ALBERT

Description: In the Tropical Andes, a wide range of topographic and climatic settings results in a large diversity of glaciers distributed over mountain ranges and volcanoes. Previous studies, based on geodetic estimations, show that glaciers in this region have lost mass at a rate of -0.50 m w.e. yr〈sup〉-1〈/sup〉 during the last two decades. At the interannual time step, efforts to understand the mass balance variability as a direct response to the Andean climate, have been constrained by the number of available observations and a variety of interpolation approaches used to compute the glaciological mass balances. Thanks to the availability of point mass balance on seven tropical glaciers, we assess the annual signal of the surface mass balances during the 1990-2020 period. Thus, glaciers in the inner tropics are subjected to a less pronounced mass loss of -0.35 m w.e. yr〈sup〉-1〈/sup〉, while glaciers in the outer tropics exhibit a mass balance of -0.55 m w.e. yr〈sup〉-1〈/sup〉. Our results suggest that this contrasting behavior may be related to the latitudinal location and elevation of glaciers. The interannual cycles captured by the point mass balance correlate with climate variability and periodical patterns as El Niño Southern Oscillation. Although its behavior depends on the climatic conditions at the regional scale and the local topography, on the whole, glaciers are shrinking throughout the region with negative consequences in terms of water availability for Andean countries.

Description: The mass balance observations have been carried out on Chhota Shigri Glacier since 2002. Due to difficult glacier accessibility, dynamics, and involvement of different researchers, the measurement network differs in space over time. Further, almost all glaciological mass balance series are affected by the systematic biases due to specifically designed point mass balance network, and lack of basal and internal mass loss measurements. The goal of this study is to re-analyze the mass balances on Chhota Shigri Glacier and provide a homogenized series. We applied the nonlinear model of Vincent and others (2018) to capture the spatiotemporal changes in point mass balances and re-estimated the annual glacier-wide mass balances over 2002-2020. The nonlinear model also allows to detect the erroneous point measurements which are either corrected from the field notebooks or removed from the analysis. The mass balances are then homogenized applying the areal changes estimated using SPOT5 (2005) and Pléiades images (2014 and 2020), assuming a linear areal change. Finally, the mass balances are adjusted using the geodetic mass balances estimated by differencing ASTER and Pléiades DEMs (Oct 2003–Sept 2014) and Pléiades DEMs (Sept 2014–Sept 2020). The reanalyzed mean annual glacier-wide mass balance is estimated to be –0.47 ± 0.18 m w.e. a〈sup〉−1〈/sup〉 (equivalent to a cumulative mass loss of –8.40 m w.e.) with a standard deviation of 0.66 m w.e. a〈sup〉−1〈/sup〉 over 2002-2020. The glacier lost maximum mass of –1.29 ± 0.16 m w.e. in 2017/18 while gained a mass of 0.49 ± 0.19 m w.e. in 2004/05.

Description: Precipitation in the tropics is dominated by variability on seasonal, intraseasonal and diurnal scales. However, at the finest spatial scales, this variability can be strongly modulated by numerous local factors that represent a range of physical processes. One aspect of this modulation that operates across multiple scales is the orientation of coastal and inland topography relative to the background wind. This is particularly relevant where complex topography occurs in the vicinity of tropical coastlines, which can cause local changes in moisture flux convergence. Another aspect is the coupling of the diurnal cycle to changes in surface heating, surface moisture, column moisture, background wind and cloudiness. This link between clouds, radiation and diurnally forced convection forges a two-way interaction between the intraseasonal scales and mesoscale variability. Further to these modulating factors, propagating disturbances from neighbouring coastlines, and interactions between coastal processes across adjacent seas introduces a non-local mesoscale source of variability, particularly amidst the complex archipelago of the Maritime Continent. These processes also occur outside the deep tropics, where the added complexity of mid-latitude interactions contributes to the overall variation in precipitation. Multiple spatial and temporal scales are impacted by these competing sources of variability, which presents a challenge in quantifying their representation and impact in weather and climate models. This has implications for weather prediction and down-scaling of climate change projections. This talk will examine some of the local manifestations of scale-interactions in tropical Queensland (Australia) and the Maritime Continent, using diverse observational datasets and high-resolution numerical modelling.