1 Summary of the balance years 2015/16, 2016/17, 2017/18, and 2018/19 (preliminary)

Mass balance values for the observation periods will be reported from more than 130 glaciers worldwide. The mass balance statistics (Table 1) are calculated based on all reported values and on available data from the 40 reference glaciers with continued observation series of more than 30 years (Table 2). In addition, preliminary mass balance values are given for 2018/19 for some glaciers.

The average mass balance of the glaciers with available long-term observation series around the world continues to be negative, with tentative figures indicating a further thickness reduction of 1.0 meters water equivalent (m w.e.) during the hydrological year 2016/17. The new data continues the global trend in strong ice loss over the past few decades and brings the cumulative average thickness loss of the reference glaciers since 1980 at almost 20 m w.e. The current status of glaciers worldwide is summarized here. All so far reported mass balance values, given in Table 3, are tentative.

Table 1: Overview on mass balance data 2015/16, 2016/17, 2017/18 and preliminary values for 2018/19. Statistics are given for all reported glaciers (ALL) and for the available ‘reference’ glaciers with continuous long-term observation series (REF).

2015/16 2016/17 2017/18 2018/19 ALL REF ALL REF ALL REF REF Mean annual mass balance (mm w.e.) -773 -832 -818 -898 -1009 -1248 -1243 Minimum value (mm w.e.) -5545 -2284 -5010 -3001 -3592 -3592 -3400 Maximum value (mm w.e.) +3824 +561 +4725 +1249 +1308 +440 -120 Standard deviation (mm w.e.) 844 622 1071 986 848 849 862 Number of positive/reported balances 16/167 2/38 29/164 8/38 18/151 4/37 0/28

Table 2: Reference glaciers with continuous long-term observation series.

Mountain range Glaciers Alaska Gulkana, Wolverine Pacific Coast Ranges Place, South Cascade, Helm, Lemon Creek, Peyto, Columbia (2057) Andes Echaurren Norte Canadian High Arctic Devon Ice Cap NW, Meighen Ice Cap, White, Melville South Ice Cap Svalbard Austre Broeggerbreen, Midtre Lovénbreen Scandinavia Engabreen, Alfotbreen, Nigardsbreen, Grasubreen, Storbreen, Hellstugubreen, Remebesdalsskaaka (Hardangerjoekulen), Storglaciaeren Alps Saint Sorlin, Sarennes, Argentière, Silvretta, Gries, Stubacher Sonnblickkees, Vernagtferner, Kesselwandferner, Hintereisferner, Caresèr, Wurtenkees Caucasus Djankuat Altai No. 125 (Vodopadniy), Maliy Aktru, Leviy Aktru Tien Shan Ts. Tuyuksuyskiy, Urumqi Glacier No.1

For more detailed analysis of the global mass balance dataset, see the following selected publications and references therein:

Braithwaite, R.J. 2002. Glacier mass balance: the first 50 years of international monitoring. Progr. Phys. Geogr., 26 (1), 76-95.

Cogley, J.G. and W.P. Adams. 1998. Mass balance of glaciers other than the ice sheets. J. Glaciol., 44 (147), 315-325.

Dyurgerov, M.B. 2002. Glacier mass balance and regime: data of measurements and analysis. Boulder, CO, University of Colorado, Institute of Arctic and Alpine Research. INSTAAR Occasional Paper 55.

Dyurgerov, M.B. and M.F. Meier. 2005. Glaciers and the changing Earth system: a 2004 snapshot. Boulder, CO, University of Colorado, Institute of Arctic and Alpine Research. INSTAAR Occasional Paper 58.

Kaser, G., Cogley, J.G., Dyurgerov, M.B., Meier, M.F. and A. Ohmura. 2006. Mass balance of glaciers and ice caps: consensus estimates for 1961-2004. Geophys. Res. Lett., 33 (19), L19501.

Meier, M.F., Dyurgerov, M.B., Rick, U.K., O’Neel, S., Pfeffer, W.T., Anderson, R.S., Anderson, S.P. and A.F. Glazovsky. 2007. Glaciers dominate eustatic sea-level rise in the 21st century. Science, 317 (5841): 1064-1067.

Ohmura, A. 2006. Changes in mountain glaciers and ice caps during the 20th century. Ann. Glaciol., 43, 361-368.

WGMS. 2008. Global Glacier Changes: facts and figures. Zemp, M., Roer, I., Kääb, A., Hoelzle, M., Paul, F. and W. Haeberli (eds.), UNEP, World Glacier Monitoring Service, Zurich, Switzerland: 88 pp.

WGMS. 2013. Glacier Mass Balance Bulletin No. 12 (2010-2011). Zemp, M., Nussbaumer, S.U., Naegeli, K., Gärtner-Roer, I., Paul, F., Hoelzle, M., and Haeberli, W. (eds.), ICSU (WDS) / IUGG (IACS) / UNEP / UNESCO / WMO, World Glacier Monitoring Service, Zurich, Switzerland: 106 pp., publication based on database version: doi: 10.5904/wgms-fog-2013-11.

WGMS. 2012. Fluctuations of Glaciers 2005-2010 (Vol. X): Zemp, M., Frey, H., Gärtner-Roer, I., Nussbaumer, S.U., Hoelzle, M., Paul, F. & W. Haeberli (eds.), ICSU (WDS)/ IUGG (IACS)/ UNEP/ UNESCO/ WMO, World Glacier Monitorings Service, Zurich, Switzerland. Based on database version doi: 10.5904/wgms-fog-2012-11.

Zemp, M., Hoelzle, M. and W. Haeberli. 2009. Six decades of glacier mass balance observations – a review of the worldwide monitoring network. Annals of Glaciology, 50A018.

Zemp, M., Frey, H., Gärtner-Roer, I., Nussbaumer, S.U., Hoelzle, M., Paul, F., Haeberli, W., Denzinger, F., Ahlstroem, A.P., Anderson, B., Bajracharya, S., Baroni, C., Braun, L.N., Caceres, B.E., Casassa, G., Cobos, G., Davila, L.R., Delgado Granados, H., Demuth, M.N., Espizua, L., Fischer, A., Fujita, K., Gadek, B., Ghazanfar, A., Hagen J.O., Holmlund, P., Karimi, N., Li, Z., Pelto, M., Pitte, P., Popovnin, V.V., Portocarrero, C.A., Prinz, R., Sangewar, C.V., Severskiy, I., Sigurdsson, O., Soruco, A., Usubaliev, R., and Vincent, C. (2015): Historically unprecedented global glacier decline in the early 21st century. Journal of Glaciology, 61 (228), p. 745-762. doi: 10.3189/2015JoG15J017

2 Mass balance data

Table 3: Reported mass balance values of the observation period 2015/16, 2016/17, 2017/18 as well as *preliminary values for 2018/19. Principal investigators are listed for submitted data of 2017/18.