Jeffrey M. McKenzie

Climate Change and Tropical Andean Glacier Recession: Evaluating Hydrologic Changes and Livelihood Vulnerability in the Cordillera Blanca, Peru

Climate change is forcing dramatic glacier mass loss in the Cordillera Blanca, Peru, resulting in hydrologic transformations across the Rio Santa watershed and increasing human vulnerability. This article presents results from two years of transdisciplinary collaborative research evaluating the complex relationships between coupled environmental and social change in the region. First, hydrologic results suggest there has been an average increase of 1.6 (± 1.1) percent in the specific discharge of the more glacier-covered catchments (>20 percent glacier area) as a function of changes in stable isotopes of water (δ18O and δ2H) from 2004 to 2006. Second, there is a large (mean 60 percent) component of groundwater in dry season discharge based on results from the hydrochemical basin characterization method. Third, findings from extensive key interviews and seventy-two randomly sampled household interviews within communities located in two case study watersheds demonstrate that a large majority of households perceive that glacier recession is proceeding very rapidly and that climate change–related impacts are affecting human vulnerability across multiple shifting vectors including access to water resources, agro-pastoral production, and weather variability.

New Geographies of Water and Climate Change in Peru: Coupled Natural and Social Transformations in the Santa River Watershed

Projections of future water shortages in the worlds glaciated mountain ranges have grown increasingly dire. Although water modeling research has begun to examine changing environmental parameters, the inclusion of social scenarios has been very limited. Yet human water use and demand are vital for long-term adaptation, risk reduction, and resource allocation. Concerns about future water supplies are particularly pronounced on Perus arid Pacific slope, where upstream glacier recession has been accompanied by rapid and water-intensive economic development. Models predict water shortages decades into the future, but conflicts have already arisen in Perus Santa River watershed due to either real or perceived shortages. Modeled thresholds do not align well with historical realities and therefore suggest that a broader analysis of the combined natural and social drivers of change is needed to more effectively understand the hydrologic transformation taking place across the watershed. This article situates these new geographies of water and climate change in Peru within current global change research discussions to demonstrate how future coupled research models can inform broader scale questions of hydrologic change and water security across watersheds and regions. We provide a coupled historical analysis of glacier recession in the Cordillera Blanca, declining Santa River discharge, and alpine wetland contraction. We also examine various water withdrawal mechanisms, including smallholder agriculture, mining, potable water use, hydroelectric power generation, and coastal irrigation. We argue that both ecological change and societal forces will play vital roles in shaping the future of water resources and water governance in the region.

Permafrost thaw in a nested groundwater-flow system

Groundwater flow in cold regions containing permafrost accelerates climate-warming-driven thaw and changes thaw patterns. Simulation analyses of groundwater flow and heat transport with freeze/thaw in typical cold-regions terrain with nested flow indicate that early thaw rate is particularly enhanced by flow, the time when adverse environmental impacts of climate-warming-induced permafrost loss may be severest. For the slowest climate-warming rate predicted by the Intergovernmental Panel on Climate Change (IPCC), once significant groundwater flow begins, thick permafrost layers can vanish in several hundred years, but survive over 1,000 years where flow is minimal. Large-scale thaw depends mostly on the balance of heat advection and conduction in the supra-permafrost zone. Surface-water bodies underlain by open taliks allow slow sub-permafrost flow, with lesser influence on regional thaw. Advection dominance over conduction depends on permeability and topography. Groundwater flow around permafrost and flow through permafrost impact thaw differently; the latter enhances early thaw rate. Air-temperature seasonality also increases early thaw. Hydrogeologic heterogeneity and topography strongly affect thaw rates/patterns. Permafrost controls the groundwater/surface-water-geomorphology system; hence, prediction and mitigation of impacts of thaw on ecology, chemical exports and infrastructure require improved hydrogeology/permafrost characterization and understanding.RésuméL’écoulement souterrain de l’eau dans les régions froides présentant un pergélisol accélère le dégel généré par le réchauffement climatique et change le modèle du dégel. Les simulations d’écoulement souterrain et de transport de chaleur avec gel/dégel dans les régions froides typiques et écoulement en réseau, indiquent que le taux de dégel précoce s’accroît particulièrement du fait de l’écoulement, à un moment où les impacts environnementaux défavorables d’une disparition du permafrost induite par le réchauffement climatique peuvent être les plus sévères. Pour le taux de réchauffement climatique le plus bas prévu par la Commission Intergouvernementale sur le Changement Climatique (IPCC), une fois qu’un écoulement souterrain significatif débute, les niveaux de pergélisol épais peuvent disparaître en plusieurs centaines d’années, mais survivre plus de 1000 ans quand l’écoulement est minimal. Le dégel à grande échelle dépend principalement du bilan d’advection de la chaleur et de la conduction dans la zone supra-pergélisol. Les masses d’eau à la base des taliks ouverts permettent un écoulement infra-pergélisol lent, avec une influence moindre sur le dégel régional. La prépondérance de l’advection sur la conduction dépend de la perméabilité et de la topographie. L’écoulement souterrain autour du pergélisol et l’écoulement à travers le pergélisol impactent le dégel différemment; le dernier type d’écoulement accroît le taux de dégel de façon précoce. La saisonnalité air-température augmente aussi le dégel précoce. L’hétérogénéité de l’hydrogéologie et la topographie affectent fortement caractéristiques et taux du dégel. Le pergélisol contrôle le système eau souterraine-eau de surface-géomorphologie ; par suite, la prévision et l’atténuation des impacts du dégel sur l’écologie, sur les mobilisations chimiques et sur le substrat nécessitent une caractérisation et une meilleure compréhension de l’hydrogéologie liée au pergélisol.ResumenEl flujo de agua subterránea en regiones frías que contienen un permafrost acelera el calentamiento climático impulsado por el descongelamiento y cambios en los patrones de descongelamiento. Los análisis de simulación del flujo de agua subterránea y del transporte de calor con congelamiento / descongelamiento en terrenos típicos de regiones frías con flujos jerarquizados indican que la tasa de deshielo temprana es particularmente realzada por el flujo y que la época en que los impactos ambientales adversos del calentamiento climático inducido por la pérdida de permafrost puede ser más severa. Para las tasas más lentas del calentamiento climático predichas por el Intergovernmental Panel on Climate Change (IPCC), una vez que un flujo significativo de agua subterránea comienza, las gruesas capas de permafrost pueden desaparecer en varios cientos de años, pero sobreviven más de 1000 años donde el flujo es mínimo. El descongelamiento a gran escala depende principalmente del balance de la advección y conducción de calor en la zona supra—permafrost. Los cuerpos de agua superficial sustentados por taliks abiertos permiten mostrar el lento flujo sub-permafrost, con una menor influencia en el descongelamiento regional. El dominio de la advección sobre la conducción depende de la permeabilidad y la topografía. El flujo de agua subterránea alrededor del permafrost y el flujo a través del permafrost impactan en forma diferente en el descongelamiento; este último aumenta la tasa de descongelamiento temprano. Estacionalmente la temperatura del aire también incrementa el deshielo temprano. La heterogeneidad hidrogeológica y la topografía afectan fuertemente las tasas / patrones de deshielo. El permafrost controla el sistema geomorfología—agua superficial—agua subterránea; por lo tanto la predicción y mitigación de los impactos del descongelamiento sobre la ecología, las exportaciones de productos químicos y la infraestructura requiere una mejor caracterización y entendimiento de la hidrogeología / permafrost.摘要具有永久冻土的寒区地下水流使气候变暖驱使的融化加速,并改变融化类型。具有嵌入水流的典型寒区地下水流及冻结/融化的热传导模拟分析表明早期消融速率主要由水流增强的,气候变暖导致的永久冻土消失引起的环境负效应的时间是严格的。根据联合国政府间气候变化专门委员会(IPCC)预计的最慢气候变暖速率,一旦明显的地下水流形成,厚的永久冻土层在几百年内会消失,但是在最小水流时可存在千年以上。大规模的消融更依赖于上永久冻土地带的热对流及传导平衡。下伏有开放融区的地表水体可以允许缓慢的地下永久冻土水流,这对区域消融影响较小。强于传导的对流优势取决于渗透性和地形。永久冻土附近的地下水流以及通过永久冻土的水流对消融的不同影响,后者增加早期消融速率。空气温度的季节性同样增强了早期消融。永久冻土控制地下水-地表水-地貌系统;所以消融对生态、化学输出以及基础设施的影响预测及减缓需要提高对水文地质/永久冻土的描述和理解。ResumoO fluxo de água subterrânea em regiões frias contendo permafrost acelera a fusão motivada por aquecimento climático e altera os padrões de fusão. A análise por simulação do escoamento de água subterrânea e de transporte de calor com congelamento/fusão em terrenos de regiões frias típicas com escoamento encaixado indicam que a taxa de fusão precoce é particularmente ampliada pelo fluxo, num momento em que os impactos ambientais adversos da perda de permafrost induzida pelo aquecimento climático podem ser mais severos. Para a mais baixa taxa de aquecimento climático prevista pelo Painel Intergovernamental sobre Mudanças Climáticas (IPCC), logo que se inicie um significativo fluxo subterrâneo, as camadas espessas de permafrost podem desaparecer em algumas centenas de anos, mas sobrevivem para cima de 1000 anos quando o fluxo é mínimo. A fusão em larga escala depende principalmente do balanço entre adveção e condução de calor na zona superior do permafrost. As massas de água superficial sobrepostas a taliks abertos permitem um fluxo lento na zona inferior do permafrost, com menor influência na fusão regional. O domínio da adveção sobre a condução depende da permeabilidade e da topografia. O fluxo de água subterrânea em torno do permafrost e o fluxo através do permafrost afetam a fusão de modo diverso; este último ampliando as taxas de fusão precoce. A heterogeneidade hidrogeológica e a topografia afetam fortemente as taxas/padrões de fusão. O permafrost controla o sistema geomorfológico-água subterrânea-água superficial; em consequência, a predição e a mitigação de impactos da fusão na ecologia, na exportação de químicos e nas infraestruturas requerem uma melhorada caracterização e compreensão da hidrogeologia/permafrost.

Hydrochemical evaluation of changing glacier meltwater contribution to stream discharge: Callejon de Huaylas, Peru / Evaluation hydrochimique de la contribution évolutive de la fonte glaciaire à l'écoulement fluvial: Callejon de Huaylas, Pérou

Abstract Discharge measurements, precipitation observations and hydrochemical samples from catchments of the Callejon de Huaylas watershed draining the Cordillera Blanca to the Rio Santa, Peru, facilitate estimating the glacier meltwater contribution to streamflow over different spatial scales using water balance and end-member mixing computations. A monthly water balance of the Yanamarey Glacier catchment shows elevated annual discharge over December 2001–July 2004 compared to 1998–1999, with net glacier mass loss in all months. Glacial melt now accounts for an estimated 58% of annual mean discharge, 23% greater than 1998–1999. At Lake Querococha, below Yanamarey (3.4% glacierized), a hydrochemical end-member mixing model estimates that 50% of the streamflow is derived from the glacier catchment. Average concentrations from the Rio Santa leaving the Callejon de Huaylas (8% glacierized) are modelled as a mixture with 66% deriving from glacierized tributaries of the Cordillera Blanca as opposed to the non-glacierized Cordillera Negra end member.

New permafrost is forming around shrinking Arctic lakes, but will it last?

Widespread lake shrinkage in cold regions has been linked to climate warming and permafrost thaw. Permafrost aggradation, however, has been observed within the margins of recently receded lakes, in seeming contradiction of climate warming. Here permafrost aggradation dynamics are examined at Twelvemile Lake, a retreating lake in interior Alaska. Observations reveal patches of recently formed permafrost within the dried lake margin, colocated with discrete bands of willow shrub. We test ecological succession, which alters shading, infiltration, and heat transport, as the driver of aggradation using numerical simulation of variably saturated groundwater flow and heat transport with phase change (i.e., freeze-thaw). Simulations support permafrost development under current climatic conditions, but only when net effects of vegetation on soil conditions are incorporated, thus pointing to the role of ecological succession. Furthermore, model results indicate that permafrost aggradation is transitory with further climate warming, as new permafrost thaws within seven decades.

A stochastic appraisal of the annual carbon budget of a large circumboreal peatland, Rapid River Watershed, northern Minnesota

The probable limits of the carbon budget of the Rapid River Watershed, within the greater Glacial Lake Agassiz Peatland in northern Minnesota, were evaluated using a Monte Carlo simulation approach. Carbon enters the peatlands in groundwater, precipitation, and primary productivity. Carbon leaves the peatlands by groundwater and surface water outflow and by the outgassing of methane. Results of the simulations of the carbon budget show that the peatland is now probably a sink for carbon, supported by field data showing peat is, in fact, accumulating at the rate of about 1 mm yr−1 [Glaser et al., 1997]. Excluding extreme values, Monte Carlo simulation results indicate that the Rapid River Peatland stores between −28.98 g C m−2 yr−1 (release) and 50.38 g C m−2 yr−1 (storage) with a mean accumulation of 12.74 g C m−2 yr−1 over the 1,506,200 m2 watershed. The peatland appears to be delicately poised with respect to net gain or loss of carbon.

Influence of vertical and lateral heat transfer on permafrost thaw, peatland landscape transition, and groundwater flow

Recent climate change has reduced the spatial extent and thickness of permafrost in many discontinuous permafrost regions. Rapid permafrost thaw is producing distinct landscape changes in the Taiga Plains of the Northwest Territories, Canada. As permafrost bodies underlying forested peat plateaus shrink, the landscape slowly transitions into unforested wetlands. The expansion of wetlands has enhanced the hydrologic connectivity of many watersheds via new surface and near-surface flow paths, and increased streamflow has been observed. Furthermore, the decrease in forested peat plateaus results in a net loss of boreal forest and associated ecosystems. This study investigates fundamental processes that contribute to permafrost thaw by comparing observed and simulated thaw development and landscape transition of a peat plateau-wetland complex in the Northwest Territories, Canada from 1970 to 2012. Measured climate data are first used to drive surface energy balance simulations for the wetland and peat plateau. Near-surface soil temperatures simulated in the surface energy balance model are then applied as the upper boundary condition to a three-dimensional model of subsurface water flow and coupled energy transport with freeze-thaw. Simulation results demonstrate that lateral heat transfer, which is not considered in many permafrost models, can influence permafrost thaw rates. Furthermore, the simulations indicate that landscape evolution arising from permafrost thaw acts as a positive feedback mechanism that increases the energy absorbed at the land surface and produces additional permafrost thaw. The modeling results also demonstrate that flow rates in local groundwater flow systems may be enhanced by the degradation of isolated permafrost bodies.

Migration Amidst Climate Rigidity Traps: Resource Politics and Social-Ecological Possibilism in Honduras and Peru

According to dominant narratives about adaptation to climate change, those facing worst-case scenarios, without means at their disposal to adapt in situ, face an ineluctable set of adaptation strategies that ultimately includes the permanent abandonment of geographic spaces rendered uninhabitable and unproductive for human use. Yet environmental stress and adaptive capacity are distributed unevenly, and power structures play a role in fashioning them. It is argued here that when access to land and water are impacted by environmental stress, the structures that mediate their access are reinforced, even as the adaptive alternatives for smallholders are undermined. In this way, dominant resource regimes set up migration as the primary viable alternative for adaptation among a dwindling set of choices. This framework is applied to two early analogues of climate change impacts: flooded Garífuna villages of Hondurass North Coast and communities enduring glacier recession and shifting hydrologic regimes in Perus Cordillera Blanca. In both cases, stress motivates new forms of migration that reinforce dominant power structures. In Honduras, migrants from wealthier social strata are moving on a more permanent basis, and in Peru, the once historical pattern of labor migration is becoming a practical necessity. These cases underscore the role of political economy in adaptation to climate change and adaptive migration in particular.

Using Diurnal Temperature Signals to Infer Vertical Groundwater-Surface Water Exchange

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan-view flux maps. Key advantages of heat tracing include cost-effective sensors and ease of data collection and interpretation, without the need for expensive and time-consuming laboratory analyses or induced tracers. While the collection of temperature data in saturated sediments is relatively straightforward, several factors influence the reliability of flux estimates that are based on time series analysis (diurnal signals) of recorded temperatures. Sensor resolution and deployment are particularly important in obtaining robust flux estimates in upwelling conditions. Also, processing temperature time series data involves a sequence of complex steps, including filtering temperature signals, selection of appropriate thermal parameters, and selection of the optimal analytical solution for modeling. This review provides a synthesis of heat tracing using diurnal temperature oscillations, including details on optimal sensor selection and deployment, data processing, model parameterization, and an overview of computing tools available. Recent advances in diurnal temperature methods also provide the opportunity to determine local saturated thermal diffusivity, which can improve the accuracy of fluid flux modeling and sensor spacing, which is related to streambed scour and deposition. These parameters can also be used to determine the reliability of flux estimates from the use of heat as a tracer.

Measuring glacier surface temperatures with ground-based thermal infrared imaging

Spatially distributed surface temperature is an important, yet difficult to observe, variable for physical glacier melt models. We utilize ground-based thermal infrared imagery to obtain spatially distributed surface temperature data for alpine glaciers. The infrared images are used to investigate thermal microscale processes at the glacier surface, such as the effect of surface cover type and the temperature gradient at the glacier margins on the glaciers temperature dynamics. Infrared images were collected at Cuchillacocha Glacier, Cordillera Blanca, Peru, on 23–25 June 2014. The infrared images were corrected based on ground truth points and local meteorological data. For the control points, the Pearsons correlation coefficient between infrared and station temperatures was 0.95. The ground-based infrared camera has the potential for greatly improving glacier energy budget studies, and our research shows that it is critical to properly correct the thermal images to produce robust, quantifiable data.