The Antarctic and Greenland ice sheets are experiencing significant mass change with heterogeneous spatial and temporal characteristics and global consequences such as sea level rise affecting millions of people in low-lying coastal areas. Advances in large-scale satellite remote-sensing, modeling, and machine learning have ushered a new era of improved monitoring and understanding of these changes. In this dissertation, we analyze the mass balance of glaciers across the ice sheets at basin and sub-basin scales using satellite gravimetric data from the Gravity Recovery and Climate Experiment (GRACE) mission using a novel regionally-optimized mascon methodology, as well as Mass Budget Method (MBM) estimates from grounding line discharge measurements and surface mass balance from regional climate models. We find that Totten and Moscow University glaciers in the marine sector of East Antarctica, with a total 5-meter sea level rise potential, have been losing mass at a rate of 18.5±6.6 Gt/yr from April 2002 to August 2016. The MBM estimate obtained with RACMO2.3p1 (Regional Atmospheric Climate Model version 2.3 part 1) is in excellent agreement with GRACE at a sub-basin scale, while those obtained with RACMO2.3p2 and MAR (Modèle Atmosphérique Régional) version 3.6.41 show less negative trends. These results are robust with respect to Glacial Isostatic Adjustment (GIA) uncertainty. By extending this methodology to the Amery Ice Shelf drainage basin in East Antarctica, we find this basin is in balance and is also in agreement with MBM/RACMO2.3p1 at a sub-basin scale, while MBM/RACMO2.3p2 and MBM/MAR3.6.41 produce more positive trends. The discrepancies shown by RACMO2.3p2 and MAR3.6.41 in these regions of East Antarctica are attributed to larger mean monthly SMB magnitudes. By adjusting all models to have the same mean magnitude as RACMO2.3p1, all MBM time-series fall into agreement with the independent gravimetric data. Furthermore, we implement the regional optimization approach in the Getz Ice Shelf drainage basin in West Antarctica, where previous studies have shown disagreements between GRACE and MBM estimates, and find that by minimizing leakage in the GRACE estimate, all MBM estimates are in excellent agreement with the gravimetric result. The Getz Ice Shelf basin is found to have a mass loss rate of 22.9±10.9 Gt/yr with an acceleration of 1.6±0.9 Gt/yr2 from April 2002 to November 2015 (the common time-period with the MBM estimates). We use an ensemble of 128,000 GIA forward models to ensure the results are robust with respect to GIA uncertainty. Lastly, we focus on improving the monitoring and understanding of glacier dynamics by implementing a deep Convolutional Neural Network (CNN) to automatically delineate glacier calving fronts from Landsat imagery on the Greenland Ice Sheet. By training the network on Jakobshavn, Sverdrup, and Kangerlussuaq glaciers and testing it on Helheim glacier, we demonstrate that the performance of the network is comparable to that of a human investigator, with a mean CNN error of 1.97 pixels (96.3 meters) compared to a mean human error of 1.89 pixels (92.5 meters) on the same resolution images. Thus, we show that CNNs enable large-scale monitoring of glacier dynamics across the globe, which offers new possibilities for an improved understanding of the processes affecting the mass balance of glaciers. Ultimately, a better understanding of the ice sheets is crucial for a better assessment of the effects of a changing cryosphere and sea level rise around the globe.

The World's Glaciers and Ice Caps (GIC) contain a sea level rise (SLR) equivalent of about 0.4 m. Although their potential sea level contribution is small compared to Greenland (7.4 m) or Antarctica (58.3 m), the GIC are the largest contributor to global SLR at present. During the last 20 years, the GIC contributed 2.5 cm SLR vs 1 cm for Greenland and Antarctica. Rising global sea levels and posing a significant problem to society.

Runoff from the melting GIC has an impact on the regional hydrology and freshwater supply. The latter is of great concern in highly populated regions such as Central Asia where it negatively affects economic activities and political stability.

Defining consistent methodologies to monitor the state of GIC in these regions and reduce uncertainties regarding their specific ice mass loss and relative contribution to SLR is critical not only to science but to the public, policy development, and implementation.

In this dissertation, we use available satellite and modeling techniques to estimate recent contribution to sea level rise by the ice-covered regions outside the two ice sheets during the last two decades.

We estimate glacier mass balance employing: time-variable gravity measurements by the NASA GRACE mission, and satellite altimetry by the NASA ICESat and the ESA CryoSat-2 mission. These techniques are applied in key regions of the Arctic, where increasing atmospheric and ocean temperatures have led to accelerating glacier mass losses.

In the second part of this work is focused on the glaciers High Mountains of Asia, the largest freshwater reservoir outside the Polar Regions. Here, we use a mixture of remote sensed observations and atmospheric models to characterize the effect of glacier mass loss on the water cycle of the Indus River Basin.

This work helps improve our general understanding of the mechanisms driving current glaciers and ice caps mass change and its relative impact on freshwater availability and sea level rise during the next century.