NOTES
1. WHITHER THE SNOWS OF YESTERYEAR?
    1.  Barry and Gan (2011), p. 167; Intergovernmental Panel on Climate Change (2013a), table 4.1.
    2.  Barry and Gan (2011), p. 3.
    3.  Oxygen and hydrogen atoms in ordinary ice form tetrahedral bonds 109.5° apart. Stacking tetrahedra into a three-dimensional lattice creates a crystal with overall hexagonal symmetry (as in a snowflake). Ice can exist in at least 15 distinct phases, each with a different crystal structure, over a broad range of very low temperatures and high pressures.
    4.  “Eskimo,” once applied to all indigenous Arctic peoples of eastern Siberia, Alaska, Canada, and Greenland, now refers more narrowly to the Iñupiaq and Yupik people of Alaska, while those in Arctic Canada and Greenland are collectively called “Inuit.” The timing of the early migration based on genetics is discussed in Achilli et al. (2013).
    5.  Ingstad and Ingstad (2001).
    6.  Wikipedia, “Northwest Passage,” https://en.wikipedia.org/wiki/Northwest_Passage (last modified October 6, 2018).
    7.  “Lost Franklin Expedition Ship Found in the Arctic,” CBC News, September 9, 2014, https://www.cbc.ca/news/politics/franklin-expedition-ship-found-in-the-arctic-1.2760311; “Franklin Expedition Ship Found in Arctic ID’d as HMS Erebus,” CBC News, October 1, 2014, https://www.cbc.ca/news/politics/franklin-expedition-ship-found-in-arctic-id-d-as-hms-erebus-1.2784268.
    8.  Paul Watson, “Ship Found in Arctic 168 Years After Doomed Northwest Passage Attempt,” Guardian, September 12, 2016, http://www.theguardian.com/world/2016/sep/12/hms-terror-wreck-found-arctic-nearly-170-years-northwest-passage-attempt/; Government of Canada, “Parks Canada Media Statement—Validation of Discovery of HMS Terror” (accessed January 1, 2017).
    9.  Henderson (2009).
  10.  The North Polar Regions: A Geographical and Navigational Study, “Appendix D, Chronology of North Polar Exploration,” http://norpolar.tripod.com/chron.html (accessed July 10, 2013).
  11.  Piri Reis, an Ottoman admiral and cartographer, compiled a world map in 1513 from various sources. This map, according to some, purportedly shows the coastline of Antarctica as it would appear without ice. This knowledge supposedly came from advanced ancient sources. However, when centered at 0° latitude, 0° longitude on an azimuthal equidistant projection, the map outlines the coastlines of France, Spain, West Africa, and South America down to southern Brazil fairly well, but deviates sharply beyond Uruguay, showing a coastline with little resemblance to Antarctica’s. See Steven Dutch, “The Piri Reis Map,” http://web.archive.org/web/20171226235246/https://www.uwgb.edu/dutchs/PSEUDOSC/PiriRies.HTM.
  12.  Two others, a British naval captain, Edward Branfield, and an American sealer, Nathaniel Palmer, also sighted Antarctica within days of Bellingshausen.
  13.  Quoted in Walker (2013), p. 144.
  14.  Wikipedia, “Comparison of the Amundsen and Scott Expeditions,” http://en.wikipedia.org/wiki/Comparison_of_the_Amundsen_and_Scott_Expeditions (last modified September 3, 2018).
  15.  Although best known for the voyage of the Endurance, Shackleton previously participated in the National Antarctic (Discovery) Expedition (1901–1903) and led the Nimrod Expedition (1907–1909) in which he and his party set a new southern record at 88°23′S, 162°E (only 180 kilometers [118 miles] from the South Pole) in January of 1909. His final expedition to Antarctica ended in South Georgia with his death in 1922.
  16.  Summerhayes (2008).
  17.  National Research Council (2012).
  18.  Goddard Institute for Space Studies, National Aeronautics and Space Administration (NASA), “Long-Term Warming Trend Continued in 2017: NASA, NOAA,” January 18, 2016, https://www.giss.nasa.gov/research/news/20180118/ (accessed January 19, 2018).
  19.  Arctic Monitoring and Assessment Programme (2017); “Surface Air Temperature,” in Arctic Report Card 2017, ed. J. Richter-Menge, J. E. Overland, J. T. Mathis, and E. Osborne, pp. 5–12 (NOAA, 2017), ftp://ftp.oar.noaa.gov/arctic/documents/ArcticReportCard _full_report2017.pdf (accessed February 12, 2018).
  20.  Arctic Monitoring and Assessment Programme (2017).
  21.  Comiso (2012); Stroeve et al. (2012).
  22.  Defined as ocean with an ice concentration of 15 percent or more.
  23.  Arctic Monitoring and Assessment Programme (2017).
  24.  National Snow & Ice Data Center, “Arctic Sea Ice 2017: Tapping the Brakes in September,” October 5, 2017, http://nsidc.org/arcticseaicenews/2017/10/arctic-sea-ice-2017-tapping-the-brakes-in-september/ (accessed October 6, 2017).
  25.  National Snow & Ice Data Center, “Arctic Sea Ice Maximum at Second Lowest Level in the Satellite Record,” March 23, 2018, http://nsidc.org/arcticseaicenews/2018/03/arctic-sea-ice-maximum-second-lowest/ (accessed April 24, 2018).
  26.  National Snow & Ice Data Center, “Freezing in the Dark,” November 2, 2017, http://nsidc.org/arcticseaicenews/2017/11/ (accessed February 13, 2018); Andrea Thompson, “Sea Ice Hits Record Lows at Both Poles,” February 13, 2017, https://www.scientificamerican.com/article/sea-ice-hits-record-lows-at-both-poles/ (accessed February 17, 2017).
  27.  Waldman (2017).
  28.  Overduin and Solomon (2011).
  29.  The Little Ice Age lasted roughly from the thirteenth century to the mid-nineteenth century.
  30.  Revkin (2008).
  31.  Van den Broecke et al. (2016); Forsberg et al. (2017); Harig and Simons (2015).
  32.  The Greenland and Antarctic ice sheets together would raise sea level by 66 meters, if both melted entirely (see table 1.1).
  33.  Straneo and Heimbach (2013); Joughin et al. (2012).
  34.  Joughin et al. (2014); Rignot et al. (2014).
  35.  Stroeve et al. (2012).
  36.  Viñas (2012).
  37.  Tedesco et al. (2016).
  38.  Quinn (2007). The Arctic haze introduces conflicting feedbacks. Although sulfate aerosols scatter sunlight, cooling the surface, black carbon or soot weakly absorbs solar energy. Black carbon or soot disproportionately affects regional climate by creating a haze that spreads over highly reflecting Arctic snow and ice. Sulfate aerosols help increase the number of cloud droplets, whitening clouds and making them more reflecting (cooling effect). However, smaller droplets induce more downwelling infrared emission and, hence, warming.
  39.  Hadley and Kirchstetter (2012).
  40.  Alley (2007).
  41.  The Atlantic Meridional Overturning Circulation (AMOC) includes winds and tides, in addition to salinity- and temperature-driven ocean currents (see also Broecker, 2010).
  42.  Hu et al. (2011); Yin et al. (2010).
  43.  Intergovernmental Panel on Climate Change (2013a); Intergovernmental Panel on Climate Change (2013b).
  44.  Earth System Research Laboratory, National Oceanic and Atmospheric Administration, “Trends in Atmospheric Carbon Dioxide,” https://www.esrl.noaa.gov/gmd/ccgg/trends/ (accessed February 14, 2018); CO2.Earth, “Annual CO2 Data,” http://www.co2.earth/annual-co2/ (accessed June 29, 2018). The upward curve is punctuated by a rhythmic seasonal rise and fall, due largely to Northern Hemisphere vegetation. Photosynthesis consumes carbon dioxide during northern spring and summer; it is released during winter, as the vegetation becomes dormant
  45.  Intergovernmental Panel on Climate Change (2013a); Intergovernmental Panel on Climate Change (2013b).
  46.  Greenhouses also retain heat because they protect from the wind and reduce heat losses by conduction and convection.
  47.  United Nations Environment Programme (2007).
  48.  Navab (2011).
  49.  Bradley et al. (2006).
  50.  Bolch (2017); Pritchard (2017).
  51.  Belmecheri et al. (2015).
  52.  Huggel et al. (2012).
  53.  Horstmann (2004).
  54.  National Oceanic and Atmospheric Administration, “NOAA: 2017 Was 3rd Warmest Year on Record for the Globe,” January 18, 2018, https://www.noaa.gov/news/noaa-2017-was-3rd-warmest-year-on-record-for-globe (accessed January 19, 2018); Goddard Institute for Space Studies, NASA, “Long-Term Warming Trend Continued in 2017.”
  55.  Sea Level Change, NASA, “Key Indicators: Global Mean Sea Level,” https://sealevel.nasa.gov/understanding-sea-level/key-indicators/global-mean-sea-level (Sea level rise plot covers January 1993 to October 9, 2017); AVISO+, “Mean Sea Level Rise (January 5, 1993 to November 17, 2017),” https://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level.html (posted March 26, 2018).
  56.  Gornitz (2013).
  57.  Dieng et al. (2017); Rietbroek et al. (2016).
  58.  Intergovernmental Panel on Climate Change (2013a); Intergovernmental Panel on Climate Change (2013b). See also appendix A.
  59.  Neumann (2015). The 1-in-100-year flood is one with a 1 percent chance of occurring in any given year.
  60.  Hauer et al. (2016).
  61.  Glacial isostatic rebound (see glossary); McGuire (2012).
  62.  Gautier et al. (2009).
  63.  Teck, “United States Operations: Red Dog Operations,” https://www.teck.com/operations/united-states/operations/red-dog/.
  64.  United Nations Framework Convention on Climate Change (2010).
  65.  Miller et al. (2012).
2. ICE AFLOAT—ICE SHELVES, ICEBERGS, AND SEA ICE
    1.  Rignot et al. (2013).
    2.  Barry and Gan (2011), pp. 278–279.
    3.  National Snow & Ice Data Center, “Larsen B Ice Shelf Collapses in Antarctica,” March 18, 2002, http://nsidc.org/news/press/larsen_B/2002.html (updated March 21, 2002). The ice slab was 220 meters (720 feet) thick and ~3,250 square kilometers (1,255 square miles) in area.
    4.  Rignot et al. (2004); Scambos et al. (2004).
    5.  Khazendar et al. (2015).
    6.  NASA press release, May 14, 2015. “Study Shows Antarctica’s Larsen B Ice Shelf Nearing Its Final Act.” https://www.nasa.gov/press-release/nasa-study-shows-antarctica-s-larsen-b-ice-shelf-nearing-its-final-act/
    7.  Rebesco et al. (2014).
    8.  Holland et al. (2015).
    9.  Hogg and Gudmundsson (2017); Viñas (2017).
  10.  NASA Earth Observatory, WorldView-2 satellite image, March 23, 2013, http://earthobservatory.nasa.gov/IOTD/view.php?id=81174.
  11.  Pelto (2015).
  12.  Paolo et al. (2015). See also chap. 6, “Ice Shelves in Trouble.”
  13.  Quoted in Fox (2012).
  14.  Ilulissat, in Greenlandic; An et al. (2017).
  15.  David Bresson, “The Science Behind the Iceberg That Sank the Titanic,” Scientific American, April 14, 2012, https://blogs.scientificamerican.com/history-of-geology/the-science-behind-the-iceberg-that-sank-titanic/; BBC History, “The Iceberg That Sank Titanic—Origins of the Titanic Iceberg,” http://www.bbc.co.uk/history/topics/iceberg_sank_titanic.
  16.  Joughin et al. (2014).
  17.  Chelsea Harvey, “One of the World’s Fastest Melting Glaciers May Have Just Lost Its Biggest Chunk of Ice on Record,” The Washington Post, August 19, 2015, https://www.washingtonpost.com/news/energy-environment/wp/2015/08/19/one-of-the-worlds-fastest-melting-glaciers-may-have-just-lost-its-biggest-chunk-of-ice-ever/?utm_term=.4afdc3c25606 (accessed October 5, 2017).
  18.  McGrath et al. (2013).
  19.  Steig (2016); Bromwich et al. (2014).
  20.  Cook and Vaughan (2010).
  21.  Fox (2012). Note that the −9°C refers to the average annual temperature threshold, whereas the 0°C refers to the average summer temperature line.
  22.  Davies (2017); Fox (2012); Qiu (2013); Scambos et al. (2004).
  23.  MacGregor et al. (2012).
  24.  Alley et al. (2015); Schmidtko et al. (2014).
  25.  Paolo et al. (2015).
  26.  Depoorter et al. (2013); Rignot et al. (2013).
  27.  Rignot et al. (2004); Scambos et al. (2004).
  28.  Shepherd et al. (2012).
  29.  Favier et al. (2014).
  30.  Mercer (1978); Joughin and Alley (2011); Joughin et al. (2012).
  31.  Straneo and Heimbach (2013); Joughin et al. (2012).
  32.  Joughin et al. (2012); Joughin et al. (2014).
  33.  An et al. (2017).
  34.  Matilsky and Duwadi (2008).
  35.  Matilsky and Duwadi (2008).
  36.  Wadhams (2013).
  37.  Bruneau (2004); United States Coast Guard, International Ice Patrol (IIP), “About International Ice Patrol (IIP),” http://www.navcen.uscg.gov/?pageName=IIPHome; Canadian Coast Guard, Ice Navigation in Canadian Waters, Chapter 3, “Ice Climatology and Environmental Conditions,” http://www.ccg-gcc.gc.ca/folios/00913/docs/icenav-ch3-eng.pdf.
  38.  Marko et al. (2014).
  39.  United States Coast Guard Navigation Center, https://www.navcen.uscg.gov/?page?Name=IIPHome. (Last updated September 25, 2018).
  40.  Barry and Gan (2011), p. 291.
  41.  Barry and Gan (2011), p. 293; Diemand (2001/2008), p. 1262.
  42.  Wadhams (2013); Barry and Gan (2011), p. 293.
  43.  Diemand (2001/2008), p. 1262.
  44.  Very large icebergs may extend into subzero water at depth, due to the lowering of the freezing point with salinity.
  45.  Diemand (2001/2008), p. 1261.
  46.  National Snow & Ice Data Center, “2016 Ties with 2007 for Second Lowest Arctic Sea Ice Minimum,” September 15, 2016, http://nsidc.org/arcticseaicenews/2016/09/2016-ties-with-2007-for-second-lowest-arctic-sea-ice-minimum/ (accessed September 16, 2016).
  47.  Barry and Gan (2011), p. 237.
  48.  Serreze and Stroeve (2015).
  49.  Pistone et al. (2014).
  50.  Arctic Monitoring and Assessment Programme (2017).
  51.  National Snow & Ice Data Center, “Arctic Sea Ice 2017: Tapping the Brakes in September,” October 5, 2017, http://nsidc.org/arcticseaicenews/2017/10/arctic-sea-ice-2017-tapping-the-brakes-in-september/ (accessed October 6, 2017).
  52.  Arctic Monitoring and Assessment Programme (2017); Stroeve et al. (2014).
  53.  National Snow & Ice Data Center, “Arctic Sea Ice Maximum at Record Low for Third Straight Year,” March 22, 2017, https://nsidc.org/news/newsroom/arctic-sea-ice-maximum-record-low-third-straight-year/ (accessed May 25, 2017).
  54.  National Snow & Ice Data Center, “2018 Winter Arctic Sea Ice: Bering Down,” April 4, 2018, http://nsidc.org/arcticseaicenews/2018/04/2018-winter-arctic-sea-ice-bering-down/ (accessed April 24, 2018); National Snow & Ice Data Center, “Arctic Sea Ice Maximum at Second Lowest in the Satellite Record,” March 23, 2018, https://nsidc.org/news/newsroom/arctic-sea-ice-maximum-second-lowest-satellite-record (accessed April 24, 2018). The Arctic winter sea ice maximum extent was 14.5 million square kilometers (5.6 million square miles) on March 17, 2018, as compared with the record lowest maximum of 14.4 square kilometers (5.6 million square miles) set on March 7, 2017.
  55.  Serreze and Stroeve (2015).
  56.  Perovich et al. (2016).
  57.  Arctic Monitoring and Assessment Programme (2017).
  58.  Perovich et al. (2014).
  59.  Stroeve et al. (2014).
  60.  Pithan and Mauritsen (2014).
  61.  Stroeve et al. (2014).
  62.  Serreze and Stroeve (2015).
  63.  Swart (2017).
  64.  Arctic Monitoring and Assessment Programme (2017); Overland and Wang (2013).
  65.  Masters (2014).
  66.  Cohen et al. (2014); Masters (2014); Francis and Vavrus (2012).
  67.  Screen and Simmonds (2014); Cohen et al. (2014).
  68.  Screen (2017).
  69.  Bintanja et al. (2013).
  70.  Depoorter et al. (2013); Rignot (2013); Pritchard et al. (2012).
  71.  Holland and Kwok (2012).
  72.  National Snow & Ice Data Center, “Antarctic Maximum Extent,” in “Arctic Sea Ice 2017: Tapping the Brakes in September” (accessed October 6, 2017); “Arctic Sea Ice Maximum at Second Lowest in the Satellite Record” https://nsidc.org/news/newsroom/arctic-sea-ice-maximum-second-lowest-satellite-record (accessed April 24, 2018).
3. IMPERMANENT PERMAFROST
    1.  Péwé (2014).
    2.  Kramer (2008); Larmer (2013).
    3.  Barry and Gan (2011), p. 167; Osterkamp and Burn (2002).
    4.  Péwé (2014).
    5.  Péwé (2014); see glossary.
    6.  Global Terrestrial Network for Permafrost (GTN-P), https://gtnp.arcticportal.org/ (accessed October 10, 2017); Romanovsky et al. (2010). Ground temperatures are measured at the depth of zero annual amplitude.
    7.  Lachenbruch and Marshall (1986).
    8.  Exploratorium, Ice Stories, “Tundra and Permafrost,” http://icestories.exploratorium.edu/dispatches/big-ideas/tundra-and-permafrost.
    9.  The reason why water, unlike most liquids, expands upon freezing is explained in chapter 1.
  10.  As in congelation sea ice (see chap. 2), ice grows vertically with its c-axis oriented horizontally (Corte [1969]). Maximum growth occurs in the downward direction perpendicular to c (i.e., along the a-axis).
  11.  For a fuller discussion on ice lens formation and frost heaving, see, e.g., Davis (2001), pp. 67–95, and Rempel (2010).
  12.  Davis (2001), p. 110.
  13.  Geologists call this type of igneous intrusion a laccolith.
  14.  Davis (2001), pp. 121–131.
  15.  Karst topography, a landscape in limestone or dolomite riddled by subsurface caves, disappearing streams, sinkholes, and underground drainage, was named after a region between Slovenia and Italy.
  16.  Grosse et al. (2013), section 8.21.3.
  17.  Grosse et al. (2013), section 8.21.6. Oriented lakes may also form by alignment along faults or joints in rocks, or along contacts between different rock or soil types.
  18.  U.S. Army Corps of Engineers, Engineer Research and Development Center, “Permafrost Tunnel Research Facility,” https://www.erdc.usace.army.mil/CRREL/Permafrost-Tunnel-Research-Facility/.
  19.  Quoted in Walker (2007).
  20.  Rosen, “Speedily Eroding North Slope River Bluff Offers Window Into Ice Age Past.” Anchorage Daily News, August 29, 2016, https://www.adn.com/arctic/article/ice-rich-bluff-along-north-slope-river-eroding-fast-clip/2015/11/27/.
  21.  Romanovsky et al. (2010); Arctic Monitoring and Assessment Programme (2017); Intergovernmental Panel on Climate Change (2013), section 4.7.2.1. Permafrost temperature is measured at the depth of zero amplitude (around 20 meters below the surface).
  22.  Intergovernmental Panel on Climate Change (2013), section 4.7.2.2.
  23.  Intergovernmental Panel on Climate Change (2013), section 4.7.2.2; Arctic Monitoring and Assessment Programme (2011), section 5.3.2.1.2.
  24.  Smith et al. (2005).
  25.  Walker (2007).
  26.  Avis et al. (2011). See also appendix A.
  27.  Arctic Foundations, “Building on Thick Ice,” Alaska Business Monthly, February 2007, http://www.arcticfoundations.com/index.php/news/73-building-on-thick-ice.
  28.  G. H. Johnston, “CBD-64. Permafrost and Foundations. National Research Council Canada,” April 1965, http://web.mit.edu/parmstr/Public/NRCan/CanBldgDigests/cbd064_e.html (accessed November 12, 2018).
  29.  Wikipedia, “Construction of the Trans-Alaska Pipeline System,” https://en.wikipedia.org/wiki/Construction_of_the_Trans-Alaska_Pipeline_System (last modified September 21, 2018).
  30.  Bird (2008), p. 202.
  31.  Arctic Monitoring and Assessment Programme, SWIPA (2011), chap. 5, section 5.3.2.5.
  32.  Are et al. (2008)
  33.  Barnhart et al. (2014); Lantuit et al. (2012); Overeem et al. (2011).
  34.  Are et al. (2008).
  35.  Barnhart et al. (2014).
  36.  Jones et al. (2009); Lantuit et al. (2012); Barnhart et al. (2014).
  37.  Jones et al. (2009).
  38.  Gornitz (2013). See chapter 9 of this book for further discussion of the impacts on Arctic communities.
  39.  Schuur et al. (2015).
  40.  Mascarelli (2009).
  41.  Whiteman et al. (2013).
  42.  Brewer (2014); Shakhova et al. (2014).
  43.  Brewer (2014); Shakhova et al. (2014); Anthony et al. (2012); Vonk et al. (2012).
  44.  Anthony et al. (2012); Anthony et al. (2014); Anthony et al. (2016).
  45.  Sobek (2014); Anthony et al. (2014).
  46.  Anthony et al. (2014).
  47.  Smith et al. (2005).
  48.  Avis et al. (2011).
  49.  Vonk et al. (2012).
  50.  Olefeldt et al. (2016).
  51.  Anthony et al. (2012); Anthony et al. (2016).
  52.  Treat and Frolking (2013).
  53.  Schuur (2016).
  54.  Schuur (2016); Schuur et al. (2015).
  55.  Herndon (2018).
  56.  Gao et al. (2013). However, they did not consider greenhouse gas emissions from thermokarst or from offshore gas hydrates.
  57.  Thornton and Crill (2015).
  58.  Shakhova et al. (2010).
  59.  Ruppel and Kessler (2017).
  60.  The base of the methane hydrate stability zone appears on seismic reflection profiles as a “bottom-simulating reflector,” or BSR, which parallels the seafloor bathymetry, not the lithology or stratigraphy.
  61.  Maslin et al. (2010). Around 8,200 years ago, a massive underwater avalanche of loose sediment charged with methane gas and water cascaded abruptly down the flanks of the continental shelf and slope off the coast of Norway. The Storegga slide, one of the largest known submarine landslides, unleashed some 2,500–3,500 cubic kilometers of debris, spread over 9,500 square kilometers. It also triggered a devastating tsunami that inundated the coasts of northeastern Scotland and western Norway and dumped marine deposits up to 20 meters above sea level in the Shetland Islands. The submarine landslide and associated release of confined methane may have been triggered by icequakes resulting from glacial rebound after the melting of the Greenland Ice Sheet (see chap. 5).
  62.  Talling et al. (2014).
  63.  Shakhova et al. (2010); Shakova et al. (2014); Kort et al. (2012).
  64.  Thornton and Crill (2015).
  65.  Ruppel and Kessler (2017).
  66.  Ananthaswamy (2015).
4. DARKENING MOUNTAINS—DISAPPEARING GLACIERS
    1.  Muir, J. (1902), as quoted by Molnia et al. (2008), p. K134.
    2.  Molnia (2007).
    3.  National Oceanic and Atmospheric Administration, “Sea Level Trends,” 2017, http://tidesandcurrents.noaa.gov/sltrends/sltrends.html.
    4.  Motyka et al. (2007).
    5.  Due to local factors, for example, warm moist air from the Pacific Ocean, local microclimates, and lower mountain elevations than farther north.
    6.  Gardner et al. (2013).
    7.  Dyurgerov and Meier, in Williams and Ferrigno (2012).
    8.  Radic et al. (2014; table 1); Grinsted (2013).
    9.  Benn and Evans (2010), p. 80; Barry and Gan (2011), p. 92.
  10.  Jacka (2007), p. 507; Barry and Gan (2011), p. 104. Glide planes represent planes of weakness within ice crystals that slip more readily under pressure. They lie perpendicular to the c-axes, which tend also to be the vertical direction in a glacier. Alignment of ice crystals with this orientation imparts a characteristic crystal fabric. See also figure 1.2 and box 2.1 regarding the crystal structure of ice.
  11.  Centre for Ice and Climate, Niels Bohr Institute, “The Firn Zone: Transforming Snow to Ice,” http://www.iceandclimate.nbi.ku.dk/research/drill_analysing/cutting_and_analysing_ice_cores/analysing_gasses/firn_zone.
  12.  Bakke and Nesje (2014).
  13.  Jewelers’ rouge used to polish metals is finely powdered hematite, or iron oxide, Fe2O3. Its hardness (5–6 on the Mohs scale, where talc = 1 and diamond = 10) is somewhat less than that of most typical rock-forming minerals (Mohs hardness 6–7).
  14.  Benn and Evans (2010), pp. 62–64.
  15.  Benn and Evans (2010), p. 66.
  16.  Benn and Evans (2010), pp. 65–66.
  17.  Benn and Evans (2010), pp. 68–74; Chu (2014), pp. 33–37.
  18.  Benn and Evans (2010), pp. 77–78.
  19.  Jiskoot (2011a), p. 250.
  20.  Johnson (2013).
  21.  Jiskoot (2011a), p. 248.
  22.  See note 9 above.
  23.  Benn and Evans (2010), p. 116.
  24.  Jiskoot (2011a), pp. 248–250.
  25.  Jiskoot (2011a), pp. 248–250.
  26.  Karpilo Jr. (2009), pp. 153–156.
  27.  Jiskoot (2011b), p. 416; Barry and Gan (2011), p. 107.
  28.  European Space Agency, “Chasing Ice,” August 21, 2015, http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Chasing_ice; Chelsea Harvey, “One of the World’s Fastest Melting Glaciers May Have Just Lost Its Biggest Chunk of Ice on Record, The Washington Post, August 19, 2015, https://www.washingtonpost.com/news/energy-environment/wp/2015/08/19/one-of-the-worlds-fastest-melting-glaciers-may-have-just-lost-its-biggest-chunk-of-ice-ever/?utm_term=.4afdc3c25606.
  29.  Benn and Evans (2010), pp. 169–186; Warren (2014), pp. 105–106.
  30.  O’Leary and Christoffersen (2013).
  31.  Molnia (2007); Joughin et al. (2014); Nick et al. (2009). See also chapter 2.
  32.  Scambos et al. (2009). Ice shelves, as noted in chapter 2, are floating extensions of glaciers or ice sheets.
  33.  Benn and Evans (2010), pp. 38–39; Karpilo Jr. (2009). Ice sheet cores also preserve important archives of past climates, including information on regional temperature, precipitation, atmospheric circulation patterns, and global atmospheric composition (see chap. 7).
  34.  Grinsted (2013).
  35.  Barry and Gan (2011), p. 99.
  36.  Appendix B briefly describes some important satellite instruments used to monitor the cryosphere. An in-depth review of principles of remote sensing used in glacier and cryosphere studies is given by Tedesco, ed. (2015) and Pellikka and Rees (2010).
  37.  Raup et al. (2015), p. 133.
  38.  Raup and Kargel (2012), p. A249.
  39.  Appendix B; Pellikka and Rees (2010), pp. 16–18.
  40.  Wikipedia, “Gravity Recovery and Climate Experiment,” http://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment (last modified February 3, 2019).
  41.  Boening et al. (2012). But the upward sea level trend resumed soon thereafter.
  42.  Jacob et al. (2012).
  43.  Gardner et al. (2013).
  44.  Raup et al. (2015), p. 141, briefly summarizes how this is accomplished.
  45.  Mouginot et al. (2014); Rignot et al. (2014).
  46.  Williams and Ferrigno (2012). Individual chapters cover different glacier regions; e.g., for Alaska, chapter K, see Molnia et al. (2008).
  47.  World Glacier Monitoring Service, “Latest Glacier Mass Balance Data,” http://wgms.ch/latest-glacier-mass-balance-data/ (last updated May 16, 2018); Haeberli (2011).
  48.  Raup and Kargel (2012), pp. 247–260.
  49.  E.g., Molnia et al. (2008) for Alaska.
  50.  Pfeffer et al. (2014). Grinsted (2013) is an example of a study that derives global glacier volume from data in RGI, WGI, and GLIMS.
  51.  Johann Siegen (1921), “Glacier Tales.” Gletscherwelten/World of Glaciers. https://www.jungfraualetsch.ch/wp-content/uploads/unesco_regionalbroschuere_gletscherwelten_web.pdf.
  52.  Montagnes magique, “Cordée d’alpinistes,” by Henry George Willink (1892), https://fresques.ina.fr/montagnes/fiche-media/Montag01006/cordee-d-alpinistes.html (accessed November 12, 2018). Wilderwurm translated literally means “wild worm.”
  53.  Nussbaumer et al. (2007).
  54.  Nussbaumer et al. (2007).
  55.  Zemp et al. (2008). However, natural climate cycles, such as the decades-long Atlantic Multidecadal Oscillation (AMO), which affects climate patterns over much of the Northern Hemisphere, cause significant variations in glacier mass balance. Enhanced Alpine glacier melting, especially since the 1980s, is associated with an increasing AMO index (Huss et al., 2010).
  56.  Thompson et al. (2009).
  57.  Thompson et al. (2011).
  58.  Mouginot and Rignot (2015); Davies and Glasser (2012).
  59.  Edward Wong, “Chinese Glacier’s Retreat Signals Trouble for Asian Water Supply,” New York Times, December 9, 2015.
  60.  See also Immerzeel et al. (2010).
  61.  Brun et al. (2017).
  62.  Brun et al. (2017); Maurer et al. (2016); Bolch et al. (2012); Kääb et al. (2012).
  63.  Brun et al. (2017).
  64.  Wong, “Chinese Glacier’s Retreat.”
  65.  Zemp et al. (2015).
  66.  Kraaijenbrink et al. (2017).
  67.  Slangen et al. (2017), their table 1, including peripheral glaciers; see also appendix A.
  68.  Radic et al. (2014).
  69.  Arctic amplification is discussed in chapter 2.
  70.  Wikipedia, “Karakoram,” http://en.wikipedia.org/wiki/Karakoram (last modified October 2, 2018; accessed March 11, 2019).
  71.  Brun et al. (2017); Farinotti (2017).
  72.  Kapnick et al. (2014); Bolch et al. (2012).
  73.  Kraaijenbrink et al. (2017).
  74.  Radic et al. (2014).
5. THE GREENLAND ICE SHEET
    1.  These paleoclimate proxies include tiny marine organisms called foraminifera, sedimentary evidence from marine cores, and oxygen isotope data from Greenland ice cores.
    2.  Folger (2017).
    3.  Folger (2017).
    4.  Wikipedia, “Greenland,” http://en.wikipedia.org/wiki/Greenland (last modified October 5, 2018).
    5.  McGrath et al. (2013). “Ablation” and “equilibrium line altitude” are defined in chapter 4 and the glossary.
    6.  Tedesco et al. (2017).
    7.  Viñas (2012).
    8.  Nettles and Ekström (2010).
    9.  Quote from Huntford (1997).
  10.  Bamber et al. (2013); Morlighem et al. (2014, 2017).
  11.  Pelto (2015b).
  12.  Assuming all melted ice is spread out evenly over the ocean. See table 1.1, footnote 2 for conversion of ice mass to sea level rise.
  13.  Kjeldsen et al. (2015); Khan et al. (2014); Kjaer et al. (2012).
  14.  Velicogna et al. (2014); Moon et al. (2012).
  15.  Kjaer et al. (2012); box 5.1.
  16.  Smith (2012); Bjørk (2012).
  17.  Helm et al. (2014), table 4; Csatho et al. (2014).
  18.  Csatho et al. (2014); Moon et al. (2012).
  19.  Khan et al. (2014).
  20.  Jiang et al. (2010).
  21.  Viñas (2012).
  22.  Howat et al. (2013).
  23.  Leeson et al. (2014).
  24.  Poinar et al. (2015).
  25.  Moon et al. (2012).
  26.  An et al. (2017).
  27.  Joughin, Smith, Sheam et al. (2014).
  28.  A potential instability in a marine-terminating glacier or ice stream where the grounding line rests below sea level and the submarine topography slopes landward (see glossary).
  29.  An et al. (2017); Joughin, Smith, Sheam et al. (2014).
  30.  Khan et al. (2014).
  31.  Morlighem et al. (2014).
  32.  Morlighem et al. (2014).
  33.  The North Atlantic Current is the northern extension of the Gulf Stream. Joughin et al. (2012); Straneo and Heimbach (2013).
  34.  Holland et al. (2008).
  35.  Joughin et al. (2012); Straneo and Heimbach (2013).
  36.  Morlighem et al. (2017); Rignot et al. (2015).
  37.  Krinner and Durand (2012).
  38.  Nettles and Ekstrøm (2010).
  39.  Murray et al. (2015); Nettles and Ekström (2010).
  40.  Tedesco et al. (2017). National Oceanic and Atmospheric Administration, Arctic Program, “Arctic Report Card: Update for 2017,” http://www.arctic.noaa.gov/Report-Card/Report-Card-2017/ArtMID/.
  41.  Straneo and Heimbach (2013).
  42.  Straneo and Heimbach (2013).
  43.  Hu et al. (2011).
  44.  Harper et al. (2012); Harper (2014); Forster et al. (2014).
  45.  Forster et al. (2014).
  46.  Poinar et al. (2017).
  47.  Michael Casey, “The Case of Greenland’s Disappearing Lakes,” CBS News, January 21, 2015, https://www.cbs.news.com/news/the-case-of-greenlands-disappearing-lakes/; Howat et al. (2015).
  48.  Willis et al. (2015).
  49.  Rhonda Zurn and Lacey Nygard, “Atmospheric Warming Heats the Bottom of Ice Sheets, as Well as the Top,” January 21, 2015, https://cse.umn.edu/college/news/atmospheric-warming-heats-bottom-ice-sheets-well-top.
  50.  Stevens et al. (2015).
  51.  Stevens et al. (2015); Poinar et al. (2015).
  52.  Smith et al. (2015).
  53.  Meg Sullivan, “UCLA-Led Study Shows How Rivers of Meltwater on Greenland’s Ice Sheet Contribute to Rising Sea Levels,” January 12, 2015, http://newsroom.ucla.edu/releases/ucla-study-shows-rivers-meltwater-on-greenlands-ice-sheet-contribute-rising-sea-levels.
  54.  Lüthi (2010).
  55.  Doyle et al. (2015).
  56.  Sundal et al. (2011).
  57.  Lüthi (2013).
  58.  Nienow (2014).
  59.  Bell et al. (2014).
  60.  Bell et al. (2014).
  61.  Bamber et al. (2013). Steve Cole, George Hale, and Hannah Johnson, “NASA Data Reveals Mega-Canyon Under Greenland Ice Sheet,” NASA, August 29, 2013, https://www.nasa.gov/press/2013/august/nasa-data-reveals-mega-canyon-under-greenland-ice-sheet/#.W7kW2_ZRfIU (accessed July 27, 2015).
  62.  Morlighem et al. (2014).
  63.  Morlighem et al. (2014).
  64.  Morlighem et al. (2017).
  65.  Cooper et al. (2016).
  66.  Rogozhina et al. (2016). Iceland is located on the mid-Atlantic Ridge which separates the North American plate from the Eurasian plate. According to plate tectonic theory, the midocean ridge system, which encircles the globe, is where magma ascends from the upper mantle, which helps drive the plates apart. Furthermore, Iceland sits atop a long-lived “hot spot” of anomalously warm magma that has built up the island over time. Tens of millions of years ago Greenland lay over the Icelandic hot spot, but has subsequently drifted northwestward as the plates have spread apart.
  67.  As cited by Eric Holtaus, “Slate Exclusive: Why Greenland’s ‘Dark Snow’ Should Worry You,” Future Tense (column), Slate.com, September 16, 2014, http://www.slate.com/blogs/future_tense/2014/09/16/jason_box_s_research_into_greenland_s_dark_snow_raises_more_concerns_about.html (accessed August 5, 2015).
  68.  E.g., Stibal et al. (2017); Tedesco et al. (2016); Howat et al. (2013).
  69.  Leeson et al. (2014).
  70.  Tedesco et al. (2016).
  71.  Wientjes et al. (2011).
6. ANTARCTICA: THE GIANT ICE LOCKER
    1.  Secretariat of the Antarctic Treaty, “The Antarctic Treaty,” http://www.ats.aq/e/ats.htm.
    2.  This portion of the treaty is up for review in 2048. A new race to the South Pole may then unfold, as nations compete for increasingly scarce critical mineral resources and as technological advances and improving climate conditions make resource exploitation there more feasible (more in chap. 9). S. Romero, “Array of Players Joining Race for Space at Bottom of the World,” New York Times, December 30, 2015.
    3.  Ford (2015).
    4.  IceCube, South Pole Neutrino Laboratory, “Antarctic Weather,” https://icecube.wisc.edu/pole/weather/.
    5.  Ford (2015).
    6.  Benn and Evans (2010), p. 210.
    7.  Rignot et al. (2013).
    8.  Barry and Gan (2011), pp. 278–279.
    9.  NASA, Earth Observatory, “Pine Island Glacier Births New ’Berg,” September 28, 2017, https://earthobservatory.nasa.gov/images/91066/pine-island-glacier-births-new-berg (accessed May 3, 2018).
  10.  NASA, Earth Observatory, “Drifting with Ice Island B31,” November 18, 2013, https://earthobservatory.nasa.gov/IOTD/view.php?id=83519 (accessed May 10, 2018).
  11.  Jeong et al. (2016).
  12.  National Science Foundation Press Release 11–247, “Antarctica’s Gamburtsev Subglacial Mountains Mystery Solved,” November 16, 2011, https://www.nsf.gov/news/news_summ.jsp?cntn_id=122290 (accessed September 13, 2013).
  13.  Fretwell et al. (2013).
  14.  Mount Erebus and Mount Terror were named after the ships on Captain Franklin’s ill-fated Arctic expedition (see chaps. 1 and 2). Wikipedia, “Mount Erebus,” https://en.wikipedia.org/wiki/Mount_Erebus (last modified September 20, 2018).
  15.  Van Wyk de Vries et al. (2017).
  16.  Lough et al. (2013).
  17.  Schroeder et al. (2014).
  18.  Some dispute this early date for the first cyanobacteria, placing their origin closer to the “Great Oxidation Event” around 2.5 billion years ago, when atmospheric oxygen levels began to rise (e.g., Rasmussen et al., 2008).
  19.  Wikipedia, “Blood Falls,” https://en.wikipedia.org/wiki/Blood_Falls (last modified September 9, 2018).
  20.  Ehlmann and Edwards (2014). The discovery of perchlorate in the soils of the Dry Valleys also reinforces the resemblance to Mars. Perchlorate has been found near the South Pole of Mars and by the Curiosity rover now exploring the Gale Crater (Tamparri et al., 2010; King (2015).
  21.  Corrigan (2011); Hobart M. King, “Hunting Meteorites in Antarctica,” Geology.com, http://geology.com/stories/13/antarctica-meteorites/ (accessed January 21, 2016).
  22.  Bell et al. (2011).
  23.  Shtarkman et al. (2013).
  24.  Wright and Siegert (2012).
  25.  Rignot et al. (2011).
  26.  Bell (2008a); Bell (2008b).
  27.  Wright and Siegert (2012).
  28.  Wingham et al. (2006).
  29.  Bell (2008b).
  30.  Tulaczyk and Hossainzadeh (2011); Bell et al. (2011).
  31.  Zwally et al. (2015).
  32.  Eric Mack, “Is Antarctica Gaining or Losing Ice? It’s Both,” Forbes, November 4, 2015, https://www.forbes.com/sites/ericmack/2015/11/04/yes-antarctica-is-both-gaining-and-losing-ice-but-really-losing-it/#1b092e309301/ (accessed January 22, 2016).
  33.  Altimetry: McMillan et al. (2014); Zwally et al. (2015). GRACE gravimetry: Sasgen et al. (2013); Harig and Simons (2015); table 6.1; also chap. 4, appendix B.
  34.  See also chapter 2; Joughin and Alley (2011); Joughin et al. (2012); Alley et al. (2015).
  35.  Mouginot et al. (2014).
  36.  Sutterley et al (2014).
  37.  Thomas Summer, “West Antarctic Ice Sheet Is Collapsing,” Science News, May 12, 2014, https://www.sciencemag.org/news/2014/05/west-antarctic-ice-sheet-collapsing (accessed November 13, 2018).
  38.  Rignot et al. (2014).
  39.  Joughin et al. (2014).
  40.  Favier et al. (2014); Joughin, Smith, and Medley (2014).
  41.  Konrad et al. (2018).
  42.  Christie et al. (2016). The grounding line of the ice stream feeding the Venable Ice Shelf has held fast, in spite of considerable ice shelf thinning since the 1990s. This shelf may be stuck on underwater “pinning points” that act as brakes on ice motion.
  43.  Feldmann and Levermann (2015). The marine-based portion of the WAIS is that grounded below present sea level.
  44.  Joughin, Smith, and Medley (2014).
  45.  Alley et al. (2015).
  46.  Whereby a rapidly eroding stream cuts back across the drainage divide and captures the flow of another stream.
  47.  Feldmann and Levermann (2015).
  48.  Millan et al. (2017).
  49.  Paolo et al. (2015); Rignot et al. (2013, 2014); Depoorter et al. (2013); Pritchard et al. (2012).
  50.  Rignot et al. (2013); Depoorter et al. (2013).
  51.  See glossary; chap. 2, “Undermining Ice Shelves.”
  52.  Schmidtko et al. (2014).
  53.  Pollard et al. (2015).
  54.  MacGregor et al. (2012); Pollard et al. (2015).
  55.  Alley et al. (2016).
  56.  Bell et al. (2017); Kingslake et al. (2017).
  57.  Pritchard et al. (2012).
  58.  Thinning ice shelves: Pritchard et al. (2012); Rignot et al. (2013); Depoorter et al. (2013); Paolo et al. (2015). Grounding line retreat and ice discharge: Konrad et al. (2018); Mouginot et al. (2014); Rignot et al. (2014); Joughin, Smith, and Medley (2014); Favier et al. (2014); Sutterley et al. (2014).
  59.  Fürst et al. (2016).
  60.  Jamieson et al. (2012).
  61.  Robel et al. (2016).
  62.  Gomez et al. (2015).
  63.  Gomez et al. (2015).
  64.  Barry and Gan (2011), p. 2. The total mass of ice on the WAIS is equivalent to a ~5-meter SLR. The oft-cited statement that complete melting of the WAIS would raise sea level by ~3.3 meters refers to the ice mass subject to MISI. Around 1.8 meters SLR equivalent would survive any likely warming event.
  65.  Rignot et al. (2013); Pritchard et al. (2012); Paolo et al. (2015).
  66.  Qiu (2017).
  67.  Fretwell (2015); Greenbaum et al. (2015).
  68.  Rintoul et al. (2016).
  69.  Greenbaum et al. (2015).
  70.  Li et al. (2015).
  71.  Mengel and Levermann (2014).
7. FROM GREENHOUSE TO ICEHOUSE
    1.  Eberle and Greenwood (2012).
    2.  DeConto et al. (2008); Galeotti et al. (2016).
    3.  DeConto et al. (2008); Galeotti et al. (2016).
    4.  Miller et al. (2011).
    5.  Levy et al. (2016).
    6.  Salzmann et al. (2016).
    7.  Bo et al. (2009).
    8.  Araucariaceae are a family of tall evergreen coniferous trees with spirally arranged needles or broad, flat leaves. They generally occur in Southern Hemisphere tropical or semitropical forests, although some species are also found in drier scrubland. More familiar examples include the monkey puzzle tree and Norfolk Island pine. The colorful 200-million-year-old petrified logs of Petrified Forest National Park in northern Arizona were members of a related, now-extinct species.
    9.  Naish et al. (2009).
  10.  Rovere et al. (2014); Rowley et al. (2013); Miller et al. (2012). (Estimates range between 10 and 30 meters higher than present sea levels.)
  11.  See glossary; also discussion in chapter 6, under “Maybe Not So Fast!”
  12.  Tibet stays cool in summer because of its high elevation. Yet it remains the warmest spot on Earth at that altitude. This warm spot sets up a continent-scale circulation akin to land and sea breezes. During summer, the zone of highest mean surface temperatures shifts north. Moisture from the Indian Ocean replaces the hot, dry air over the Tibetan plateau. As the moist air approaches the Himalayas, it rises, cools, and falls as rain over India and along the southern slopes of the Himalayas. By the time the monsoon passes over this topographic barrier, the air has dried out, leaving Tibet a near-desert. The uplift of the Himalayas has intensified this circulation pattern.
  13.  Raymo and Ruddiman (1992).
  14.  Kent and Muttoni (2013).
  15.  Livermore et al. (2007).
  16.  Stickley et al. (2004); Lyle et al. (2007).
  17.  Haug et al. (2004); O’Dea et al. (2016).
  18.  Lear and Lunt (2016).
  19.  Dutton et al. (2015); Foster and Rohling (2013); Grant et al. (2012).
  20.  DeConto et al. (2008); Galeotti et al. (2016).
  21.  Triparti et al. (2009).
  22.  Schneider and Schneider (2010).
  23.  See note 9.
  24.  DeConto et al. (2008).
  25.  Bierman et al. (2014); “2.7-Million-Year-Old Forested Landscape Discovered Under Greenland Ice Sheet,” Sci News, April 17, 2014, http://www.sci-news.com/geology/science-forested-landscape-greenland-ice-sheet.
  26.  The half-life of 10Be is 1.4 million years, the time needed for half a given quantity of the isotope to decay. (The presumed age of the oldest ice is around two half-lives of 10Be.)
  27.  Lamont-Doherty Earth Observatory, “Most of Greenland Ice Melted to Bedrock in Recent Geologic Past, Study Says,” December 7, 2016, https://www.ldeo.columbia.edu/news-events/most-greenland-ice-melted-bedrock-recent-geologic-past-study-says.
  28.  Steig and Wolfe (2008).
  29.  Dutton et al. (2015); Grant et al. (2012); Rohling et al. (2009).
  30.  Kerr (2013).
  31.  Maslin and Brierley (2015).
  32.  Brook (2008).
  33.  Galeotti et al. (2016).
  34.  Naish et al. (2009).
  35.  Cook et al. (2013).
  36.  Dutton et al. (2015).
  37.  Raymo and Mitrovica (2012).
  38.  Reyes et al. (2014).
  39.  The volume of the Greenland Ice Sheet is ~7 meters (23 feet) of sea level equivalent. Melting of the entire WAIS would raise sea level by ~5 meters (16 feet). The portion of WAIS ice grounded below sea level and subject to the marine ice sheet instability would yield only ~3.3 (11 feet) meters.
  40.  Dutton et al. (2015); Kopp et al. (2009), after correcting for glacial isostatic, gravitational, and rotational effects.
  41.  O’Leary et al. (2013).
  42.  Rohling et al. (2008).
  43.  Barlow et al. (2018).
  44.  Colville et al. (2011).
  45.  Quoted in Schiermeier (2013).
  46.  MacGregor et al. (2015).
  47.  NEEM (North Greenland Eemian Ice Core Drilling) (2013); Colville et al. (2011); Kopp et al. (2009).
  48.  Carlson and Clark (2012).
  49.  Mackintosh et al. (2011).
  50.  Weber et al. (2014).
  51.  Hillenbrand et al. (2013).
  52.  Evans (2015).
  53.  Carlson and Clark (2012); Deschamps et al. (2012).
  54.  Liu et al. (2016).
  55.  Carlson and Clark (2012); Li et al. (2012).
8. RETURN TO THE GREENHOUSE
    1.  The percentage of freshwater may be closer to 77 percent (Barry and Gan, 2011, p. 3).
    2.  Walker (2013).
    3.  Archer and Brovkin (2008).
    4.  National Snow & Ice Data Center, “2017 Ushers In Record Low Extent,” February 7, 2017, http://nsidc.org/arcticseaicenews/2017/02/2017-ushers-in-record-low-extent/ (accessed February 17, 2017); Andrea Thompson, “Sea Ice Hits Record Lows at Both Poles,” Scientific American, February 13, 2017, https://www.scientificamerican.com/article/sea-ice-hits-record-lows-at-both-poles/ (accessed February 20, 2017); Scott Sutherland, “North Pole Temps Spiked by Nearly 30 Celsius Last Week,” The Weather Network, February 13, 2017, https://www.theweathernetwork.com/news/articles/arctic-storms-bring-another-winter-heatwave-to-north-pole/79190 (accessed February 20, 2017).
    5.  Hogg and Gudmundsson (2017); Viñas (2017).
    6.  Archer (2009).
    7.  DeConto and Pollard (2016); Pollard et al. (2015).
    8.  Ritz et al. (2015).
    9.  Vermeer and Rahmstorf (2009); Rahmstorf (2007).
  10.  Joughin, Smith, and Medley (2014).
  11.  Golledge et al. (2015); Sutter et al. (2016).
  12.  Feldmann and Levermann (2015).
  13.  Khan et al. (2014).
  14.  Gomez et al. (2015).
  15.  Robinson et al. (2012).
  16.  Golledge et al. (2015).
  17.  DeConto and Pollard (2016).
  18.  Wikipedia, “Svante Arrhenius,” https://en.wikipedia.org/wiki/Svante_Arrhenius (last modified October 11, 2018; accessed February 14, 2017).
  19.  Intergovernmental Panel on Climate Change (2013a), chap. 12, box 12.2, p. 1110.
  20.  NASA, Global Climate Change, “Carbon Dioxide,” https://climate.nasa.gov/vital-signs/carbon-dioxide/; CO2.Earth, http://co2.earth. See also fig. 1.7.
  21.  NASA, Goddard Institute for Space Studies, “NASA, NOAA Data Show 2016 Warmest Year on Record Globally,” January 18, 2017, https://www.giss.nasa.gov/research/news/20170118/ (accessed February 15, 2017). While not record-setting, 2018 was the fourth warmest in the global historic record. G. A. Schmidt and D. Arndt, “NOAA/NASA Annual Global Analysis for 2018,” https://www.giss.nasa.gov/research/news/20190206/201902briefing.pdf (accessed February 7, 2019).
  22.  On February 8, 2017, New York City basked in unseasonable, record-shattering, mild 60°–65°F weather; by early the next morning, temperatures had plunged to the upper 20s Fahrenheit and 8–12 inches of snow covered the city.
  23.  Clark et al. (2016).
  24.  UNFCCC, “The Paris Agreement,” http://unfccc.int/paris_agreement/items/9485.php (accessed February 16, 2017).
  25.  Hansen et al. (2008). The 2°C limit has been urged by many climate scientists, based on anticipated impacts, and has been adopted by the UNFCCC as a target in the current Paris Agreement.
  26.  For starters, see chapter 10 in Gornitz (2013).
  27.  Such a lengthy safe storage period—almost the duration of the Holocene, the epoch following the last ice age—is needed to cool down the radioactive waste products.
  28.  See, for example, Rosenzweig et al. (2018) and case studies therein.
9. THE IMPORTANCE OF ICE
    1.  NASA, Goddard Institute for Space Studies, “NASA, NOAA Data Show 2016 Warmest Year on Record Globally,” January 18, 2017, https://www.giss.nasa.gov/research/news/20170118/ (accessed May 30, 2017).
    2.  National Snow & Ice Data Center, “2017 Ushers In Record Low Extent,” February 7, 2017, http://nsidc.org/arcticseaicenews/2017/02/2017-ushers-in-record-low-extent/ (accessed February 17, 2017); Scott Sutherland, “North Pole Temps Spiked by Nearly 30 Celsius Last Week,” The Weather Network, February 13, 2017, https://www.theweathernetwork.com/news/articles/arctic-storms-bring-another-winter-heatwave-to-north-pole/79190 (accessed February 20, 2017).
    3.  National Oceanic and Atmospheric Administration, “Unprecedented Arctic Weather Has Scientists on Edge,” February 17, 2017, http://www.noaa.gov/news/unprecedented-arctic-weather-has-scientists-on-edge (accessed February 23, 2017).
    4.  Derocher (2008).
    5.  Struzik (2009).
    6.  Mele and Victor (2016); Goode (2016).
    7.  Pilkey et al. (2016).
    8.  Wikipedia, “Polar Bear,” https://en.wikipedia.org/wiki/Polar_bear (last modified September 19, 2018; accessed May 31, 2017).
    9.  See glossary.
  10.  National Snow & Ice Data Center, “Arctic Sea Ice Maximum at Second Lowest in the Satellite Record,” March 23, 2018, http://nsidc.org/arcticseaicenews/2018/03/arctic-sea-ice-maximum-second-lowest/ (accessed April 24, 2018); National Snow & Ice Data Center, “Arctic Sea Ice Maximum at Record Low for Third Straight Year,” March 22, 2017, https://nsidc.org/news/newsroom/arctic-sea-ice-maximum-record-low-third-straight-year/ (accessed May 25, 2017); National Snow & Ice Data Center, “2016 Ties with 2007 for Second Lowest Arctic Sea Ice Minimum,” September 16, 2016, http://nsidc.org/arcticseaicenews/2016/09/2016-ties-with-2007-for-second-lowest-arctic-sea-ice-minimum/ (accessed September 16, 2016).
  11.  “Arctic Sea Ice Maximum at Second Lowest in the Satellite Record.”
  12.  Theroux (2016).
  13.  E.g., Pongracz et al. (2017).
  14.  Morello (2010).
  15.  Quoted in Rosen (2017).
  16.  United Nations Environment Programme (2007).
  17.  Ehrlich (2010), pp. 30, 69.
  18.  Ehrlich (2010), pp. 216, 241.
  19.  Boelman (2011).
  20.  Struzic (2011).
  21.  Miller and Ruiz (2014).
  22.  Quoted in Rosen (2017).
  23.  Cohen et al. (2014); Masters (2014).
  24.  Overland et al. (2016).
  25.  Gillis and Fountain (2016); Vaidyanathan and Patterson (2015).
  26.  Gautier et al. (2009).
  27.  Wikipedia, “Klondike Gold Rush,” https://en.wikipedia.org/wiki/Klondike_Gold_Rush (last modified October 4, 2018; accessed June 13, 2017).
  28.  Shigley et al. (2016).
  29.  Shigley et al. (2016).
  30.  “A New Perfection Found in Diamonds Created by an Asteroid in Siberian Crater 35 Million Years Ago,” Siberian Times, September 16, 2013, http://siberiantimes.com/science/casestudy/features/a-new-perfection-found-in-diamonds-created-by-an-asteroid-in-siberian-crater-35-million-years-ago/ (accessed June 15, 2017).
  31.  Gautier et al. (2009).
  32.  Wikipedia, “Natural Resources of the Arctic,” https://en.wikipedia.org/wiki/Natural_resources_of_the_Arctic (last modified May 14, 2018; accessed June 20, 2017).
  33.  Glasby and Voytekhovshy (2009).
  34.  Jennifer Kingsley, “When Coal Leaves Center Stage in Longyearbyen,” Arctic Deeply (archive), News Deeply, March 3, 2016, https://www.newsdeeply.com/arctic/articles/2016/03/03/when-coal-leaves-center-stage-in-longyearbyen (accessed June 21, 2017).
  35.  Kingsley, “When Coal Leaves Center Stage in Longyearbyen.” See also Wikipedia, “Natural Resources of the Arctic.”
  36.  Wikipedia, “Red Dog Mine,” https://en.wikipedia.org/wiki/Red_Dog_mine (last modified September 4, 2018; accessed June 21, 2017).
  37.  Wikipedia, “Mary River Mine,” https://en.wikipedia.org/wiki/Mary_River_Mine (last modified September 28, 2018); Baffinland, “Who We Are,” http://www.baffinland.com/about-us/who-we-are/?lang=en; Nick Murray, “Baffinland Iron Mines’ Phase 2 Plan Gets Sent Back to Nunavut Planning Commission,” CBC News, December 20, 2016, http://www.cbc.ca/news/canada/north/nirb-baffinland-phase-2-planning-commission-1.3904189 (accessed June 21, 2017).
  38.  Wikipedia, “Mary River Mine.” https://en.wikipedia.org/wiki/Mary_River_Mine (last updated November 15, 2018; accessed November 16, 2018); Nunatsiaq News, “Nunavut Board to Finish with Mary River Railway Proposal by June 2019,” Nunatsiaq News, October 17, 2018. http://nunatsiaq.com/stories/article/65674nunavut_board_to_finish_with_mary_river_railway_proposal_by_june_2019/.
  39.  Gray (2016)
  40.  Haecker (2016).
  41.  Av Mieke Coppes, “No More Crystal Serenity in the Northwest Passage,” High North News, December 13, 2017, http://www.highnorthnews.com/no-more-crystal-serenity-in-the-northwest-passage/ (accessed March 5, 2018); Jane George, “Norwegian Cruise Company Plans Northwest Passage Transit with Hybrid Vessel,” Nunatsiaq News, December 11, 2017, http://nunatsiaq.com/stories/article/65674norwegian_cruise_company_plans_nw_passage_transit_with_hybrid_vessel/ (accessed March 5, 2018).
  42.  Arctic Monitoring and Assessment Programme (2017); Overland and Wang (2013).
  43.  Lulu (2017).
  44.  Miller and Ruiz (2014).
  45.  Schiffman (2016).
  46.  Clearly, it’s much more complex than that. Chapter 4 discusses the glacial retreat more fully.
  47.  Harriman (2013).
  48.  Saavedra et al. (2018).
  49.  Navab (2011); Bradley et al. (2006).
  50.  Pritchard (2017).
  51.  Laghari (2013).
  52.  Bolch (2017); Pritchard (2017).
  53.  Immerzeel et al. (2010).
  54.  Huss and Hock (2018); Kraaijenbrink et al. (2017); Immerzeel et al (2010).
  55.  Huss and Hock (2018); Kraaijenbrink et al., 2017.
  56.  Huss and Hock (2018); appendix A.
  57.  Huss and Hock (2018); appendix A.
  58.  Fyfe et al. (2017).
  59.  Fyfe et al. (2017).
  60.  Sierra Nevada Conservatory, “California’s Primary Watershed,” 2011, http://www.sierranevada.ca.gov/our-region/ca-primary-watershed; California-Nevada Climate Applications Program (CNAP), “Sierra Nevada Snowpack,” March 2016, https://www.swcasc.arizona.edu/sites/default/files/Snowpack.pdf/ (both accessed December 3, 2018).
  61.  Natural Resources Defense Council (NRDC), “California Snowpack and the Drought,” fact sheet, April 2014, https://www.nrdc.org/sites/default/files/ca-snowpack-and-drought-FS.pdf (accessed August 18, 2017).
  62.  Larson (2015).
  63.  Between 1880 and 2015. Swiss Academy of Sciences, “Welcome to the Glacier Monitoring in Switzerland (GLAMOS),” http://glaciology.ethz.ch/messnetz/ (accessed August 10, 2017).
  64.  Fischer et al. (2014).
  65.  Tagliabue (2013).
  66.  Huggel et al. (2012); Tagliabue (2013).
  67.  Keane (2017).
  68.  Clague et al. (2012).
  69.  McGuire (2012), p. 245.
  70.  Huggel et al. (2012); Tagliabue (2013).
  71.  Horstmann (2004).
  72.  Veh et al. (2018).
  73.  McGuire (2012), p. 264. See also Nettles and Ekström (2010), cited in chap. 5.
  74.  Van Wyk de Vries et al. (2017); Schroeder et al. (2014).
  75.  Intergovernmental Panel on Climate Change (2013a), chap. 13, table 13.5, p. 1182 (RCP8.5, 2081–2100). See appendix A for explanation of RCP scenarios.
  76.  DeConto and Pollard (2016). See also Pollard et al. (2015).
  77.  Carbognin et al. (2009).
  78.  Sweet et al. (2014).
  79.  Strauss et al. (2016).
  80.  Blake et al. (2011).
  81.  Orton et al. (2016).
  82.  Special Initiative for Rebuilding and Resiliency (2013).
  83.  National Oceanic and Atmospheric Administration (2017).
  84.  Neumann et al. (2015).
  85.  Hauer et al. (2016).
  86.  Gornitz (2018).
  87.  Morton et al. (2004).
  88.  Gornitz (2013), chap. 8, pp. 188–190.
  89.  Gornitz (2013), chap. 9.
  90.  E.g., Aerts et al. (2009).
  91.  Rotterdam Climate Initiative (2010).
  92.  Stalenberg (2012).
  93.  When Canal Street lived up to its name. Originally a “sluggish stream,” it became a ditch to drain local swamps. It soon turned into a stinking sewer, was covered, and by 1820, Canal Street was built over it. Wikipedia, “Canal Street (Manhattan),” https://en.wikipedia.org/wiki/Canal_Street_(Manhattan) (last modified July 27, 2018; accessed July 27, 2017).
  94.  Nordenson et al. (2010).
  95.  Lafarge Holcim Foundation, “The Dryline: Urban Flood Protection Infrastructure,” http://lafargeholcim-foundation.org/projects/the-dryline (accessed June 7, 2016).
  96.  Mele and Victor (2016).
  97.  Goode (2016).
  98.  De Melker and Saltzman (2016).
  99.  Green (2016); Hino et al. (2017).
100.  Hauer (2017).
101.  Hino et al. (2017).
102.  Polar night affects all areas north of the polar circle (66.5°N) to some extent. The duration of polar night increases with latitude, reaching 6 months of the year at the North Pole. But conversely, the pole experiences six months of sunlight during the second half of the year. Farther south, there may be several hours of dim twilight, even when the sun lies below the horizon, because of the way the atmosphere bends the rays of light.
APPENDIX A. ANTICIPATING FUTURE CLIMATE CHANGE
    1.  Intergovernmental Panel on Climate Change (2013a).
    2.  A negative surface mass balance (SMB) implies that ice losses (surface melting, runoff, and sublimation [ice to water vapor]) exceed accumulation (snowfall). See glossary.
APPENDIX B. EYES IN THE SKY—MONITORING THE CRYOSPHERE FROM ABOVE
    1.  NASA, “The Landsat Program,” https://landsat.gsfc.nasa.gov/; USGS, “Landsat Missions,” https://landsat.usgs.gov/ (accessed January 18, 2018).
    2.  NASA, “Landsat 8,” https://landsat.gsfc.nasa.gov/landsat-data-continuity-mission/; USGS, “Landsat Missions: Imaging the Earth Since 1972,” https://landsat.usgs.gov/landsat-missions-timeline (accessed January 18, 2018).
    3.  Satellite Imaging Corp., “Satellite Sensors (0.31m–2m),” https://www.satimagingcorp.com/satellite-sensors/.
    4.  USGS, Land Processes Distributed Active Archive Center, “ASTER Overview,” https://lpdaac.usgs.gov/dataset_discovery/aster/ (accessed January 9, 2017); https://lpdaac.user_resources/data_in_action/global_land_ice_measurements_space_observing_glaciers (accessed January 30, 2018).
    5.  Raup and Kargel (2012), p. A249.
    6.  NASA, “MODIS Web, Design Concept,” https://modis.gsfc.nasa.gov/about/design.php/; NASA, Terra, “MODIS,” https://terra.nasa.gov/about/terra-instruments/modis/ (accessed January 9, 2018).
    7.  NASA, “ICESat-2: Instrument,” http://icesat.gsfc/nasa/gov/icesat2/instrument.php; NASA, ICESat-2, “Science,” https://icesat-2.gsfc.nasa.gov/science/ (accessed January 9, 2017).
    8.  NASA, “IceBridge,” https://www.nasa.gov/mission_pages/icebridge/index.html (accessed January 9, 2018).
    9.  Wikipedia, “Special Sensor Microwave/Imager,” https://en.wikipedia.org/wiki/Special_sensor_microwave/imager (last modified May 27, 2018; accessed February 12, 2019).
  10.  For more mission details, see http://www.jpl.nasa.gov, https://sealevel.jpl.nasa.gov/missions/jason3/, and http://www.cnes.fr.
  11.  NASA, “Understanding Sea Level; Key Indicators; Global Mean Sea Level,” https://sealevel.nasa.gov/understanding-sea-level/key-indicators/global-mean-sea-level (covers January 1993 to October 9, 2017; accessed January 5, 2018); CNES/Aviso+, “Mean Sea Level Rise,” https://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level.html (sea level rise plot covers January 5, 1993, to November 17, 2017; accessed February 5, 2018).
  12.  European Space Agency, “Overview,” November 6, 2013, https://earth.esa.int/web/guest/missions/esa-eo-missions/cryosat/mission-summary (accessed January 31, 2018).
  13.  SIRAL Altimeter. https://www.aviso.altimetry.fr/en/missions/current-missions/cryosat/instruments/siral.html/ (accessed November 27, 2018).
  14.  European Space Agency, Copernicus, “Synthetic Aperture Radar Missions,” http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/SAR_missions/ (accessed January 31, 2018).
  15.  Geoimage, “TerraSAR-X,” https://www.geoimage.com.au/satellite/TerraSar/ (accessed January 31, 2018).
  16.  Canadian Space Agency, “RADARSAT-2,” December 14, 2017, http://www.asc.gc.ca/eng/satellites/radarsat2/default.asp/; http://www.asc-csa.gc.ca/eng/satellites/radarsat/radarsat-tableau.asp (both accessed Nov. 27, 2018).
  17.  Wikipedia, “Gravity Recovery and Climate Experiment,” http://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment (last modified February 3, 2019; accessed February 12, 2019).