8, 305–308. The glaciers are now in disequilibrium with the already realized warming (Christian et al., 2018), because of their several-decades-long response times (Jóhannesson et al., 1989; Harrison et al., 2001), and would continue to lose mass even if temperatures could be stabilized in the near future. An aerial view of 80 years of climate-related glacier fluctuations in southeast Greenland. Front. “Geographic names of Iceland’s glaciers,” in Historic and modern (Washington: U.S. Geological Survey Professional Paper), 1746. Dynamic simulations of Vatnajökull ice cap from 1980 to 2300. A systematic, regional assessment of High Mountain Asia glacier mass balance. Calving, or the breaking off of icebergs from glaciers, has increased at many glaciers along the west coast of Svalbard. 1 Introduction. Grennan Milliken 30 October 2019. Climate change 2013: the physical science basis. I had already been to Portage three times in the last week. Our results emphasize the importance of direct observations from glaciers located in Iceland for evaluation of global glacier variations. It is genuinely astonishing – the volume of the collapse is apparently 7.4 cubic kilometres. Res. Commun. The 1890* and 1890** for Vatnajökull show the volume estimates with the reduced area to compensate for the large portion of surging outlets from Vatnajökull (see main text). Received: 30 December 2019; Accepted: 13 October 2020;Published: 26 November 2020. Changes in the southeast Vatnajökull ice cap, Iceland, between ∼1890 and 2010. A part of this non-surface mass balance is caused by calving activity, which was insignificant in the first half of the 20th century, but has been gradually increasing with the ongoing retreat of the outlet glaciers located in over-deepened troughs (Guðmundsson et al., 2019). 43, 12138–12145. (2020), is non-negligible, accounting for about one-fifth of the mass loss since 1994. doi:10.1093/gji/ggx008, Tedesco, M., and Fettweis, X. The area loss since the end of the Little Ice Age (LIA) is ∼2,200 km2 and ∼750 km2 since the year 2000, or about 40 km2 (or 0.4%) per year (Hannesdóttir et al., 2020). J. Glaciol. Ann. Atmosphere 9, 450. doi:10.3390/atmos9110450, Schuler, T. V., Kohler, J., Elagina, N., Hagen, J. O. M., Hodson, A. J., Jania, J. J. Glaciol. Sigurðsson, O., Williams, R. S., and Víkingsson, S. (2017). The more unrealistic assumption of full dependence between uncertainties, which would yield a direct sum of the uncertainties instead, would result in only ∼25% higher uncertainties. Glaciol. Rep., ví 2017-016. Calving glaciers, which discharge icebergs into an ocean or lake, have retreated more rapidly than those on land because of sections collapsing at the glacier front and due to submarine melting. Further investigation of the rate and modes of crevasse propagation could integrate linear elastic fracture … There are strong similarities in the response of glaciers around the North Atlantic Ocean to atmospheric conditions, in particular at a multi-decadal time scale. Two of us skated, while the oth… As discussed above, annual mass-balance data are not available prior to 1980/81, so we have used geodetic observations and the volume–area scaling to extend the record to the end of the 19th century. doi:10.1016/j.gloplacha.2014.09.003, Gascoin, S., Guðmundsson, S., Aðalgeirsdóttir, G., Pálsson, F., Schmidt, L., Berthier, E., et al. First, Vatnajökull did not at any one time reach the determined maximum LIA extent because the surges responsible for the geomorphological evidence of maximum extent did not occur simultaneously. For the periods without observations, we assume a calving rate that changes linearly from 0 in 1950/51 [start of significant calving (Björnsson et al., 2001)] to −0.029 m w.e. doi:10.5194/tc-11-191-2017. (2016). Glacier mass loss is a global phenomenon, and the rates in the early 21st century are unprecedented for the observed period (Zemp et al., 2015). doi:10.5194/tc-6-1295-2012, Marzeion, B., Leclercq, P. W., Cogley, J. G., and Jarosch, A. H. (2015). The calving event lasted for 75 minutes and the glacier retreated a full mile across a calving face three miles wide. (2) Simulation of the surface mass balance of Vatnajökull for the years 1980/81 to 1991/92 from the HIRHAM5 snowpack model that uses MODIS albedo (Schmidt et al., 2017) and is forced with a ERA-Interim downscaling using the HARMONIE–AROME model at 2.5 km resolution (Schmidt et al., 2019) (see shaded area in Figure 3A). Mass loss by calving contributes significantly to the uncertainty of sea-level rise projections. (2020) from −0.075 m w.e. 97, 237–264. The corresponding minimum and maximum volume estimates for Vatnajökull in 1945 and 1890 (shown with error bars in Figure 4) are larger than the volumes estimated for the LIA maximum area (1890 star in Figure 4) and the doubled area correction due to surges (1890** star in Figure 4). J. Geophys. 2nd Edn. The calving will continue to increase as the glaciers retreat, and should, along with other non-surface mass-balance components, be taken … 8:574754. doi: 10.3389/feart.2020.523646. doi:10.1080/20014422.1940.11880686, Thorarinsson, S. (1943). Glaciers in Iceland have received much attention through the centuries due to their proximity to inhabited regions (Figure 1). Present glacier shrinkage, and eustatic changes of sea-level. 40, 495–502. Oscillations of the Iceland glaciers in the last 250 years. JB, EM, EB, and TJ processed and contributed the geodetic estimates. With less snowfall on the glaciers, dirty ice appears earlier from beneath the snow in spring, which enhances the glacier ablation (Björnsson et al., 2013; Gunnarsson et al., 2020). J. Geosci. glacier models is unable to adequately resolve this critical interaction between ice sheets and climate. Change. Nature 579, 233–239. Nat. 2020, 1–32. (2017) showed that signal leakage due to mass changes of the neighboring Greenland Ice Sheet and the effect of glacial isostatic rebound need to be carefully taken into account. Several glaciers had, during their retreat, split into two or more separate glaciers or ice patches. Sigurðsson, O. Glaciers in most areas of the world are losing mass as global temperatures rise in response to increased greenhouse gas concentrations in the atmosphere (e.g., Vaughan et al., 2013; Hock et al., 2019; Meredith et al., 2019; Zemp et al., 2019). A single value of 0.10 m w.e. (2020). During the relatively warm period 1930/31–1949/50, mass loss rates were probably close to those observed since 1994, and in the colder period 1980/81–1993/94, the glaciers gained mass at a rate of 1.5 ± 1.0 Gt a−1. (2020) and volumes are calculated in this study], and Mýrdalsjökull [∼598 km2, ∼140 km3, in the year 1991 (Björnsson et al., 2000)], near the southern coast. The physical basis of glacier volume–area scaling. We went kayaking in the glacier bay in our Intex K2 Explorer kayaks and witnessed a MASSIVE event as a chunk of a glacier calved about 50 foot from us and created a 10-12 foot wave. Calving, or the breaking off of icebergs from glaciers, has increased at many glaciers along the west coast of Svalbard. FIGURE 5. Jökull 69, 1–34. The above records were combined to calculate the mass balance of all Icelandic glaciers from 1890/91 to 2018/19. Surface and bedrock topography of the Mýrdalsjökull ice cap, Iceland: the Katla caldera, eruption sites and routes of jökulhlaups. Rev. Res. 110, F02011. 47, GL087291. Cryosphere 10, 159–177. Insulation effects of Icelandic dust and volcanic ash on snow and ice. Mean specific surface mass-balance records of the three largest glaciers in Iceland obtained with glaciological method (in situ surveys). The surface mass-balance record obtained with the glaciological method for Langjökull (in 1997/98–2003/04) has been compared with volume changes derived from geodetic mass-balance estimates (Pálsson et al., 2012). a−1 for the long periods obtained with volume–area scaling is supported by Figure 4. Date of experience: August 2019. Volcanol. ICES (2018). The volume of a glacier can be obtained by integrating the ice thickness, calculated as the difference between surface and bedrock DEMs. "CHASING ICE" captures largest glacier calving ever filmed - … send. Annual glaciological mass-balance measurements started on Hofsjökull in the glaciological year 1987/88 (Thorsteinsson et al., 2017), in 1991/92 on Vatnajökull, and 1996/97 on Langjökull (Björnsson et al., 1998; Björnsson et al., 2002). A., Kjær, K. H., Korsgaard, N. J., Khan, S. A., Kjeldsen, K. K., Andresen, C. S., et al. The volume–area point marked 1890* for Vatnajökull in Figure 4 includes an area correction that corresponds to a 500 m retreat (area reduction by 100 km2), and the point marked 1890** includes double this area correction (the point marked 1890 corresponds to data that have not been adjusted to reflect the impact of the surges on the area). The glaciological observations started on Hofsjökull in 1987/88 and annual variabilty in the period 1980/81 to 1987/88 is obtained from simulations from the HIRHAM5 snowpack model (Schmidt et al., 2019, see the Section 2). 36, 82–90. a−1, respectively. (2019). All recent studies and measurements with various methods are compiled and combined; a new estimate of the ∼1890 volumes of the three largest ice caps is made using new data on their area at that time (Hannesdóttir et al., 2020) and volume–area scaling (Bahr et al., 2015), and the recently established non-surface mass balance of Icelandic glaciers, that takes into account energy dissipation caused by the flow of water and ice, geothermal melting, volcanic eruptions, and calving (Jóhannesson et al., 2020), is included to improve the estimate of the mass-balance history of all glaciers in Iceland since the end of the LIA. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). doi:10.5194/tc-2019-328, Hannesdóttir, H., Björnsson, H., Pálsson, F., Aðalgeirsdóttir, G., and Guðmundsson, S. (2015a). doi:10.3189/S026030550000104X. 8, 11–18. (2020). Cryosphere 11, 1665–1684. The contribution of other glaciers is from geodetic results (Belart et al., 2020), including an estimated annual variability (see Section 2). Res. A spatially resolved estimate of High Mountain Asia glacier mass balances from 2000 to 2016. a−1. Limited influence of climate change mitigation on short-term glacier mass loss. Earth Sci. 9 (5), 399. doi:10.3390/rs9050399, Geirsdóttir, Á., Miller, G. H., Axford, Y., and Ólafsdóttir, S. (2009). The time steps in this study correspond to the glaciological year (Cogley et al., 2011) from autumn to autumn, using the floating-date mass-balance system (Østrem and Brugman, 1991; Björnsson et al., 2002; Cogley et al., 2011), that is, the end of the summer melt season marks the start of a new glaciological year. This work and collection of data on which this work is based has been supported financially by and with the participation of the University of Iceland Research Fund; the National Power Company of Iceland; the Icelandic Public Road Administration; Iceland Glaciological Society; Reykjavík Energy Environmental and Energy Research Fund; three multinational European Union research projects TEMBA, ICEMASS, and SPICE; two projects supported by Nordic Energy Research: Climate and Energy (CE) and Climate and Energy Systems (CES); the Nordic Centre of Excellence SVALI (Stability and Variations of Arctic Land Ice), funded by the Nordic Top-level Research Initiative (TRI); and the Icelandic Ministry for the Environment and Natural Resources through the cooperative project Melting glaciers. doi:10.1017/jog.2020.37, Jóhannesson, T., Raymond, C., and Waddington, E. (1989). In 2014/15, high winter precipitation and reduced melt during a short and cold summer caused a single anomalous year with positive mass balance. The geodetic mass balance of Eyjafjallajökull ice cap for 1945–2014: processing guidelines and relation to climate. doi:10.1080/20014422.1943.11880716, Thorsteinsson, T., Jóhannesson, T., and Snorrason, Á. Global glacier mass loss during the GRACE satellite mission (2002–2016). Velicogna, I., Mohajerani, Y., Geruo, A., Landerer, F., Mouginot, J., Noel, B., et al. (2020) of 0.055 m w.e. Figure 3F shows that the cumulative mass change is primarily from Vatnajökull (365 ± 115 Gt) and that Langjökull and Hofsjökull have lost 63 ± 17 and 51 ± 13 Gt, respectively. doi:10.5194/tc-5-961-2011, Ágústsson, H., Hannesdóttir, H., Thorsteinsson, T., Pálsson, F., and Oddsson, B. [Above: Jason Rouch Jr. made this video of ice calving at Portage Glacier on Saturday, April 11, 2020.] A glacial calving in southeast Iceland caused a sudden large wave that sent observing tourists scrambling for cover, and the event was captured on video. 63, 95–140. doi:10.1017/aog.2020.10. Surface elevation change and mass balance of Icelandic ice caps derived from swath mode CryoSat-2 altimetry. Zemp, M., Huss, M., Eckert, N., Thibert, E., Paul, F., Nussbaumer, S. U., et al. 122, 330–344. Have any problems using the site? doi:10.1029/2004JF000200, Foresta, L., Gourmelen, N., Pálsson, F., Nienow, P., Björnsson, H., and Shepherd, A. Jökulsárlón at Breiðamerkursandur, Vatnajökull, Iceland: 20th century changes and future outlook. 7, 96. doi:10.3389/feart.2019.00096. doi:10.3189/172756403781816365, Brun, F., Berthier, E., Wagnon, P., Kääb, A., and Treichler, D. (2017). : 4. glacier mass-balance measurements: a Manual for Field and Office work. website: www.homewiththehoopers.cominstagram: https://www.instagram.com/homewiththehoopers/FB: https://www.facebook.com/homewiththehoopers/?ref=bookmarksSteeringSouth (Josh Bastyr): https://www.youtube.com/channel/UCcz3eUxIXrnHSPmIAQRWc7wJukin Media Verified (original)For licensing/permission to use: Contact - email@example.com The cooler oceanic conditions after 2010 (ICES, 2018) cooled the atmosphere and thereby reduced the mass loss in Iceland and Norway, and in Greenland the mass loss slowed down after a record mass-loss year in 2012 (Shepherd et al., 2019; Velicogna et al., 2020). Zemp et al. Earth Sci. (2018). Earth Environ. Geogr. Reconstructions of glacier mass-change rates for the 20th century and the first decade of the 21st century show substantial temporal and spatial variations, but a global mass loss trend became clear toward the end of the 20th century (Leclercq et al., 2011; Marzeion et al., 2015; Marzeion et al., 2012). With more detailed information about the past mass changes of Icelandic glaciers, models for projecting their future evolution can be improved. doi:10.1016/j.quascirev.2009.03.013, Guðmundsson, M. T., Sigmundsson, F., Björnsson, H., and Högnadóttir, Þ. Glaciers in Iceland are all temperate and cover about 10% of the area of the country (Björnsson and Pálsson, 2008), with the largest ice cap Vatnajökull (∼7,700 km2, ∼2,870 km3, in the year 2019) located near the southeast coast, two smaller ice caps Langjökull (∼835 km2, ∼171 km3, in the year 2019) and Hofsjökull (∼810 km2, ∼170 km3, in the year 2019) in the central highlands [area estimates are from Hannesdóttir et al. In some years, the spring is cool, so glacier ice appears later from beneath the snow. Surv. Reviewed November 5, 2019 via mobile . Rem. The rate in the rapid downwasting period 1994/95–2018/19 is −9.6 ± 0.8 Gt a−1. a−1, respectively, during the period of glaciological observations on each glacier (see Figure 2). Mass balance of western and northern Vatnajökull, Iceland, 1991–1995. ScienceDaily, 8 May 2019. The uncertainty of 0.1 m w.e. Cryosphere 14, 1043–1050. Bedrock DEMs for the three largest ice caps have been made from dense radio-echo sounding data (Björnsson and Pálsson, 2020) and are assumed stable over time. doi:10.1029/2004JF000262, Marzeion, B., Jarosch, A. H., and Hofer, M. (2012). Evolution of the Norwegian plateau icefield Hardangerjøkulen since the “little ice age”. Since 2010, the mass loss rate has on average been ∼50% lower, with the exception of 2018/19, when one of the highest annual mass losses was observed (mass change rate −15.0 ± 1.6 Gt a−1). doi:10.5194/tc-9-565-2015, Hannesdóttir, H., Björnsson, H., Pálsson, F., Aðalgeirsdóttir, G., and Guðmundsson, S. (2015b). (2020) for the years 1996/97–2016/17, resulting in an average of −0.056 m w.e. Paris, France: UNESCO–IHP, 114. On those timescales, this study does not clearly indicate periods of substantially positive mass balance. Conditions were borderline legendary. Long-term and inter-annual mass changes in the Iceland ice cap determined from GRACE gravity using Slepian functions. 28, 2107–2118. 22, 131–159. Alaskan Glacier Calving Columbia With Epic 200 Foot High “Shooter” After 1995, we have detailed glaciological observations, made on ∼60 survey sites on Vatnajökull and ∼25 survey sites on each of Hofsjökull and Langjökull, which show mass loss every year until 2014. Glaciol. The GRACE record (Wouters et al., 2019) has some years (e.g., 2006/07 and 2010/11) with more negative mass change, and others (e.g., 2005/06, 2011/12, and 2013/14) are less negative than our estimates, although the data points from our record are within the large uncertainty range of the GRACE values. Below we discuss i) how the surface mass balance from the glaciological method is combined with the non-surface mass-balance estimates, ii) the application of the volume–area scaling to estimate past volumes of the three largest ice caps, and iii) the uncertainty of the obtained total mass balance of the Icelandic glaciers. The choice of the year 1890 as the time of maximum LIA extent of glaciers in Iceland for our analysis leads to some uncertainty in the mass-balance estimate for the first period after 1890, as the glaciers in fact reached the LIA maximum extent at different times. (2020). Variations of Iceland glaciers 1931–1960. a−1 for Vatnajökull and 0.07 m w.e. When calculating the uncertainty of the mass change of all Icelandic glaciers for the four IPCC periods (shown as horizontal lines in Figure 5), the uncertainties of the different contributions are considered independent. Figure 4). sms.
On the characterization of glacier response by a single time-scale. Front. The effect of surges on Hofsjökull and Langjökull is much smaller than on Vatnajökull and therefore not taken into account in this study. The annual variability is large: for the Vatnajökull record, the standard deviation of the observations is 0.75 m w.e. Left: The specific mass balance of glaciers in Iceland as observed, modeled, and estimated with various methods. Footage captured using GoPro Hero 7 Black. The 1996 eruption at Gjálp, Vatnajökull ice cap, Iceland: course of events, efficiency of heat tranfer, ice deformation and subglacial water pressure. doi:10.5194/tc-10-159-2016, Marshall, S. J., Björnsson, H., Flowers, G. E., and Clarke, G. K. C. (2005). It is unfortunate that the more recent DEM [from 2004 used in Pálsson et al. Radio-echo sounding on the temperate ice caps in Iceland required a much longer electromagnetic wavelength than had been used on the cold polar ice caps (Björnsson and Pálsson, 2020). 8, 156. doi:10.3389/feart.2020.00156, Shean, D. E., Bhushan, S., Montesano, P., Rounce, D. R., Arendt, A., and Osmanoglu, B. doi:10.1029/2012JF002523. Mass and volume changes of Langjökull ice cap, Iceland, ∼1890 to 2009, deduced from old maps, satellite images and in situ mass balance measurements. Glacier change in Norway since the 1960s—an overview of mass balance, area, length and surface elevation changes. Data from automatic weather stations and glaciological surface mass balance, and runoff measurements were used to constrain the model (Schmidt et al., 2018). (2015). (2017) reported that glacier geometries that did not result in calving in Elmer/Ice via crevasse depth calving laws still produced large full-depth calving event when exported into HiDEM, a model representing glacier ice as a lattice of particles connected by breakable elastic beams. Björnsson, H., Pálsson, F., and Guðmundsson, S. (2001). Master’s thesis. Impact Factor 2.689 | CiteScore 3.3More on impact ›, Observational Assessments of Glacier Mass Changes at Regional and Global Level
a−1 and −0.067 m w.e. Unmeasured glaciers (Ou) corresponded to ∼1.3% of the total area in 2019 (Hannesdóttir et al., 2020). Each method may have a constant bias, of a similar magnitude to the estimated uncertainties; the probability of the minimum mass change occurring for all periods (or alternatively maximum mass change for all periods) is, however, smaller. (2020). The two pronounced extremes in 1996/97 and 2009/10 show the melting of ∼3.7 Gt of ice due to the Gjálp eruption (mid-Vatnajökull) in October 1996 and the enhanced melting in summer 2010 caused by the deposition of a thin layer of volcanic tephra on the ice cap surfaces during the Eyjafjallajökull eruption in April–May 2010. It is a form of ice ablation or ice disruption.It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse.The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway. Howard Ulrich, a fisherman visiting Lituya Bay with his 8-years-old son that day, at first heard a loud rumbling noise from up at the head of the … Mernild, S. H., Lipscomb, W. H., Bahr, D. B., Radić, V., and Zemp, M. (2013). It is not straightforward to estimate the uncertainty of the mass-balance estimates derived from the different observations and methods described above. Cryosphere 14, 1209–1223. A comparison of our results to the annual mass change rates of Zemp et al. Modelling the 20th and 21st century evolution of Hoffellsjökull glacier, SE-Vatnajökull, Iceland. The area of the glaciers in ∼1890 is based on geomorphological evidence of the maximum LIA extent in Iceland (Hannesdóttir et al., 2020). ICES report on ocean climate. Buoyant forces promote tidewater glacier iceberg calving through large basal stress concentrations Matt Trevers1, Antony J. Payne1, Stephen L . Report No. J. Glaciol. The larger ice cap Vatnajökull will survive longer; it is projected to lose 20–30% of its mass until the end of the century. a−1 and for Langjökull and Hofsjökull 0.85 m w.e. (2017). Non-surface mass balance of glaciers in Iceland. Our study thus shows that Scandinavian glaciers are not representative of glacier mass change in Iceland. Retreat of calving glaciers worldwide has contributed substantially to sea-level rise in recent decades. (Editors) (2020a). Treating the methods as independent would therefore lead to underestimation of the uncertainties. Mass change records for Icelandic glaciers have been made from the glaciological observations provided to the World Glacier Monitoring Service (WGMS) database (Zemp et al., 2019) (a subset of the observations presented in Figure 3), from ICESat data (Nilsson et al., 2015) (−10 ± 3 Gt a−1 for 2003–2009), CryoSat2 data (Foresta et al., 2016) (−5.8 ± 0.7 Gt a−1 for October 2010–September 2015), and the GRACE observations (von Hippel and Harig, 2019; Wouters et al., 2019; Ciracì et al., 2020). Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data – case study from Drangajökull ice cap, NW Iceland. Regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data. Geogr. The animation at the top of this page shows a wide view of Pine Island Glacier (PIG) and the long-term retreat of its ice front. Almost half of the total mass loss has occurred since 1994/95 (240 ± 20 Gt, corresponding to 9.6 ± 0.8 Gt a−1 on average). The cumulative mass change of all the glaciers for each period was computed as the sum of the total mass balance of the all glaciers (the product of the specific mass balance and the time-dependent glacier area). Front. Cryosphere 7, 877–887. a−1 for Vatnajökull, which is responsible for most of the 1.5 ± 1.0 Gt a−1 mass gain of Icelandic glaciers during that period. Nat. They have each grown to 20km in length and could shear off a hunk of ice the size of Paris and Manhattan combined. Zemp, M., Frey, H., Gärtner-Roer, I., Nussbaumer, S. U., Hoelzle, M., Paul, F., et al. Ann. [in (G) the mass change of Mýrdalsjökull for the years 1945/46–1959/60, not included in (Belart et al., 2020), is estimated from a linear fit (with R2=0.98) between the mass balance of Mýrdalsjökull and the average mass balance of the neighboring glaciers, Eyjafjallajökull, Torfajökull, and Tindfjallajökull, during the other five periods shown in (D)]. Shocking huge Glacier calving creates huge wave like tsunami … Measurements by Institute of Earth Sciences, University of Iceland, and the National Power Company of Iceland (Langjökull and Vatnajökull) and the Icelandic Meteorological Office (Hofsjökull). These values are supposed to reflect the uncertainty of the average mass-balance rate over a decade or longer period. (7) Estimates of the volumes of Vatnajökull and Hofsjökull in 1890 and 1945 as well as the volume of Langjökull in 1890 based on the volume–area scaling (Bahr et al., 1997; Bahr et al., 2015) (Figure 4). Reykjavík, Iceland: Icelandic Meteorological Office, 84. Nat. Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. Here, we see tourists visiting Jökulsárlón, with the glacier Breiðamerkurjökull in the background. Sensitivity of Vatnajökull ice cap hydrology and dynamics to climate warming over the next 2 centuries. Timescales for redistribution of ice volume to maintain the characteristic shape of a glacier are expected to be much shorter than the response time of the glacier to mass-balance changes (Jóhannesson et al., 1989; Harrison et al., 2001). To construct the mass-balance history of Icelandic glaciers back to the year 1890/91 [assumed here to be the end of the LIA in Iceland (Thorarinsson, 1943; Sigurðsson, 2005)], we compile and combine different data sets and methods. The gray area in (A) indicates a period of modeled surface mass balance for Vatnajökull (Schmidt et al., 2019), green boxes in (A) and (C) are estimates from various sources (see main text), red boxes in (B) and lines in (D) are from geodetic mass balance (Pálsson et al., 2012; Belart et al., 2020) (heights of the boxes indicate uncertainty of measurements), and purple boxes in (A), (B), and (C) show estimated mass loss from volume–area scaling method (see. An underwater pressure sensor capable of making 20 measurements per second was placed in front of the glacier to record calving-generated tsunami waves measuring 10 centimeters to 1 meter high. In the period 1890–2019, Vatnajökull, Langjökull, and Hofsjökull lost 12 ± 4, 29 ± 8, and 25 ± 6%, respectively, relative to their estimated mass in 1890. The projected mass losses toward the end of the 21st century are more rapid and persistent than the observations presented here. a−1 and 0.78 m w.e. The non-surface mass balance of glaciers in Iceland, as estimated by Jóhannesson et al. (2020), is assumed constant for the whole period: −0.085 m w.e. For individual years, the uncertainty is assumed to be double this value, due to errors changing randomly from year to year. (2020). Gunnarsson, A., Gardarsson, S. M., Pálsson, F., Jóhannesson, T., and Sveinsson, O. G. B. tweet. Björnsson, H., Pálsson, F., and Guðmundsson, M. T. (2000). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. We therefore consider the uncertainties of the specific mass balance for the period of volume–area scaling as a generous estimate. and 56 m w.e, respectively. There is, however, a large variability in the melting due to several factors. 125, e2019jf005357. Geophys. Jökull 45, 35–38. Glacier calving is a majestic and sad sight. Holocene 29, 1885–1905. Talence, France: Bordeaux INP ENSEGID. Similarities and differences in the response of two ice caps in Iceland to climate warming. The previously estimated mass change rate of −9.5 ± 1.5 Gt a−1 for the period 1994/95–2009/10 (Björnsson et al., 2013), which included 0.5 Gt a−1 from geothermal melting (∼3% of typical ablation of the survey period), is less negative than the current estimate for the same period: −11.6 ± 0.8 Gt a−1, now including the recent improved estimate of the contribution from other glaciers than the three largest, the non-surface melt, and calving in Jökulsárlón. doi:10.1029/2005JF000388, Aðalgeirsdóttir, G., Guðmundsson, S., Björnsson, H., Pálsson, F., Jóhannesson, T., Hannesdóttir, H., et al. Reykjavík, Veðurstofa Íslands: National Energy Authority, 6. For a similar approach used at Perito Moreno glacier, Patagonia, calving sizes were es-timated from calving areas visible on time … Sci. The uncertainty of the total mass change for 1970/71 to 2017/18, 1992/93 to 2017/18, and 2005/06 to 2017/18 is therefore, For 1900/01 to 1989/90, the total uncertainty is. Environ. 47, GL086926. |, U.S. Geological Survey Professional Paper, CSU(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, https://doi.org/10.3389/feart.2020.523646, https://www.frontiersin.org/articles/10.3389/feart.2020.523646/full#supplementary-material, https://www.ipcc.ch/srocc/chapter/chapter-2/, https://www.ipcc.ch/srocc/chapter/chapter-3-2/, https://wgms.ch/downloads/Oestrem_Brugman_GlacierMassBalanceMeasurements_1991.pdf. The determined values for mean specific mass balance for two periods for Hofsjökull and Vatnajökull (1890/91 to 1944/45 and 1945/46 to 1969/70) and one period for Langjökull (1890/91 to 1936/37) are shown with purple lines in Figures 3A,B,C. The previously published mass-balance record for the Icelandic glaciers has now been revised by including this component. scale 1:500,000, with two inset maps of 1:250,000, Tröllaskagi and Kerlingarfjöll, with accompanying illustrated pamphlet, and list of glacier place-names. a−1 for Hofsjökull and Langjökull, during the periods of observed/modeled surface mass balance and for the mean values obtained with volume–area scaling (see below for a justification of these values). doi:10.5194/tc-11-1665-2017, Schmidt, L. S., Aðalgeirsdóttir, G., Pálsson, F., Langen, P. L., Guðmundsson, S., and Björnsson, H. (2019). J. Geophys. The obtained mass change rate for the period 1950–1990 in their record is about double the rate that we find here (−4.0 vs. −1.7 Gt a−1). Zurich, Switzerland: CSU(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, 274. Clim. A part of this non-surface mass balance is caused by calving activity, which was insignificant in the first half of the 20th century, but has been gradually increasing with the ongoing retreat of the outlet glaciers located in over-deepened troughs (Guðmundsson et al., 2019). Res. Global glacier changes: a revised assessment of committed mass losses and sampling uncertainties. IPCC special report on the ocean and cryosphere in a changing climate. Remote Sens. The mass balance year 2014/15 was characterized by a long sequence of low-pressure systems arriving one after another through the winter, bringing large amounts of precipitation, followed by a cool summer with little melt, resulting in positive mass balance on all the glaciers. (2012)] was obtained in mid-August so the surface melting until the end of the melt season (late September) was not accounted for. Using volume–area scaling to estimate changes in the volume of glaciers with a well-known subglacial topography, from variations in glacier area over decadal time spans, may be expected to be more accurate because this mainly relies on the assumption that the glacier maintains a similar shape as it responds to mass-balance variations with changes in its area and volume. For other periods of this study, the glaciers were either close to equilibrium or experienced mild loss rates. When calculating the uncertainty of each time series shown in Figure 3G, the uncertainty for each contribution ΔCV, ΔCL, ΔCH, and ΔCO (corresponding to Vatnajökull, Langjökull, Hofsjökull, and “others”, respectively) is derived by cumulating the assigned annual uncertainties. doi:10.1038/s41586-019-1855-2. Res. Jökull 63, 91–104, Andreassen, L. M., Elvehøy, H., Kjøllmoen, B., and Belart, J. M. C. (2020). The most rapid loss is observed in the period 1994/95 to 2009/10 (mass change rate −11.6 ± 0.8 Gt a−1). This corresponds to uncertainty values typically given for 10–20 year periods (Belart et al., 2020), while for periods exceeding 30 years, the uncertainty estimates are typically on the order of a few cm w.e. (2017). The geodetic mass balance estimates from Belart et al. Thorsteinsson, T., Jóhannesson, T., Sigurðsson, O., and Einarsson, B. For other periods of the study, the glaciers were either close to equilibrium or experiencing mild loss rates. The results for the three ice caps for dates of observed areas and corresponding glacier volumes are shown with filled circles on the volume–area scatter plot in Figure 4. Ann. Lett. (2018). Glaciol. Icelandic glaciers. The results of von Hippel and Harig (2019) are not corrected for isostatic rebound and the mass loss rate of Ciracì et al. They neither reflect random annual errors in those records, nor annual deviation from long-term means for the geodetic and volume–area scaling results. The 1890 values are obtained using area based on geomorphological evidence of the Little Ice Age maximum extent (Hannesdóttir et al., 2020). doi:10.5194/tc-11-741-2017, Wouters, B., Gardner, A. S., and Moholdt, G. (2019). 233, 111396. doi:10.1016/j.rse.2019.111396, Möller, R., Möller, M., Kukla, P. A., and Schneider, C. (2016). The mass changes of all glaciers in Iceland as estimated from the data presented in Figure 3, showing annual values for the period 1980/81 to 2018/19 and average mass loss rates for the five periods; 1890/91–2018/19 (black), 1900/01–1989/90 (red), 1970/71–2017/18 (orange), 1992/93–2017/18 (green), and 2005/06–2017/18 (blue). This approach has its limitations for surge-type glaciers but may be expected to provide reasonable volume-change estimates over long time periods with substantial changes in volume, even for ice caps with many outlet glaciers that may surge at irregular intervals. Cryosphere 5, 961–975. Jökull 62, 81–96. We note that over the time periods considered in this article, repeated surface mapping and surface reconstructions of the glaciers, where available, have shown elevation changes that are small in the interior of the glacier and amplified toward the ice margin, as expected if the glacier maintains a geometrically similar shape as it adjusts toward a new geometry during variations in the climate (Hannesdóttir et al., 2015b; Thorsteinsson et al., 2017). Average mass change rates are computed for several selected periods (the reporting periods of the forthcoming IPCC AR6 assessment; see colored horizontal lines in Figure 5): 1900/01–1989/90: −3.1 ± 1.1 Gt a−1, 1970/71–2017/18: −4.3 ± 1.0 Gt a−1, 1992/93–2017/18: −8.3 ± 0.8 Gt a−1, and 2005/06–2017/18: −7.6 ± 0.8 Gt a−1. Ice-volume estimates at other times can be calculated by multiplying the annual specific mass balance (Figure 3) of each glacier by the corresponding glacier area, linearly interpolated with time between dates of area observations, converting the annual mass change into ice volume [assuming the conversion factor 0.85 (Huss, 2013); note that mass-balance records previously published that used conversion factor 0.9 (Pálsson et al., 2012; Jóhannesson et al., 2013) have been adjusted accordingly (Thorsteinsson et al., 2017)] and integrating the volume change relative to the date of the surface DEMs listed above. Remote Sens. doi:10.5194/tc-9-2399-2015, Marzeion, B., Kaser, G., and Maussion, F. (2018). high mountain areas. doi:10.3189/172756501781831837. This was shot on August 10th at Spencer … 11 April 2019 Many people are familiar with ocean tsunamis caused by earthquakes, such as the devastating Japan 2011 tsunami, but fewer know they can also be caused by iceberg calving. We present results from a new approach combining the continuum model Elmer/Ice and the discrete element/particle model HiDEM, applied to Store Glacier, a large calving glacier in West Greenland. : Earth Surface. Earth Surface. FIGURE 4. Jökull 50, 1–18. Meredith, M., Sommerkorn, M., Cassotta, S., Derksen, C., Ekaykin, A., Hollowed, A., et al. Evaluation of MODIS albedo product over ice caps in Iceland and impact of volcanic eruptions on their albedo. Earth Sci. This specific mass-balance uncertainty results in volume uncertainty of 127 km3 and 72 km3 for the Vatnajökull volumes in 1890 and 1945, respectively, when the uncertainties are cumulated from the date of the surface DEM (autumn 2010) used to calculate the volume (see Section 2.2). (2020b). Ask kennethj133 about Mendenhall Glacier Visitor Center. To take this into account, we reduced the area so it represents the likely ice-cap area when the surge-type outlets are on average near their mid-quiescent-period size. Jökull 51, 75–78. The terminus locations are also noted by red dots for … Second, right after a surge, the glacier spreads over a larger area than before without any increase in volume, resulting in a thinner glacier with smaller volume than indicated by the volume–area relationship (Eq. Volume–area scaling has been widely used to estimate the volume of glaciers with an unknown subglacial topography/ice thickness (e.g., Radić and Hock, 2010), and changes in ice volume associated with variations in glacier extent when multi-temporal DEMs of the glacier surface are not available (e.g., Pálsson et al., 2012). Cumulating the specific mass-balance values for this period (Figure 3F) shows that Vatnajökull has lost about 45 m w.e. The sound of ice cracking was faint at first. These measurements, together with the HIRHAM5 snowpack model simulations, yield a detailed record of the winter, summer, and annual surface mass balance during the last three to four decades for these ice caps (Figure 2), constituting ∼90% of the glacier area in Iceland. Their volumes have been calculated using the following surface DEMs: lidar surface DEM of Hofsjökull from 2008 (Jóhannesson et al., 2013), a SPOT5-HRS (Korona et al., 2009) surface DEM of Vatnajökull from 2010, and a SPOT5 surface DEM of Langjökull from 2004 (Korona et al., 2009; Pálsson et al., 2012). Time–scale for adjustment of glaciers to changes in mass balance. FP, EM, TT, TJ, AG, BE, HB, HH, HHH, and OS have conducted the in situ mass-balance measurements on the three main ice caps. The importance of accurate glacier albedo for estimates of surface mass balance on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations. The European Space Agency (ESA) released a video this past week showing the evolution of two very large and disconcerting cracks in Antarctica’s Pine Island Glacier. The surface mass balance from the glaciological method is obtained by measuring the snow water equivalent (w.e.) Björnsson, H., Pálsson, F., Guðmundsson, M. T., and Haraldsson, H. H. (2002). J. Geophys. The glaciological year 2018/19 was among the most negative mass-balance years that were not significantly impacted by volcanic eruptions but by dust blown onto the glacier surface. 47, 659–664. Front. (1997), Bahr et al. The calving fronts of many tidewater glaciers in Greenland have been undergoing strong seasonal and in-terannual ﬂuctuations. Comparison of mass change rates estimated in this study and studies based on glaciological observations provided to the WGMS database (Zemp et al., 2019; Zemp et al., 2020b) and the GRACE observations (Wouters et al., 2019), with the respective estimated uncertainties. The volumes of Hofsjökull and Vatnajökull in 1945 and 1890 and for Langjökull in 1890 were calculated based on the derived fit (shown with stars in Figure 4). Volume–area scatter plot for the three largest ice caps in Iceland at various times since 1890. The mass loss due to energy dissipation in Vatnajökull, caused by the flow of water and ice as estimated by Jóhannesson et al. Comparison of the glaciological surface mass-balance record of Hofsjökull with results from geodetic mass balance, derived by differencing digital elevation models (DEMs), revealed a bias between the two data sets. TJ contributed the non-surface mass-balance estimates. February 6, 2019 Cracks herald the calving of a large iceberg from Petermann Glacier by Alfred Wegener Institute Satellite immages Petermann glacier. The mass-balance measurements have been conducted at ∼60, ∼25, and ∼25 locations since 1991/92, 1996/97, and 1987/88 for Vatnajökull, Langjökull, and Hofsjökull, respectively. (2020) are in the last version of the WGMS database (10.5904/wgms-fog-2020-08). a−1 is adopted for the smaller glaciers in 1945/46 to 2016/17. Earth Sci., 26 November 2020
Jóhannesson, T., Björnsson, H., Magnússon, E., Guðmundsson, S., Pálsson, F., Sigurðsson, O., et al. Annual and interannual variability and trends of albedo for Icelandic glaciers. The height of the ice is about 3,000 feet, 300-400 feet above water and the rest below water. a−1 (value in 2016/17) for the last two years of the record. Images were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite from 2000 to 2019. The surface and bedrock topographies of the largest ice caps have been measured in radio-echo sounding campaigns carried out since 1977. 9 shares. This corresponds to ∼500 m retreat from the determined LIA extent of Vatnajökull’s surge-type outlets. It was an absolutely stunning phenomenon to witness (and survive) . (2013). doi:10.3189/S002214300000928X, Korona, J., Berthier, E., Bernard, M., Remy, F., and Thouvenot, E. (2009). 65, 395–409. Most glaciers in Iceland reached their greatest historical extent during the LIA, with a maximum recorded in the late 19th century, although some glaciers reached a similar extent already during the 18th century (e.g., Thorarinsson, 1943; Geirsdóttir et al., 2009; Björnsson, 2017; Hannesdóttir et al., 2020, and references therein). On Wednesday, March 6, 2019, two photographers, a model and I headed out onto Portage Lake for a styled bridal shoot. Ann. We thank three reviewers and the scientific editor Michael Zemp for constructive comments on the manuscript. Ice-volume changes, bias estimation of mass-balance measurements and changes in subglacial lakes derived by lidar mapping of the surface of Icelandic glaciers. Conventionally, calving front posi- a−1 to −0.055 m w. e. a−1. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. (2020). Geosci. Saw some awesome and beautiful sights, this was a trip of a life time.! 8, 163. doi:10.3389/feart.2020.00163, Bjørk, A. In the following three years, the mass loss rate was less negative than in the previous years, but the glaciological year 2018/19 was one of the most negative mass-balance years on record, due to the persistence of anticyclonic conditions during the summer of 2019 (Tedesco and Fettweis, 2020), which resulted in warm and sunny conditions from early spring. The moment was shared by Háfjall, a tour company located in Höfn, southeast Iceland. Sigurðsson, O., and Williams, R. (2008). Geophys.
HH, OS, EM, and JB contributed the area estimates at different times. (4) The non-surface mass-balance estimates from Jóhannesson et al. 7, 171. doi:10.3389/feart.2019.00171, Weber, P., Boston, C. M., Lovell, H., and Andreassen, L. M. (2019). Its future after that will depend on how much warming will be realized (Schmidt et al., 2019). The main objective was to derive an estimate for the mass-change history of Icelandic glaciers for the 20th century and the first two decades of the 21st century. Continuity of the mass loss of the world’s glaciers and ice caps from the grace and grace follow-on missions. This value includes both the uncertainty of the volume used as input for the volume–area scaling and the uncertainty of the output values (shown with stars in Figure 4). Huge Cracks in Antarctic Glacier Foreshadow Epic Calving Event. doi:10.1016/j.isprsjprs.2008.10.005, Leclercq, P. W., Oerlemans, J., and Cogley, J. G. (2011). Tech. Nat. Inset figures show a zoom in of the plot for the clusters with data from Hofsjökull and Langjökull (upper left corner) and Vatnajökull (lower right corner). We were pelted with chunks of flying ice and buckets of water. The results presented here add valuable information to global estimates of the response of glaciers to climate change in the past several decades. 5, 427–432. All authors contributed to discussions at various stages of the work and during the revisions of the manuscript. This mass loss corresponds to 1.50 ± 0.36 mm sea level equivalent or 16 ± 4% of mass stored in Icelandic glaciers around 1890. 66, 313–328. Guðmundsson, S., Björnsson, H., Pálsson, F., Magnússon, E., Sæmundsson, Þ., and Jóhannesson, T. (2019). Mass balance of Mýrdalsjökull ice cap accumulation area and comparison of observed winter balance with simulated precipitation. 1 Thank kennethj133 . The outlines of glaciers in Iceland published by Hannesdóttir et al. The record spans 129 years, although the annual variability is not available until the last two decades of the 20th century. SPOT6/7 data were obtained thanks to public funds received in the framework of GEOSUD, a project (ANR-10-EQPX-20) of the program “Investissements d’Avenir” managed by the French National Research Agency. Thankfully this dude wasn’t blown off his boat into the frigid waters and came away with some incredible footage. Most of these advance between a few hundred meters and several kilometers during surges (Björnsson et al., 2003), the average probably being close to 1 km. Surges of glaciers in Iceland. *Correspondence: Guðfinna Aðalgeirsdóttir, firstname.lastname@example.org, Front. J. Int. This bias has been corrected in the surface mass-balance record of Hofsjökull (Jóhannesson et al., 2013; Thorsteinsson et al., 2017) shown in Figure 2, taking into account the contribution of the non-surface mass balance. Østrem, G., and Brugman, M. (1991). Rev. (2013). Values for the ratio F are specifically calculated for the periods 1994/95–2003/04, 2004/5–2009/10, and 2010/11–2016/17 (1.176, 1.131, and 1.056, respectively), corresponding to the geodetic mass-balance periods of Belart et al. Ann. Seven additional glaciers in Iceland are larger than 10 km2, and there are presently around 250 smaller glaciers, many of them in the central north highlands (Tröllaskagi (Trö) in Figure 1). doi:10.5194/tc-14-1209-2020, Thorarinsson, S. (1940). doi:10.1016/j.cosust.2013.11.003. Ash generation and distribution from the April–May 2010 eruption of Eyjafjallajökull, Iceland. The Pine … In 1930/31 to 1949/50, the average loss rates were probably close to the ones observed since 1994, while in 1980/81–1993/94, Icelandic glaciers had a period of small but significant surplus (1.5 ± 1.0 Gt a−1). The editor and reviewers' affiliations are the latest provided on their Loop research profiles and may not reflect their situation at the time of review. (2019) is shown in Figure 6. [Dataset]. 35, 355–369. The blue markers are for Langjökull, green markers for Hofsjökull, and the black for Vatnajökull. 11
a−1 higher mass loss from the glaciological method compared with the geodetic method. For best impressions, visit Glacier Bay, Hubbard Glacier, Sawyer Glacier in Tracy Arm Fjord, Mendenhall Glacier, or the glaciers of College Fjord. 115, F01010. The net mass change during these periods, which is obtained with the geodetic method, is not altered by this. The detailed mass-balance record presented here is combined from glaciological observations, geodetic measurements, simulation with the HIRHAM5 snowpack model, estimates of non-surface mass balance, and results from an empirical volume–area scaling that are used to extend the record back to the time of maximum LIA extent of the glaciers as recorded by geomorphological evidence. J. Geophys. (2005). Brief communication: global reconstructions of glacier mass change during the 20th century are consistent. Zamolo, A. ISPRS J. Photogramm. To say we are lucky to be alive is an understatement. Thirty to forty terminus positions are measured annually and the observations are posted on the website spordakost.jorfi.is. The future mass loss will both be due to the already realized temperature increase (Mernild et al., 2013; Vaughan et al., 2013; Marzeion et al., 2018) and the projected continued warming. doi:10.1002/2016GL071485, Gärtner-Roer, I., Naegeli, K., Huss, M., Knecht, T., Machguth, H., and Zemp, M. (2014). Below we justify the above uncertainties and this approach. No use, distribution or reproduction is permitted which does not comply with these terms. (1997) for ice caps. Jökull 49, 29–46. Available at: doi:10.17895/ices.pub.4625 (Accessed March 21, 2018). In case the glacier surface and subglacial topographies are well known at one point in time, the computation of volume changes can be based on an accurate estimate of the glacier volume at that time and the method mainly relies on the assumption that there is a statistical relationship between volume and area changes (see Figure 4). Received: 18 January 2019 – Discussion started: 7 February 2019 Revised: 23 May 2019 – Accepted: 6 June 2019 – Published: 28 June 2019 Abstract. Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland. nowa et al. doi:10.5194/tc-9-139-2015, Østby, T. I., Schuler, T. V., Hagen, J. O., Hock, R., Kohler, J., and Reijmer, C. H. (2017). Holocene and latest Pleistocene climate and glacier fluctuations in Iceland. Many glaciers started retreating from an advanced position near their LIA terminal moraines in the last decades of the 19th century, even if they reached the absolute maximum extent somewhat earlier. The areal extent at several times for all the glaciers has been estimated based on a data set of glacier outlines (Pálsson et al., 2012; Jóhannesson et al., 2013; Hannesdóttir et al., 2020). Earth Sci. (2020) includes geothermal melting, energy dissipation caused by the flow of water and ice, volcanic eruptions, and calving. When adding the non-surface mass-balance component from Jóhannesson et al. Notice that there are times when the front appears to stay in the same place or even advance, though the overall trend is toward … (2012). a−1. Lett. Glaciers and ice caps: vulnerable water resources in a warming climate. Persistent albedo reduction on southern Icelandic glaciers due to ashfall from the 2010 Eyjafjallajökull eruption. Report No. (E) The average summer (June through September) temperature at the meteorological station in Stykkishólmur (see Figure 1 for location); the thick line shows the 11-year running average with triangular weight, a 5-year filter. Afkomumælingar á Hofsjökli 1988–2017 (mass balance Measurements on Hofsjökull 1988–2017). (2012). 2). (2013). Editors Caseldine, C., Russell, A., Harðardóttir, J., and Knudsen, O. Glaciol. The non-surface melting of glaciers in Iceland for the period 1995–2019 estimated by Jóhannesson et al. Articles. By Francis Xavier | August 15, 2019 11:53 am If you go kayaking in Alaska trying to witness a calving glacier you might get more than you bargained for. Env. The mass change record of each glacier is constructed from three to four methods. (2019). Pálsson, F., Guðmundsson, S., Björnsson, H., Berthier, E., Magnússon, E., Guðmundsson, S., et al. More recently, the ocean around Iceland warmed after 1995 which correlates with the enhanced mass loss after 1995 in Iceland (Björnsson et al., 2013, this study) and Norway (Andreassen et al., 2020). 111, F03001. WGMS 2020. Past and future sea-level change from the surface mass balance of glaciers. Hofsjökull and Langjökull, which currently have more negative specific mass balance than Vatnajökull and are both smaller in area and with less ice thickness, are likely to lose about 60 and 80% of their mass, respectively, until the year 2100 (Guðmundsson et al., 2009; Thorsteinsson et al., 2013). The retreat of many glacier tongues was noticed in the early 20th century and in 1930 a country-wide voluntary monitoring program was initiated (Eyþórsson, 1963; Sigurðsson, 2005). The data records are shown in Figures 2 and 3A,B,C. Geophys. (2011). Although the glaciers in Iceland are located in a highly active volcanic region, they are useful monitors of climate variations. a−1, while the corresponding number for Hofsjökull and Langjökull is determined to be 0.07 m w.e.