Glacial Flow, Sibinacocha

When a fierce, deep crack reverberates and all heads bob from ice to sky, unsure whether the tremor resulted from the cracking of ice or the sound of lightning, I feel again the glaring Beauty of this place. Beauty meaning not one or another pretty thing, but capital-B Beauty, that dynamic and therefore ephemeral quality we find in nature and in each other, all things subject to time. This landscape is ever dynamic, though its movements have shifted. It flows differently. 

From 17,500 meters above sea level, I write to you from a four-season tent pitched in precious soft ground and surrounded by the crystalline rocks of the Cordillera Vilcanota, the second most glaciated tropical mountain range in the world. To the Northwest is a trail I've walked many times. It leads to the base of Hatunrit'i, “Big Snow”, a peak aptly named, as it is enveloped in snow and ice such that I cannot discern its lithic figure. This is the fault of glaciers which have continuously carved out its hidden shape, all the while covering their tracks as more flakes fall on top; snow both drives the downward process and ensures an uninterrupted cycle of flow. Hatunrit'i and her two shorter sisters, peaks to the left and right, exhibit summit domes, the trick of glaciers, which still grace these peaks, the tallest in a pass which connects the east and the west, the Pacific and the Amazon. 

The lower peaks, back down the trail, and rising directly before my open tent door, are the tortured, jagged peaks I expect of a formerly glaciated landscape. The metamorphic mountains have been scooped out by glaciers; u-shaped valleys mark their path from peak to valley to the great Lago Sibinacocha below. Large hills of pulverized rock, plucked from the mountain, pushed down and out, line the trail of these glacial ghosts. The “moraines” are tell-tale signs of the size and timing of late ice flows.

It is easy to step into a landscape and imagine it timeless, or perhaps place it into the context of “deep time.” We imagine the geologic timescale so vast that we cannot perceive its motions, let alone affect its processes. But here in the Vilcanota, this notion is confronted by the awesome skyline of Hatunrit’i and the down-valley peaks, progressively deglaciating to stark, black forms, which lead to Sibinacocha, the largest alpine lake in the Andes, ever breaking its own record. They too were clothed, shrouded in ice like Hatunrit’i, but this century’s melting has unveiled evidence of violent carving and powerful flows once hidden from view.

As you, my reader, are bound to guess, based on the context of a changing global climate, Hatunrit’i will soon be unrobed, her wide gown removed, revealing the scars of glaciers that once carved her form.

The flows are shifting. Though precious ice remains, it no longer flows – melt water does instead. There is no longer enough snow added to Hatunrit’i’s peak to initiate the downward motion. Vilcanota’s glaciers, like almost every other glacier on Earth today, are receding (see graph). It is melting from the bottom up. The cracks I hear are not healthy sounds of flow, but telltale signs of a dying glacier.

For me, a budding geologist, I usually find myself in a state of awe at geologic power – the explosivity of a supervolcano, strength of an earthquake tearing rock apart, the heat and pressure that gives rise to hot springs. It seems dangerously hubristic to say that man’s industry has halted a geologic force that has shaped some of our most cherished landscapes including Yosemite, the Rocky Mountains, even New York City. But it has been demonstrated time and time again, and internationally recognized since 1995 (IPCC Second Assessment Report). The world’s scientists have agreed for 19 years that man’s influence is discernible in the climate record, and that our greenhouse gas emissions are causing an overall warming effect on the planet.

The flows have changed. Flowing ice is flowing water. A planet with a climate stable enough for the evolutionary success of the human species is shifting further and further away from the one to which we are adapted. The catalyst for change may be human, but the system’s response will not necessarily favor us. In fact, as the climate up here in the Peruvian Andes warms, three frog species have found a new habitat. As can be seen in the hundreds of millions of years of evolutionary record, climatic change selects some, and extincts others.

I am up here studying frogs. But I am also here to bear witness. I listen for her cracks. I cheer for snowfall. I climb inside her caves and caverns. And I still hold onto a (perhaps) naïve hope that my grandchildren will know the word “glacier” and visit a a mountain wrapped in white, with its ice flow in full force, and not to be left with a barren, scarred landscape – the evidence of our heedless march.

Figure 4.13 from IPCC Assessment Report 4, Working Group 1, 2007.

Large-scale regional mean length variations of glacier tongues (Oerlemans, 2005). The raw data are all constrained to pass through zero in 1950. The curves shown are smoothed with the Stineman (1980) method and approximate this. Glaciers are grouped into the following regional classes: SH (tropics, New Zealand, Patagonia), northwest North America (mainly Canadian Rockies), Atlantic (South Greenland, Iceland, Jan Mayen, Svalbard, Scandinavia), European Alps and Asia (Caucasus and central Asia).