Little Ice Age (LIA) glacier perimeters - derived from moraine evidence visible in satellite imagery. 1966, 1998, 2005, 2015 glacier perimeters - derived from aerial and satellite imagery. These data represent a time series of the 37 named glaciers of Glacier National Park, MT, USA and two named glaciers in the Flathead National Forest. The glacier’s maximum extent during the peak of the Little Ice Age (mid-nineteenth century) was determined from morainal evidence visible in satellite imagery from 2014/2015/2016. Glacier margins were digitized from aerial imagery taken in 1966, 1998, and 2005, and from satellite imagery acquired in 2015/2016. Late summer imagery was used for analysis so that the extent of glacial ice was most easily determined after seasonal snow had melted from the glacier surface. Comparison between years shows a reduction in area from LIA extent to 2015/6 for all glaciers, although rates of loss are variable. The 2015 data reveal that 26 glaciers remain that are larger than 25 acres (0.1 square kilometer), which is used as a guideline for deciding if bodies of ice are large enough to be considered glaciers. Morainal evidence indicates that an estimated 146 glaciers existed in Glacier National Park during the Little Ice Age (LIA). Establishing rates of glacier retreat, using the decreasing area of glacier ice, is key to understanding the Glacier National Park ecosystem and future state of resources. For instance, glacial meltwater provides critical habitat for endangered stream insects. More broadly, retreating glaciers are indicative of long term climate change and have hydrologic and ecologic importance to many park resources. Glaciers and their retreat are of great interest to park visitors and the American public and are part of Glacier National Park's appeal. Information on appropriate use of these data and a description of the time series analysis is available at the USGS glacier time series web page: https://www.usgs.gov/centers/norock/science/time-series-glacier-retreat Other Resources: Endangered stream insects: https://www.usgs.gov/staff-profiles/joe-giersch?qt-staff_profile_science_products=3#qt-staff_profile_science_products Glacier retreat: https://www.usgs.gov/centers/norock/science/retreat-glaciers-glacier-national-park?qt-science_center_objects=0

Glacier Name - GNP	Area LIA (m2)	Area 1966 (m2)	Area 1998 (m2)	Area 2005 (m2)	Area 2015 (m2)	% Decrease 1850-2015
Agassiz Glacier	4,246,977.56	1,600,559.73	1,174,485.68	1,039,612.34	736,669.75	82.65
Ahern Glacier	765,116.39	589,185.63	516,658.66	511,939.47	511,589.79	33.14
Baby Glacier*	136,133.57	117,171.13	80,880.38	76,006.47	75,562.60	44.49
Blackfoot Glacier^	4,970,064.26	1,832,451.35	1,625,124.38	1,630,173.41	1,498,505.92	69.85
Boulder Glacier*	829,577.99	231,017.73	48,774.13	45,803.63	35,298.01	95.75
Carter Glacier	708,091.34	355,743.44	269,013.88	234,414.36	224,773.89	68.26
Chaney Glacier	1,078,922.83	563,819.03	430,372.02	359,686.58	334,484.90	69.00
Dixon Glacier	671,001.22	291,142.05	166,983.60	162,669.91	125,831.13	81.25
Gem Glacier*	24,364.74	29,140.12	23,756.51	23,527.27	22,156.68	9.06
Grinnell Glacier^	1,976,494.97	1,020,200.39	715,907.79	615,568.81	563,720.29	71.48
Harris Glacier*	79,286.24	148,501.60	40,263.73	38,969.10	34,260.89	56.79
Harrison Glacier	3,470,484.89	2,059,376.84	1,846,232.52	1,697,714.47	1,661,456.75	52.13
Herbst Glacier*	343,244.32	170,234.16	50,794.78	40,856.01	31,886.02	90.71
Hudson Glacier*	132,164.98	90,213.45	55,762.11	52,269.76	52,167.62	60.53
Ipasha Glacier	594,065.79	328,608.60	228,254.45	195,800.97	194,738.75	67.22
Jackson Glacier^	3,094,285.19	1,280,508.24	811,857.45	803,342.15	756,864.10	75.54
Kintla Glacier	2,780,343.02	1,309,016.20	972,884.73	931,213.70	877,726.05	68.43
Logan Glacier	694,335.54	503,361.09	387,547.07	367,936.17	219,016.92	68.46
Lupfer Glacier*	171,200.25	126,375.83	66,661.16	63,843.53	73,274.68	57.20
Miche Wabun	263,262.30	204,468.79	111,127.26	107,464.55	103,616.92	60.64
North Swiftcurrent Glacier*	227,306.21	116,675.97	84,546.10	90,181.52	86,305.30	62.03
Old Sun Glacier	499,662.38	421,347.41	349,137.54	346,751.63	341,077.95	31.74
Piegan Glacier	311,173.34	280,151.62	265,084.78	250,768.05	244,307.08	21.49
Pumpelly Glacier	1,978,996.13	1,006,469.53	910,631.86	908,834.15	902,787.30	54.38
Rainbow Glacier	1,910,417.47	1,430,411.36	1,120,814.92	1,089,977.46	1,053,376.03	44.86
Red Eagle*	477,070.90	134,709.82	77,923.58	77,923.53	63,685.24	86.65
Salamander Glacier^	250,056.48	229,028.19	181,688.65	173,617.99	176,108.77	29.57
Sexton Glacier	528,179.20	400,493.53	324,011.87	312,762.43	298,681.73	43.45
Shepard Glacier*	497,244.16	250,678.82	91,584.19	75,248.66	70,739.49	85.77
Siyeh Glacier	378,010.17	306,295.75	214,597.44	214,663.20	205,386.48	45.67
Sperry Glacier	3,793,322.12	1,339,531.54	953,104.43	888,095.13	801,670.14	78.87
Swiftcurrent Glacier	594,231.70	221,786.00	188,681.39	176,239.36	170,348.10	71.33
Thunderbird Glacier	1,075,097.51	135,074.71	121,885.69	115,978.22	107,012.09	90.05
Two Ocean Glacier*	1,076,919.16	429,001.73	193,677.91	189,199.44	75,172.89	93.02
Vulture Glacier	811,528.41	408,034.38	336,924.77	329,180.45	296,786.09	63.43
Weasel Collar Glacier	809,813.09	558,088.21	507,418.42	506,575.45	499,734.76	38.29
Whitecrow Glacier	741,530.93	242,488.01	124,759.84	112,799.23	103,824.86	86.00
Total GNP	42,989,976.75	20,761,361.98	15,669,815.67	14,857,608.56	13,630,605.96	68.29
Glacier Name - FNF
Grant Glacier**	842,943.74	347,753.17	288,223.64	285,758.27	279,157.80	66.88
Stanton Glacier**	950,202.24	532,357.36	315,177.77	301,630.87	268,967.55	71.69
Total FNF	1,793,145.98	880,110.53	603,401.41	587,389.14	548,125.35	69.43

* based on 2015 data, this glacier is no longer considered "active" because its area is less than 25 acres ** Flathead National Forest Glaciers; GNP: Glacier National Park; FNF: Flathead National Forest ^For Blackfoot and Grinnell Glaciers, who’s masses retreated into separately named glaciers (Jackson and Salamander Glaciers, respectively) after the LIA, modern glacier names were maintained and intermediate moraines were used as approximation of LIA perimeter so the comparison of LIA area to modern area was possible. Content based on USGS ScienceBase data releases: Fagre, D.B., McKeon, L.A., Dick, K.A., and Fountain, A.G., 2017, Glacier margin time series (1966, 1998, 2005, 2015) of the named glaciers of Glacier National Park, MT, USA: U.S. Geological Survey data release, https://dx.doi.org/10.5066/F7P26WB1. Fagre, D.B., and Martin-Mikle, C.J., 2018, A comprehensive inventory of maximum glacial extent in Glacier National Park during the peak of the Little Ice Age: U.S. Geological Survey data release, https://doi.org/10.5066/P95YJ3CN.