My visit to Perito Moreno Glacier, one of the few glaciers in the world known to be advancing rather than in retreat, coincided with a rainstorm, which provided dramatic cloud cover over the mountains behind the glacier and prevented the sun from creating impossible contrasts of highlight and shadow. So it was a blessing to get that storm rolling in at the same time I arrived. Indeed, the frozen tsunami of ice was a deeper blue thanks to the shade provided by the storm clouds overhead in Los Glaciares National Park, Patagonia, Argentina.