no admitidas se estudiaron las causas de no admisión. Resultados De 9 703 pacientes que visitaron los servicios de urgencias, 8 703 (89,4 %) fueron admitidos, 13,8 % habían consultado en las últimas 48 horas a un servicio de urgencias por la misma causa y el 10,5 % tuvieron remisión previa. Fue superior el tiempo espera en los servicios de urgencias de primer nivel (40,2 minutos). De las 1 027 (10,6 %) personas que no fueron admitidas, el 62,6 % fue debido a que la consulta no fue considerada urgente por el personal hospitalario, seguido del 16 % por no pertenecer a la red a la cual cotizaba. Conclusiones En los servicios de urgencias de Medellín existen barreras de acceso. El acceso inadecuado de acuerdo al tipo y gravedad de la urgencia y la deficiente la articulación de los niveles de atención, soporta la necesidad una red de urgencias en la ciudad.

Research paper thumbnail of Characteristics of tide-water calving at Glaciar San Rafael, Chile

Journal of Glaciology, 1995

RefDoc Refdoc est un service / is powered by. ...

Research paper thumbnail of Geomorphological evidence for variations of the North Patagonian Icefield during the Holocene

Geomorphology, 2005

Elucidating the timing and extent of former glacier fluctuations is important because of the pala... more Elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies. Here we present new geomorphological evidence of the patterns of glacier behaviour around the North Patagonian Icefield during the Holocene. Mapping is based on visual interpretation of Landsat 7 ETM+ and Terra ASTER satellite images, including the contemporary glaciers, areas of ice-scoured bedrock, trimlines, glacial lineations, terminal moraines, sandur and fluvial sediments, deltas and ice-contact deposits and alluvial fans. Recession of the icefield is marked by three distinct moraine sets. These moraine sets are interpreted as marking terminal positions related to the bLittle Ice AgeQ and two preceding, but as yet undated, phases of Holocene glacier expansion. Large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features, reflecting topographic limits to glacier expansion, indicating that caution is required in the interpretation of previous 14 C dates obtained from these moraines. There are strong contrasts in the patterns of glacier behaviour between the east and west sides of the North Patagonian Icefield, which cannot be attributed simply to an east/west differential in the rates of change of atmospheric temperature and precipitation. We argue here that glacier response to first-order climate forcing is tempered by second-order controls introduced by regional-scale topographic effects, notably glacier drainage basin extent and area, topographic controls on glacier snout morphology and differences in terminal environment (calving/non-calving) during glacier recession.

Research paper thumbnail of Characteristics of tide-water calving at Glaciar San Rafael, Chile

Journal of Glaciology, 1995

RefDoc Refdoc est un service / is powered by. ...

Research paper thumbnail of Geomorphological evidence for variations of the North Patagonian Icefield during the Holocene

Geomorphology, 2005

Elucidating the timing and extent of former glacier fluctuations is important because of the pala... more Elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies. Here we present new geomorphological evidence of the patterns of glacier behaviour around the North Patagonian Icefield during the Holocene. Mapping is based on visual interpretation of Landsat 7 ETM+ and Terra ASTER satellite images, including the contemporary glaciers, areas of ice-scoured bedrock, trimlines, glacial lineations, terminal moraines, sandur and fluvial sediments, deltas and ice-contact deposits and alluvial fans. Recession of the icefield is marked by three distinct moraine sets. These moraine sets are interpreted as marking terminal positions related to the bLittle Ice AgeQ and two preceding, but as yet undated, phases of Holocene glacier expansion. Large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features, reflecting topographic limits to glacier expansion, indicating that caution is required in the interpretation of previous 14 C dates obtained from these moraines. There are strong contrasts in the patterns of glacier behaviour between the east and west sides of the North Patagonian Icefield, which cannot be attributed simply to an east/west differential in the rates of change of atmospheric temperature and precipitation. We argue here that glacier response to first-order climate forcing is tempered by second-order controls introduced by regional-scale topographic effects, notably glacier drainage basin extent and area, topographic controls on glacier snout morphology and differences in terminal environment (calving/non-calving) during glacier recession.

Research paper thumbnail of A review of remote sensing methods for glacier mass balance determination

Global and Planetary Change, 2007

Airborne and satellite remote sensing is the only practical approach for deriving a wide area, re... more Airborne and satellite remote sensing is the only practical approach for deriving a wide area, regional assessment of glacier mass balance. A number of remote sensing approaches are possible for inferring the mass balance from some sort of proxy estimate. Here, we review the key methods relevant, in particular to Andean glaciers, discussing their strengths and weaknesses, and data sets that could be more fully exploited. We also consider future satellite missions that will provide advances in our observational capabilities. The methods discussed include observation of elevation changes, estimation of ice flux, repeat measurement of changes in spatial extent, snowline elevation and accumulation-ablation area ratio estimation. The methods are illustrated utilising a comprehensive review of results obtained from a number of studies of South American glaciers, focusing specifically on the Patagonian Icefields. In particular, we present some new results from Glaciar Chico, Southern Patagonian Icefield, Chile, where a variety of different satellite and in-situ data have been combined to estimate mass balance using a geodetic or elevation change approach over about a 25 yr period.

Research paper thumbnail of A review of remote sensing methods for glacier mass balance determination

Global and Planetary Change, 2007

Airborne and satellite remote sensing is the only practical approach for deriving a wide area, re... more Airborne and satellite remote sensing is the only practical approach for deriving a wide area, regional assessment of glacier mass balance. A number of remote sensing approaches are possible for inferring the mass balance from some sort of proxy estimate. Here, we review the key methods relevant, in particular to Andean glaciers, discussing their strengths and weaknesses, and data sets that could be more fully exploited. We also consider future satellite missions that will provide advances in our observational capabilities. The methods discussed include observation of elevation changes, estimation of ice flux, repeat measurement of changes in spatial extent, snowline elevation and accumulation-ablation area ratio estimation. The methods are illustrated utilising a comprehensive review of results obtained from a number of studies of South American glaciers, focusing specifically on the Patagonian Icefields. In particular, we present some new results from Glaciar Chico, Southern Patagonian Icefield, Chile, where a variety of different satellite and in-situ data have been combined to estimate mass balance using a geodetic or elevation change approach over about a 25 yr period.

Research paper thumbnail of Jaramillo – Descentralizacion Salud-Mexico Access to medical emergency services in Medellín during 2006

Objetivos Describir el acceso y la oportunidad de la atención de las urgencias médicas en Medellí... more Objetivos Describir el acceso y la oportunidad de la atención de las urgencias médicas en Medellín, 2006. Materiales y Métodos Se realizó un estudio descriptivo en 27 servicios de urgencias de Instituciones Prestadoras de Servicios de Salud de tercero, segundo y primer nivel de atención durante una semana continua. A todas las personas admitidas se les realizó seguimiento hasta el egreso del servicio. Las siguientes variables fueron descritas: cacterísticas de persona, tiempos espera, presencia de trauma, consulta previa a un servicio de urgencias en las últimas 48 horas por la misma causa, referencia y egreso. En aquellas personas no admitidas se estudiaron las causas de no admisión. Resultados De 9 703 pacientes que visitaron los servicios de urgencias, 8 703 (89,4 %) fueron admitidos, 13,8 % habían consultado en las últimas 48 horas a un servicio de urgencias por la misma causa y el 10,5 % tuvieron remisión previa. Fue superior el tiempo espera en los servicios de urgencias de primer nivel (40,2 minutos). De las 1 027 (10,6 %) personas que no fueron admitidas, el 62,6 % fue debido a que la consulta no fue considerada urgente por el personal hospitalario, seguido del 16 % por no pertenecer a la red a la cual cotizaba. Conclusiones En los servicios de urgencias de Medellín existen barreras de acceso. El acceso inadecuado de acuerdo al tipo y gravedad de la urgencia y la deficiente la articulación de los niveles de atención, soporta la necesidad una red de urgencias en la ciudad.