Deforestation Impacts on Amazon-Andes Hydroclimatic Connectivity

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.

DInSAR monitoring of glacier dynamics in Cordillera Blanca and Vilcabamba

<p>The effects of climate change are causing atypical changes dynamics of tropical glaciers. Conventional methods and optical images were ineffective in measuring these changes periodically due to the complexity of remote mountainous regions and cloud cover. In this research, a Differential Interferometric Synthetic Aperture Radar (DInSAR) analysis has gone performed with Sentinel-1 data from February 2019 to March 2020 in the Cordillera Blanca and Vilcabamba for Mapping displacement and subsidence. The measurements were compared with surface temperature and precipitation, providing zonal statistics to identify and assess regions associated with Glacial Lake Outburst Floods (GLOFs) hazards and enhanced understanding of the glacier dynamics in response to changing climatic conditions.</p>

Similar Holocene glaciation histories in tropical South America and Africa

Tropical glaciers have retreated alongside warming temperatures over the past century, yet the way in which these trends fit into a long-term geological context is largely unclear. Here, we present reconstructions of Holocene glacier extents relative to today from the Quelccaya ice cap (Peru) and the Rwenzori Mountains (Uganda) based on measurements of in situ14C and 10Be from recently exposed bedrock. Ice-extent histories are similar at both sites and suggest that ice was generally smaller than today during the first half of the Holocene and larger than today for most, if not all, of the past several millennia. The similar glaciation history in South America and Africa suggests that large-scale warming followed by cooling of the tropics during the late Holocene primarily drove ice extent, rather than regional changes in precipitation. Our results also imply that recent tropical ice retreat is anomalous in a multimillennial context.

Holocene glaciation in the Rwenzori Mountains, Uganda

Tropical glaciers are retreating rapidly, threatening alpine ecosystems across the low latitudes. Understanding how tropical glaciers responded to past periods of warming is crucial for predicting and adapting to future climate change, yet relatively little is known about glacial fluctuations in tropical regions during the recent past (i.e., the Holocene Epoch). This is particularly true in the African tropics, where data constraining the timing and magnitude of Holocene glacial fluctuations in the region are sparse and where temperatures during the middle Holocene were perhaps as warm as or warmer than today. Here we present new beryllium-10 surface-exposure ages that constrain Holocene glacial extents in the equatorial Rwenzori Mountains, Uganda. These results document rapid Early Holocene (~11.7–8.2 ka) glacial retreat in two separate catchments and indicate that Late Holocene (~4.2 ka-present) deposits mark the greatest expansion of Rwenzori glaciers during the last ~11 ka. Holocene glacial fluctuations elsewhere in tropical Africa and in tropical South America are broadly similar to those in the Rwenzori, with most tropical glaciers retreating rapidly during the Early Holocene and remaining near or inboard of their Late Holocene positions through much of Holocene time. The similarity of Holocene glacial fluctuations across the tropics implies that low-latitude glaciers responded to a common forcing mechanism, most likely temperature. Although the drivers of Holocene temperature changes in the tropics remains enigmatic, these data help constrain the expression of tropical temperature changes in the low latitudes.

Variation of glacial dynamics in Peru: from valley glaciers to mountain glaciers in a context of climate change

<p>One of the effects of climate change on tropical glaciers is the accelerated reduction of their glacial tongue, reflected in a morphometric variation. Many glaciers that had pronounced tongues and that extended through a valley (Valley glacier) now have reduced their fronts located in the upper parts of the valleys (Mountain glacier).</p><p>This has been studied with glaciers of Peru located in 18 mountain ranges located from S 8°20'56" to 15°53'26" and W 77°56'10" to 69°05'14", which are an important solid water reserve that directly supplies the population of 11 departments.</p><p>The study focused on the "digit 1" (primary classification) of the Global Land Ice Measurement from Space (GLIMS), which classifies the glaciers mainly in: valley glaciers and mountain glaciers. The processing of raster and vector data through the use of geographic information system and remote sensing tools allowed to analyze the changes and variations affecting glaciers with respect to their morphometry. For this, a comparison was made between glacier coverage in 2016 (using images Sentinel 2), produced by INAIGEM, and the baseline of the glacier coverage of 1955 and 1970 (using aerial photography), from the first inventory of glaciers in Peru, produced by Hidrandina S.A.</p><p>The results show a significant morphometric variation of 83.7%, where valley glaciers (from Hidrandina inventory) became mainly mountain glaciers. Nowadays only four mountain ranges have mountain glaciers inside whereas in the past it were nine. When we analyze the results for watersheds, the most morphometric changes were 89% in the Atlantic watershed, followed by 57% in the Pacific watershed; in the Amazon watershed there was not any registration of any mountain glaciers since the first inventory in Peru. The surface changes do not show specific any predominant aspect, and average slopes are between 25° and 50°.</p><p>The glacial tongues that are considered valley glacier area located in ablation zones, where the mass balance is negative and there is more susceptibility to reducing their mass and, consequently, to variations in shape and size in a short period. This change has been accentuated in recent decades.</p>

Distribution and morpho-thermal characteristics of rock glaciers in southern Peru: case, Cordilleras Huanzo and Chila

<p>Climate change generates significant impacts on high mountain regions, especially considering the sensitivity of tropical glaciers. However, information about rock glaciers are very scarce and there is very limited research in this field in Peru. Rock glacier concentrate mainly in the southern part of Peru where 95% of rock glaciers are located. Here we present for the first time an overview of rock glacier occurrence and characteristics in Peru.</p><p>The Cordilleras Huanzo and Chila are located in the mountain ranges in the southern region of Peru, Huanzo in the administrative region of Apurimac, Arequipa, Cusco and Ayacucho, while Chila in Arequipa. Both cordilleras extend from S 15°39'41.36" to 14°03'17.54" and W 73°24'12.55" to 71°27'113.20". For this study, remote sensing tools and geographic information system were applied, using images from Google Earth-Pro and SASPlanet, corrected DEM ALOS Palsar (12.5m), MERIT DEM (90m) and WorldClim data (1970-2000) 1 km<sup>2</sup>.</p><p>The results indicate that in the cordillera Huanzo there are 317 rock glaciers with a total area of 26.97 km<sup>2</sup> and in the cordillera Chila there are 289 rock glaciers with 17.96 km<sup>2</sup>. Concerning their activity or dynamic there are 295 intact (active and inactive) rock glaciers and 311 relict or fossil rock glaciers.</p><p>The results further indicate that rock glaciers are located in thermal ranges between -1.53°C and 3.97°C. The relict or fossil types are located in the thermal range between -1.34°C and 3.97°C, while intact types between -1.53°C and 2.56°C. The rock glaciers of the cordillera Huanzo are located at an average altitude of 4497 to 5221 m.a.s.l., while in the cordillera Chila at 4470 to 5454 m.a.s.l. The aspect is predominantly S to SW.</p><p>Rock glaciers contain ice which may represent a potential water reserve in arid regions in Southern of Peru. The greatest distribution of these resources is found in the Camana and Ocoña basins of the Pacific watershed with 38.1 km<sup>2</sup> of rock glacier area. In the Atlantic watershed, 6.8 km<sup>2</sup> of rock glaciers are located in the Alto Apurimac and Ocoña basins.</p>

Vulnerability of C stocks in Polylepis forests of the Peruvian Andes under climate change – evidence from laboratory incubations, microbial nutrient constraints and enzyme activities

<p>Soils are the largest stock of terrestrial carbon, the dynamics of soil organic C (SOC) are controlled by microbial physiology, but how it promotes stable SOC and how it would change with warming, remains unknown. The Huascarán National Park (HNP), the largest mass of tropical glaciers in the world, has lost 20-30% of its glacial cover and the temperatures in this biosphere have risen 0.1°C per decade since 1970. However, no information on the HNP soil carbon stocks is available. As managing SOC is important for global warming mitigation, we study the soil C stocks in Polylepis forests of three valleys in the HNP along a temperature gradient relative to elevation (3300 to 4500 m asl), and their vulnerability to decomposition with increasing temperatures and combined labile C and nutrient (N+P) additions.</p><p>We found that higher altitude soils have higher C:N:P ratios which indicates that, as expected, soils at high altitudes are nutrient limited. Also, the activities of the N acquiring enzymes: NAGase and leucine-aminopeptidase, C acquiring enzymes: beta-glucosidase, cellobiosidase, beta-xylosidase and phosphatase were positively correlated with altitude, which indicate that N and P availability decreased with altitude across our gradient. This could make high altitude soils vulnerable to C losses, not just due to increased temperatures, but also due to increased rhizosphere priming effects. Climate warming might increase plant growth and belowground C allocation, which in turn could lead to priming due to nutrient mining.</p><p>We found no differences across altitudes in microbial biomass (Cmic) measured with the chloroform fumigation extraction method. We are currently analysing microbial community composition (by PLFA’s and DNA based methods). We will present data on microbial CUE of glucose decomposition, and how it is related to soil C/N ratios, nutrient availability and nutrient requirements, and community composition of the microbes. We also aim to test whether higher CUE is related to higher C stabilisation potential in the form of microbial necromass residues (amino sugars), or higher C loss when microbes efficiently growing on labile substrates will also increase the decomposition of more stable SOC (priming).</p>