Vanishing Ice Glaciers, Ice Sheets, and Rising Seas
Vivien Gornitz
PREFACE
W
hy should we care about vanishing ice and snow? Vanishing Ice: Glaciers, Ice Sheets, and Rising Seas vividly describes how the atmospheric accumulation of greenhouse gases generated by human activities has already begun to affect the Earth’s climate, most visibly near the poles and on high mountains. Arctic temperatures rise twice as fast as in the rest of the world. A once-perilous journey through the fearsome, ice-laden Northwest Passage has lately turned into a leisurely summer cruise through open waters for a growing number of large commercial and tour ships. The giant luxury cruise ship Crystal Serenity, carrying over 1,000 passengers with a crew of nearly 600, repeated its record-breaking 2016 voyage through the Northwest Passage the following summer, in August 2017. A sharp decline in Arctic summer sea ice since the 1980s is just one of the most conspicuous manifestations of the changing cryosphere—the world of ice—as our planet warms. Some scientists foresee nearly ice-free summers in the Arctic Ocean within the next several decades! On top of the Greenland Ice Sheet, warmer summers expand the area that thaws, even if only briefly, as occurred in mid-July of 2012, when nearly the entire surface of the Greenland Ice Sheet melted. In spite of the rarity of such widespread events (the previous such incident occurred in 1889), the extent and duration of summer melting has grown significantly in recent years. Arctic peoples notice changes in polar bear behavior and reindeer foraging habits. The stronger waves of a prolonged ice-free Arctic Ocean erode the shoreline, endangering scores of Native Alaskan fishing villages. The environmental changes impinge on the ability of indigenous Arctic
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populations to maintain traditional lifestyles. Sheila Watt-Cloutier, an Inuit spokeswoman, has emphasized how important snow and ice are to their traditional hunting culture. She declared: “We are in essence fighting for our right to be cold.� The effects of deicing the permafrost sweep across the Arctic. Trees tilt at crazy angles like drunken sailors, coastal cliffs crumble, wave-battered shorelines wash away, highways buckle, buildings sag and collapse, and lakes in the tundra appear and disappear as the changing climate transforms the regional ecology, hydrology, and landscape. Thawing permafrost and ground instability also affect Arctic construction, transportation, tourism, and development. However, a mixed picture emerges. Shipping will benefit from increasingly ice-free waters and considerably shortened transportation routes, cutting costs substantially. Development of potentially vast Arctic oil and mineral resources will open up many opportunities. At the same time, development of as-yet-untapped mineral wealth exposes fragile tundra and wildlife to new stresses from which recovery may be difficult. Ice tongues and shelves that ring much of Antarctica, as well as many high Arctic islands, and that hold ice sheets and maritime glaciers in check begin to thin and weaken. At least ten large, fringing ice shelves on the Antarctic Peninsula have crumbled one by one, like a pile of dominoes, since the 1990s. Tributary glaciers feeding the ice shelves have then accelerated seaward. On high mountain slopes around the world, most glaciers are also in retreat. Darkening peaks not only disappoint Alpine tourists, but also lead to more unreliable water supplies. Swollen spring river flows generate more flash floods. Also, as glaciers recede and alpine permafrost thaws, the high mountains become unglued, letting loose more rockfalls and avalanches. The visible changes may be just the tip of the proverbial iceberg. As permafrost thaws, will greenhouse gases like methane or carbon dioxide bubbling up from soggy, unfrozen Arctic soils and the seabed reinforce the ongoing warming trend? Which of these two greenhouse gases matters more to the permafrost climate feedback? Will Arctic vegetation grow wetter or drier? These questions grip scientists in a heated debate, as described in a later chapter.
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The ice-albedo feedback amplifies the unprecedented late twentieth– early twenty-first-century rise in Arctic temperatures and speeds up ice losses. Less summer sea ice means more open ocean water. An open, nearly ice-free broad expanse of open water reflects less sunlight, and instead absorbs more of the sun’s heat. As a result, more sea ice melts, which in turn allows additional escape of heat and moisture into the atmosphere. The associated feedbacks and their consequences make the Arctic a major crucible of climate change. But their reverberations echo far beyond the deep north, or other currently frozen realms. Changing Arctic landscapes and endangered lifestyles are not the only reasons why the vanishing cryosphere matters. What does the thawing cryosphere portend beyond polar regions and high mountain peaks? As succinctly stated in 2012 by former National Oceanic and Atmospheric Administration official Jane Lubchenko, “What happens in the Arctic doesn’t stay in the Arctic. What happens there often affects people around the world. Melting ice and glaciers in Greenland can contribute quite significantly to sea level rise, which affects people in coastal areas around the world.” Sea level rise represents the other side of the same coin of thawing ice sheets and glaciers. These two sides of the coin have been closely interwoven throughout most of geologic history, as initially outlined in Rising Seas: Past, Present, Future, and explored at greater length in Vanishing Ice: Glaciers, Ice Sheets, and Rising Seas. This close relationship continues today and will persist into the future. The worldwide menace of sea level rise looms over the tens of millions of people who live along the world’s shorelines and who face an evergrowing vulnerability to coastal storm floods, made worse by rising sea levels. Ice sheet losses, along with shrinking glaciers, already account for over half the observed rising sea level trend of roughly 3 millimeters (0.1 in) per year since 1993, and this share is likely to grow in the future. The vast stores of ice in Greenland and Antarctica would raise sea level by 66 meters (217 feet) if fully melted. The two still-frozen giants hold momentous keys to our future well-being. While a large-scale destabilization of the polar ice sheets appears quite unlikely within the next century or two, such a possibility cannot be ruled out entirely, nor can even greater degrees of melting be discounted still further into the future. Thus it
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becomes critical to gain a better understanding of the causes and effects of the receding world of ice—a major theme of this volume. Vanishing Ice describes the current state of the cryosphere, and offers plausible scenarios for how much and how fast ice may melt in the future, by what means, and with what consequences. The heavy rains, destructive winds, and high storm surges of three intense hurricanes in close succession that flooded much of southern Texas, devastated Caribbean islands, swept across the Florida Keys, and left most of Florida without power for days during August and September of 2017 starkly illustrate the present dangers faced by low-lying coastal areas. The vulnerability of the world’s shorelines to coastal storm floods will grow with rising sea levels. Many of the world’s most populous cities line the coast and face serious inundation risks: New York City, Los Angeles, London, Tokyo, Shanghai, Hong Kong, Mumbai (Bombay), Bangkok, and Miami, to name just a few. Some small island states, such as Tuvalu, Kiribati, and the Maldives, are already planning for eventual evacuation and relocation. The planet’s warm-up may bring us to a new climate regime that could ultimately endanger the cryosphere. We are inching toward a climate regime like that of past warm geological periods, such as that of the Last Interglacial, ~125,000 years ago, a time when sea level stood 6 meters (20 feet) or more higher, or even like the early to mid-Pliocene, 3.5–3 million years ago, which had atmospheric carbon dioxide levels similar to today’s (i.e., ~400 parts per million) but ~20 meters (66 feet) higher sea level. Climate experts warn against a temperature rise of more than 2°C (3.6°F), calling it a “dangerous anthropogenic interference with the climate system” (UNFCCC, 2010). But the long atmospheric lifetime of today’s increasing carbon dioxide emissions virtually ensures a warmer planet, a smaller cryosphere, and higher oceans. Vanishing Ice looks beyond sensational media coverage or dry technical literature to depict the dramatic changes rapidly transforming the cryosphere by illustrating the mounting evidence of the expanding meltdown. The facts, based on the latest scientific observations, build up a convincing case. Going beyond the findings of an earlier book (Rising Seas: Past, Present, Future), this volume meticulously probes the closely interconnected roles of mounting temperatures, a shrinking cryosphere,
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and higher oceans. This book aims not only to raise public awareness of the meteoric changes already transforming the cryosphere, but also to forcefully substantiate its vital role in planetary processes and in our future well-being. Thus the book highlights the widespread repercussions of ice loss, which will affect countless people far removed from frozen regions. Although Vanishing Ice avoids thorny policy issues or mitigation recommendations that are amply covered elsewhere, its straightforward, well-documented presentation opens the eyes of the reader to the serious environmental challenges ahead and enables him or her to make wellinformed choices that will help avert disaster. In addition to raising awareness, the book emphasizes that losing ice has global-scale consequences and therefore the big meltdown truly matters to all! A unique feature of the book is the long-term perspective gained by closely examining changes in the cryosphere and corresponding variations in sea level over the past few million years. The history of expansion and contraction of the Greenland and Antarctic ice sheets holds valuable clues to the future stability of these vast, icy storehouses. Added to geophysical and geochemical records of past climates are new observations and modeling studies probing the dynamic behavior of ice sheets, which will shed light on the critical questions of how much and how soon they will melt and what this means for future generations.
Gornitz
Praise for VANISHING
Vanishing Ice
ICE
“Vanishing Ice is an informative, engaging introduction to sea level rise and the total remake of the icy parts of our world already underway due novices and as informative to experts.”
V
MICHAEL OPPENHEIMER, ALBERT G. MILBANK PROFESSOR OF GEOSCIENCES
IVIEN GORNITZ is a geologist
AND INTERNATIONAL AFFAIRS, PRINCETON UNIVERSITY
and former special research scientist with the Columbia Univer-
sity Center for Climate Systems Research and the NASA Goddard Institute for Space Studies. Her books include Rising Seas: Past, Present, Future (Columbia, 2013).
“Anyone who wants a better understanding of the different parts of the cryosphere, the consequences of melting ice, and this aspect of climate change will find this book an invaluable resource.” SUZANNE B. O’CONNELL, PROFESSOR OF EARTH AND ENVIRONMENTAL SCIENCES, WESLEYAN UNIVERSITY
“Vanishing Ice brings readers to the cryosphere and its ongoing changes in a nuanced and informative fashion. Scientists as well as students and curious people alike will benefit from this fascinating book.” MARCO TEDESCO, LAMONT RESEARCH PROFESSOR, LAMONT-DOHERTY EARTH OBSERVATORY
Vanishing Ice
to climate change. Few books about scientific topics are as accessible to
Glaciers, Ice Sheets, and Rising Seas
T
HE ARCTIC is thawing. In summer, cruise ships sail through the once ice-clogged Northwest Pas-
sage, lakes form on top of the Greenland Ice Sheet, and polar bears swim farther and farther in search of waning ice floes. At the opposite end of the world, floating Antarctic ice shelves are shrinking. Mountain glaciers are in retreat worldwide, unleashing flash floods and avalanches. We are on thin ice—and with melting permafrost’s potential to let loose still more greenhouse gases, these changes may be just the beginning. Vanishing Ice is a powerful depiction of the dramatic transformation of the cryosphere—the world of ice and snow—and its consequences for the human world. Delving into the major components of the cryosphere, including ice sheets, valley glaciers, permafrost, and floating ice, Vivien Gornitz gives an up-to-date explanation of key current trends in the decline of ice mass. Drawing on a longterm perspective gained by examining changes in the cryosphere and corresponding variations in sea level over millions of years, she demonstrates the link between thawing ice and sea-level rise to point to the social and economic challenges on the horizon. Gornitz highlights the widespread repercussions of ice loss,
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which will affect countless people far removed from frozen regions, to explain
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Vivien Gornitz
why the big meltdown matters to us all. Written for all readers and students interested in the science of our changing climate, Vanishing Ice is an accessible and lucid warning of the coming thaw.