Accelerated retreat of coastal glaciers in the Western Prince William Sound, Alaska

Figures & data

Table 1. General characteristics of study area glaciers

Region	GLIMS ID	Glacier name	Glacier type	Longitude (°)	Latitude (°)	Area (2018) (km^2)	Minimum elevation (m a.s.l.)	Maximum elevation (m a.s.l.)	Median elevation (m a.s.l.)
Chugach Mountains	G211267E61046N		Land-terminating	−148.73	61.05	11	594	1,524	1,041
	G211320E60963N		Land-terminating	−148.66	60.98	14	419	1,878	1,201
	G211348E60944N	Twentymile	Lake-terminating	−148.65	60.95	24	104	1,837	885
	G211353E61066N	Lake George	Lake-terminating	−148.65	61.06	84	143	2,164	1,049
	G211424E60880N	Billings	Land-terminating	−148.57	60.88	10	225	1,651	970
	G211481E60940N	Harriman	Tidewater	−148.53	60.94	50	6	1,808	709
	G211491E61046N	Surprise	Tidewater	−148.50	61.02	75	88	2,213	1,074
	G211615E61175N	Colony	Lake-terminating	−148.39	61.17	210	59	2,897	1,412
	G211805E61150N	Cascade	Tidewater	−148.19	61.16	15	192	2,456	1,463
	G211861E61338N	Knik	Lake-terminating	−148.14	61.34	412	32	3,631	1,743
	G211960E61143N	Coxe	Tidewater	−148.04	61.14	19	0	1,777	1,268
	G211952E61204N	Barry	Tidewater	−148.01	61.22	82	257	2,611	1,349
	G212501E61399N	Harvard	Tidewater	−147.64	61.32	450	0	4,010	1,776
	G212608E61223N	Meares	Tidewater	−147.39	61.23	115	4	2,541	1,449
	G212622E61302N	Yale	Tidewater	−147.34	61.32	129	364	3,599	2,168
Spencer–Blackstone Ice Complex	G211040E60441N		Land-terminating	−148.96	60.49	47	540	1,675	1,022
	G211075E60552N	Trail	Lake-terminating	−148.91	60.55	13	422	1,748	1,310
	G211088E60613N	Spencer	Lake-terminating	−148.87	60.63	74	67	1,810	898
	G211100E60420N	Wolverine	Land-terminating	−148.91	60.41	17	532	1,647	1,297
	G211128E60439N		Land-terminating	−148.87	60.44	17	226	1,654	1141
	G211194E60700N	Portage	Lake-terminating	−148.80	60.72	17	88	1,567	965
	G211241E60622N	Blackstone	Tidewater	−148.77	60.61	31	12	1,616	1,015
	G211244E60493N		Land-terminating	−148.73	60.55	14	245	1,737	910
	G211299E60617N	Beloit	Tidewater	−148.71	60.61	26	65	1,814	981
	G211320E60526N		Land-terminating	−148.68	60.55	12	351	1,824	952
	G211358E60580N	Taylor	Land-terminating	−148.66	60.58	12	95	1,766	934
	G211341E60606N	Cotterell	Land-terminating	−148.66	60.61	15	216	1,429	986
	G211468E60679N	Tebenkof	Land-terminating	−148.53	60.68	19	65	1,383	543
	G211232E60657N	Northland	Land-terminating	−148.77	60.66	21	109	1,377	735
Sargent Icefield	G211126E60158N	Ellsworth	Lake-terminating	−148.86	60.21	108	20	1,826	1,234
	G211143E60281N		Land-terminating	−148.85	60.29	18	540	1,565	1,277
	G211233E60341N		Land-terminating	−148.76	60.35	18	263	1,726	992
	G211266E60059N	Excelsior	Lake-terminating	−148.73	60.11	115	365	1,662	995
	G211299E60379N		Land-terminating	−148.70	60.38	12	223	1,591	985
	G211376E60282N	Chenega	Tidewater	−148.62	60.27	375	106	1,791	979
	G211386E60399N	Langdon	Land-terminating	−148.63	60.41	13	214	1,713	1,042
	G211420E60046N	Puget	Land-terminating	−148.58	60.07	13	415	1,391	1,012
	G211467E60175N	Tiger	Tidewater	−148.55	60.17	53	24	1,359	900
	G211493E60096N	Bainbridge	Land-terminating	−148.52	60.12	40	60	1,605	936
	G211561E60361N	Princeton	Land-terminating	−148.44	60.36	36	131	1,211	623
	G211617E60390N	Ultramarine	Lake-terminating	−148.38	60.39	16	157	797	525
	G211513E60431N	Nellie Juan	Tidewater	−148.49	60.43	41	226	1,383	657
	G211469E60427N	Falling	Land-terminating	−148.51	60.46	12	161	1,163	626

Note. Glaciers identified by glacier name (where available) and Global Land Ice Measurements from Space project identification numbers (GLIMS ID). Latitude and longitude represent glacier centroid. Elevation data based on 2018 outlines.

Table 2. Characteristics of study area weather stations

					Length of record
Weather station	Station identification	Altitude (m a.s.l.)	Longitude (°)	Latitude (°)	Temperature	Precipitation
Cannery Creek	USC00501240	25.9	−147.51	61.02	1979–2018	1979–2018
Cordova MK Smith Airport	USW00026410	9.4	−145.45	60.49	1950–2018	1950–2018
Seward Airport	USW00026438	6.7	−149.42	60.13	1950–2018	1950–2018
Wolverine Glacier	USGS15236895	990	−148.92	60.40	1967–2018	1967–2016

Table 3. Average annual retreat rates for the eight land-based study glaciers with estimated Little Ice Age maximum extents (LIAM date) based on tree-ring dating of moraines

		Length change rate
Glacier name	LIAM date	LIAM to 1950s (m a^−1)	1950s to 2018 (m a^−1)	1950s to 1973–1975 (m a^−1)	1973–1975 to 1986 (m a^−1)	1986 to 1994 (m a^−1)	1994 to 2006 (m a^−1)	2006 to 2018 (m a^−1)
Billings	1797	−9	−25	−64	−15	−1	−15	−8
Cotterell	1891	−25	−25	−17	−30	−33	−14	−35
Langdon	1737	−5	−11	−19	−4	−9	0	−10
Tebenkof	1891	−18	−25	−30	−11	−23	−13	−35
Wolverine	1713	−3	−18	−12	−8	−5	−9	−54
Ellsworth	1855	−12	−50	−44	−86	−20	13	−84
Excelsior	1797	−18	−135	−7	−119	−158	−168	−313
Ultramarine	1889	−17	−28	−9	−12	−34	−37	−65
Average		−14	−40	−25	−36	−35	−30	−76

Notes. Highlighted columns show average change rates before and after the 1950s.

Source. Wiles, Barclay, and Calkin (1999).

Figure 1. Study area and glacier area loss between the 1950s and 2018

Table 4. List of six derived topographic and geometric variables

Derived variable		Description	Data sources
Elevation mean		Average elevation of all DEM cells within the glacier outline.	ASTER GDEM
Aspect		Orientation of each DEM cell within a glacier outline as an azimuth (°) relative to 0° at due north	Randolph Glacier Inventory (based on imagery from 2006 to 2009; RGI Consortium 2017)
Slope		Average of slopes (°) of surfaces of each DEM cell within a glacier outline	Randolph Glacier Inventory (based on imagery from 2006 to 2009; RGI Consortium 2017)
Hypsometric interval		Difference between mean elevation and minimum elevation divided by relief (maximum elevation − minimum elevation) within the glacier outline (Pike and Wilson 1971; Y. Li and Li 2014)	ASTER GDEM
Shape index	Derived from $\sqrt{(4\pi \mathrm{x}A/P^2)}$, where A is the area and $P$ is the perimeter of a digitized glacier outline (Y. Li and Li 2014)		Landsat 7 ETM+ and Landsat 8 OLI/TIRS (July 2018)
Area (2018)		Glacier area based on digitized glacier outlines	Landsat 7 ETM+ and Landsat 8 OLI/TIRS (July 2018)

Note. GDEM = Global Digital Elevation Model; ETM+ = Enhanced Thematic Mapper Plus; OLI/TIR = Operational Land Imager/Thermal Infrared Sensor.

Table 5. Comparison of retreat rates and mean water depth for eight tidewater glaciers in the study area

Glacier	Time period	Rate of retreat (m a^−1)	Mean water depth (m)
Barry–Coxe	1898–1957	83	78
Beloit	1950–1975	3	13
Beloit	1975–1986	45	26
Blackstone	1975–1986	6	14
Coxe	1910–1957	43	90
Nellie Juan	1950–1975	46	28
Nellie Juan	1975–1986	50	42
Nellie Juan	1986–1994	57	48
Surprise	1898–1975	30	63
Tiger	1950–1973	16	53
Tiger	1994–2006	31	53
Yale	1810–1910	49	72
Yale	1910–1957	6	32
Yale	1957–1975	135	82
Yale	1975–1986	179	133
Yale	1986–1994	44	80
Yale	1994–2004	53	88

Table 6. Average length and area change metrics for land-based and tidewater glaciers

Metric		Glacier type	Unit	1950s to 1973–1975	1973–1975 to 1986	1986 to 1994	1994 to 2004–2006	2004–2006 to 2018
Length	Absolute change	Land-based	m	−451	−276	−199	−247	−601
		Tidewater	m	−175	−262	13	−172	−336
	Rate of change	Land-based	m a^−1	−20	−24	−25	−21	−48
		Tidewater	m a^−1	−8	−23	2	−15	−26
	Total cumulative change	Land-based	%	−4.2	−6.2	−7.7	−9.5	−14.1
		Tidewater	%	−0.6	−1.5	−1.4	−2.3	−4.3
Area	Absolute change	Land-based	km^2	−1.6	−1.1	−0.7	−1.4	−2.8
		Tidewater	km^2	−1.5	−2.0	−0.9	−1.2	−1.2
	Rate of change	Land-based	km^2 a^−1	−0.07	−0.09	−0.08	−0.12	−0.21
		Tidewater	km^2 a^−1	−0.08	−0.18	−0.11	−0.10	−0.09
	Total cumulative change	Land-based	%	−3.6	−6.2	−7.7	−11.3	−17.4
		Tidewater	%	−1.2	−2.5	−3.2	−4.6	−6.1

Table 7. Regression between glacier area change from 1950s to 2018 and six derived morphometric variables

	ΔArea
Explanatory variable	Estimate	p
Elevation mean	−0.01	.39
Aspect	−0.01	.51
Slope	0.60	.25
Hypsometric interval	51.96	.06
Shape index	−7.23	.53
Area	0.05	.03

Note. Bold value indicates significance at the 95 percent level (p < .05).

Table 8. Glacier mass (gigatons) and SLE changes from 1950–1957 to 2018

	n	Area (km^2)^a	Glacier mass change (Gt)		SLE rate (mm yr^−1)		SLE change (mm)
Measured glaciers	43	3,215	−63	±10	−0.003	±0.001	−0.174	±0.046
Unmeasured glaciers	2,827	4,651	−115	±18	−0.005	±0.001	−0.318	±0.084
Columbia Glacier	1	1,068	−201	±11	−0.009	±0.001	−0.555	±0.030
Total	2,871	8,934	−379	±38	−0.017	±0.003	−1.047	±0.160

Note. ^aArea refers to initial 1950–1957 estimates. SLE = sea level equivalent.

Figure 2. Percentage glacier length and area change since the 1950s. Vertical bars represent calculated uncertainty (one standard deviation)

Figure 3. (a) Average annual glacier retreat rates; (b) average annual glacier area change rates; and (c) total glacierized area annual change rates. Change rates presented by glacier type (land-based n = 30; tidewater n = 13)

Figure 4. Period area change rates (bars) and glacier area in 2018 (dashed line) for land-based glaciers

Figure 5. Length change rates for individual tidewater glaciers by time period

Figure 6. (a) Chronology of retreat for Nellie Juan Glacier between 1935 and 2018. Terminus position for 1935 from photographs in Field (1975; as cited in Wiles, Barclay, and Calkin 1999) and (b) chronology of retreat for Harvard and Yale glaciers between 1810 and 2018. Yale Glacier 1810 terminus position from Field and others (1958; as cited in Mercer 1961) and Harvard Glacier 1910 terminus position from Tarr and Martin (1914; as cited in Sturm et al. 1991)

Figure 7. Time series of (a) mean annual temperature at Cordova Airport station; (b) average winter temperature (PWS maritime stations); (c) mean summer temperature at Wolverine Glacier Station; and (d) average winter precipitation (PWS maritime stations). Dashed lines show statistically significant trends

Figure 8. Comparison between (a) annual summer (May–September) and winter (October–April) temperature and precipitation; (b) mean annual summer sea surface temperatures; (c) Pacific decadal oscillation (PDO); (d) Arctic Oscillation (AO); and (e) length change rates for land-based and tidewater glaciers

Figure 9. (a) Relationship between mean fjord water depth and retreat rates for tidewater glaciers and (b) comparison between tidewater glacier length and fjord width changes from 2004–2006 to 2018. Note, measurements based on early August 2004–2006 and late July 2018 imagery

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