| Popis: |
This dissertation comprises of a multi-part investigation into the impacts and contributions of debris-covered glaciers to the surface hydrology of the Cordillera Blanca, Peru. Due to the circumstances surrounding the global pandemic, the originally planned in situ dataset was not collected; however, following a pivot in research goals and objectives, field collected (prior to 2020) streamflow and water quality data, and remotely sensed imagery were used to answer the slightly broadened questions of this dissertation. First, without a specific focus on debris-covered glacier catchments, long-term hydrological shifts were identified throughout the past 70-years, and short-term daily fluctuations were assessed throughout the Rio Santa watershed. Multiple change points were identified to have occurred over the historical record, with the most recent changes in the 2000s that indicate lower rates of loss in discharge now compared to prior decades. High-temporal resolution discharge data is presented which provides evidence that diurnal changes in streamflow are driven by seasonal fluctuations and have not undergone significant shifts in timing or amplitude during the past 14-years. Second, high-resolution satellite imagery was used to calculate the spatial and temporal changes and estimate volumes of supraglacial ponds on the surface of debris-covered glaciers for the first time across the Peruvian Andes. Expanding the study area beyond the Cordillera Blanca allowed for the opportunity to test patterns in debris-covered glacier ponds more broadly and place the Cordillera Blanca in a regional context. From these analyses, debris-covered glacier pond area maxima were recorded to have occurred in 2012 and 2013 across the Peruvian Andes. Furthermore, as minimum temperatures significantly rose over the past 11 years, a decrease in total supraglacial pond area was measured. Finally, water volume estimates provide strong indications that debris-covered glaciers contribute significant amounts of water to surface streamflow in the upper tributaries of the Rio Santa. Third, an extensive hydrochemical dataset containing isotopic and ionic composition data from stream water was evaluated to characterize and quantify the differences between debris-covered glacier outflow streams in relation to their clean ice counterparts for the first time in a tropical high mountain region. Isotopic values below debris-covered glaciers were found to be consistently depleted in relation to their debris-free counterparts, indicating there are likely fewer melt/freeze cycles found within the debris-covered portions of these glaciers. Hydrochemical analyses provided further evidence that debris-covered glaciers display unique ionic and isotopic characteristics in relation to debris-free glaciers within the same mountain range. Overall, the findings from these studies provide compelling evidence that debris-covered glaciers contribute significant quantities of streamflow and produce less chemically altered waters to the surface hydrological system, specifically in the upper valleys where they are present, within the Cordillera Blanca. |
