KAZALCI OKOLJA

Key message
Bad

The quick rate of retreat of the Triglav Glacier, which began in the second half of the 20thcentury, further accelerated till the beginning of the 21st century. Due to increasing intensity of ice thinning, outcropping rocks began to emerge in the middle of the glacier, which disintegrated into two parts in 1992. In the last part of the first decade of the 21st century, the glacier has been retreating at a slower rate. The last major recession of the glacier was registered after the above average hot summer of 2003. The process stalled in years with above-average snow cover height in late spring, but just in the case of constant snow accumulation during the whole snow season.


This indicator shows changes in the surface area and volume of the Triglav glacier in the period 1992–2020 (volume measurements are periodical, the last one was in 2013) and the average decade temperature of the melting season (May–October) at Kredarica in the period 1961–2020. The cumulative specific mass balance of selected European glaciers in the period 1946 – 2020 is presented as well. The measured surface area of the Triglav glacier includes glacier ice as well as snow directly above or adjacent to the glacier unless indicated otherwise. Glacier ice is entirely exposed at the end of the melting season only on rare occasions and only exceptionally for the period of several consecutive years.

Mass balance is the difference between accumulation and ablation of ice or snow covering the glacier. Due to variable density of snow and ice, it is expressed in millimeters of water equivalent. Specific mass balance means an average value per unit of surface area.

A glacier is a perennial mass of ice on the Earth’s surface that moves downslope under its own weight in response to gravitational force. A glacier forms above the snow line in locations where the mass accumulation of snow and ice exceeds ablation over many years. The snow is gradually transformed into glacier ice, which moves downslope reaching below the snow line until the glacier ice disappears due to prevailing ablation. The Triglav glacier because of its smallness doesnʹt have any more all the glacier characteristics; for this kind of small glaciers (smaller than 25 ha) the term glacieret is enforced (Cogley and the others, 2011). The key factors of ablation are: sun radiation (intensity, duration), air temperature, precipitation and wind (Gabrovec, Zakšek, 2007).

Changes in glacier volume and extent are an illustrative indicator of climate change. During the last decade, the trend of rapid glacier retreat has been characteristic of all Alpine glaciers. In Slovenia, there are two small glaciers, remnants of former glaciers: the Triglav glacier and the Skuta glacier. Due to their extreme south-eastern position within the Alps and low altitude, both are exceptionally sensitive to climate change. Due to the small size of both Slovenian glaciers, their relative retreat in respect to their present extent and volume is even greater than in other Alpine glaciers. Dating of subglacial carbonate deposits and its existence at the edge of today's Triglav Glacier show, that the glacier could have persisted since the end of the Pleistocene glaciation (Lipar and others, 2021) about 12,000 years ago and therefore did not form in the Little Ice Age, the colder period between 14th and 19th centuries, as assumed until now.


Charts

Figure PP05-1: Changes in the Triglav glacier surface area, 1992-2020
Sources:

ZRC SAZU, Anton Melik Geographical Institute, 2021. (8. and 9.9.2021)

Show data
surface[ha]
1992 4.30
1995 3
1999 1.10
2003 0.70
2005 1.10
2007 0.60
2008 1.10
2009 2.90
2010 2.50
2011 2.40
2012 0.60
2013 2.50
2014 3.60
2015 1.70
2016 1
2017 0.70
2018 0.80
2019 0.60
2020 1.30
Figure PP05-2: Changes in the Triglav glacier volume, 1992-2013
Sources:

ZRC SAZU, Anton Melik Geographical Institute, 2021. (8. and 9.9.2021)

Show data
Volume[(1000m3)]
1992 400
1999 60
2005 20
2008 10
2013 7.40
Figure PP05-3: Extent of the Triglav glacier, 1946-2020
Sources:

ZRC SAZU, Anton Melik Geographical Institute, 2021. (25. 03. 2021)

Show data
Figure PP05-4: Average decade temperatures of the melting season at Kredarica between 1961 and 2020
Sources:

Slovenian Environment Agency, 2021 (25. 03. 2021)

Show data
Average temperature of the melting season[oC]
1961-1970 3.30
1971-1980 2.70
1981-1990 3.70
1991-2000 3.80
2001-2010 4.20
2011-2020 4.70
Figure PP05-5: Cumulative specific net mass balance of selected glaciers, Europe, 1946-2016
Sources:

World Glacier Monitoring Service, 2021 ( 25.3. 2021)

Show data
Careser (IT)[mm w.e.] Gries (CH)[mm w.e.] Hintereis (AT)[mm w.e.] Saint Sorlin (FR)[mm w.e.] Sarennes (FR)[mm w.e.] Vernagtferner (AT)[mm w.e.] Storglaciaeren (SE)[mm w.e.] Nigardsbreen (NO)[mm w.e.] Austre Broeggerbreen (NO)[mm w.e.] Aalfotbreen (NO)[mm w.e.] Hofsjokull N (IS)[mm w.e.] Maladeta (ES)[mm w.e.]
1946 -1130
1947 -3190
1948 0 -3190
1949 -2990 -2290
1950 -4610 -3580
1951 -4410 -4230
1952 0 -6030 -4390
1953 -540 -6670 -5200
1954 -826 -7220 -6170
1955 -750 -6560 -6330
1956 -1025 0 -7160 -6810
1957 -1214 -360 -7680 -7130
1958 -2195 -330 -8350 -7780
1959 -2958 -1540 -9610 -8750
1960 -3020 -1870 -9490 -10360
1961 0 -3225 -1760 -9880 -11460 0
1962 -984 -3921 -2860 -10790 -11140 2250 0
1963 -1164 -4524 -2590 -10600 -11330 2030 -1100
1964 -1852 -5768 -4240 -12430 0 -10840 2980 -820
1965 -1407 -4843 -3780 -12400 751 -10410 3890 -340
1966 0 -1764 -4499 -3080 -11980 1383 -10940 2970 0 -1950
1967 -390 -1735 -4479 -3540 -12390 1466 -11170 5130 -650 -670
1968 -130 -1356 -4141 -2730 -12050 1767 -11270 5350 -750 280
1969 -130 -623 -4572 -2290 -12410 1460 -12310 4040 -1680 -1890
1970 -760 -1381 -5124 -2160 -12820 1236 -13830 3480 -2220 -3120
1971 -1410 -1908 -5724 -3010 -13920 812 -14020 4300 -2800 -2180
1972 -1010 -1500 -5798 -3250 -14290 949 -15070 4160 -3110 -2290
1973 -2290 -2595 -7027 -4010 -15160 489 -15020 5260 -3190 -110
1974 -2610 -2773 -6972 -4830 -16760 719 -15360 5740 -4110 920
1975 -2440 -2395 -6907 -4550 -16650 890 -14190 6010 -4420 2130
1976 -2710 -3416 -7221 -5960 -18720 940 -13920 6410 -4870 3660
1977 -1720 -2250 -6461 -4630 -17730 1292 -13720 5640 -4980 3100
1978 -1640 -1194 -6050 -3770 -17180 1580 -13800 5510 -5540 2590
1979 -1820 -2079 -6269 -3540 -17290 1624 -14010 6220 -6250 2460
1980 -1810 -1509 -6319 -2630 -16970 1764 -15280 5000 -6770 1850
1981 -2650 -1833 -6492 -2430 -16930 1709 -15470 5310 -7320 2070
1982 -4330 -3137 -7732 -2890 -17030 864 -15210 4890 -7360 1940
1983 -5120 -3916 -8312 -3030 -17100 327 -14930 5980 -7630 3540
1984 -5710 -3920 -8280 -2650 -17140 347 -14810 6320 -8360 4860
1985 -6470 -4446 -8854 -3120 -18350 235 -15530 6100 -8910 4300
1986 -7610 -5393 -9586 -4690 -20140 -573 -15590 6000 -9230 3890
1987 -9250 -6126 -10303 -5080 -21060 -863 -15110 7480 -9010 5960 0
1988 -10260 -7050 -11248 -4920 -21750 -1360 -15950 6590 -9530 3480 -740
1989 -11080 -8121 -11885 -7350 -24340 -1672 -14710 10060 -9980 6410 -160
1990 -12660 -10109 -12880 -8510 -26480 -2240 -14120 11830 -10640 8200 -760
1991 -14390 -11453 -14205 -9570 -27840 -3319 -13950 12030 -10510 8990 -2170 0
1992 -15590 -12578 -15325 -11310 -29150 -4177 -13070 13630 -10610 11280 -1110 -327
1993 -15890 -13630 -15895 -12280 -30350 -4649 -12070 15480 -11640 13460 -200 -359
1994 -17630 -13839 -17005 -12610 -30980 -5677 -12440 16040 -11800 14240 -120 -8
1995 -18710 -14117 -17465 -11940 -30220 -6075 -11740 17230 -12580 15440 -800 -651
1996 -20030 -14634 -18292 -12450 -30220 -6488 -12130 16820 -12750 13560 -1580 -444
1997 -20960 -15702 -18883 -12610 -30650 -6975 -12760 17290 -13460 13640 -2630 68
1998 -23200 -17755 -20115 -14830 -32990 -7978 -13280 18260 -14320 13750 -3310 -887
1999 -25000 -18319 -20976 -15870 -34050 -8086 -13460 18430 -14680 13810 -3560 -1651
2000 -26610 -19304 -21609 -17110 -35584 -8373 -12880 20150 -14700 15800 -4900 -2551
2001 -26860 -19533 -21782 -16950 -35194 -8597 -13580 19931 -15180 13707 -5480 -2049
2002 -28009 -20523 -22429 -18640 -37514 -8863 -14410 19043 -15760 12177 -6480 -2860
2003 -31326 -23234 -24243 -21590 -40654 -10996 -15450 17884 -16660 9675 -7460 -3962
2004 -32888 -24380 -24910 -24040 -43474 -11403 -15570 17841 -17780 9575 -8820 -5478
2005 -34893 -25892 -25971 -26540 -46754 -11926 -15640 18939 -18780 10243 -9250 -6957
2006 -36986 -27887 -27487 -27980 -49134 -12808 -17360 17540 -19510 7053 -9760 -8744
2007 -39731 -29360 -29285 -30230 -51654 -13774 -16950 18587 -19967 8323 -10150 -9691
2008 -41582 -30961 -30519 -32040 -53994 -14617 -16370 19687 -20097 9003 -10720 -9729
2009 -42919 -31844 -31701 -34690 -57894 -15576 -16900 19917 -20350 8853 -11070 -11143
2010 -43858 -33151 -32521 -35690 -59424 -16256 -17590 19117 -20790 7013 -13470 -10884
2011 -45780 -35301 -33940 -38710 -63577 -17211 -18650 18286 -21794 6168 -13790 -12388
2012 -45780 -35301 -33940 -38710 -63577 -17211 -18650 18286 -21794 6168 -13790 -12388
2013 -48240 -37341 -35501 -40840 -66267 -18366 -17970 19560 -21969 7529 -14250 -14859
2014 -49279 -37883 -36011 -41796 -67637 -18791 -19380 19328 -23019 6625 -14610 -14469
2015 -49410 -40113 -36133 -43136 -69547 -18935 -20270 18985 -23009 4972 -15560 -14391
2016 -1748 -1191 -1263 -1140 -1510 -781 -240 486 -1450 -635 -1130 -843
2017 -2747 -2437 -1826 -2640 -3001 -1335 470 587 -790 -750 -610 -1672
2018 -1981 -2045 -1963 -2020 -1960 -1419 -1600 -852 -880 -2036 240 257
2019 -1432 -865 -680 -2880 -3140 -929 -310 -266 -710 -2439 -1320 -1582
2020 -1371 -1218 -970 0 -100 -820 -140 1608 -1740 959 -390 -212

Goals

  • To adapt to climate change and to reduce potential negative impacts.
  • To adopt urgent measures to combat climate change and its consequences.
  • To promote adaptation to climate change in key vulnerable sectors.
  • To encourage Member States to adopt measures for protection against climate change.

Similar oscillations within the last 400 years are typical of all Alpine glaciers. Following their peak at the beginning of the 17th century, glaciers remained at their maximum extent for the next 250 years, undergoing relatively insignificant changes. Most glaciers in the eastern Alps reached their second peak between 1770 and 1780, and in the mid-19th century. However, the post-1920 period records a continuous retreat of glaciers; the only variations occurring between individual years and decades were those concerning the rate of glacier retreat.

The melting of the Triglav glacier intensified during the 1990’s. The increasingly rapid thinning of the glacier ice caused individual rock formations to appear in the middle of the glacier, finally cutting it into two completely separate parts in 1992. The melting and disintegration of the Triglav glacier is still continuing, with occasional halts in the process occurring in years with exceptionally high snow cover during late spring. This occurred e.g. in 2004, when, at the beginning of July, snow measurement rods below the glacier revealed more than 2 m of snow. The snow cover remained in place until the end of the ablation season, so the glacier remained covered by snow and the measurements made no sense. The snow remained at the bottom of the glacier until the end of summer 2005, which is why the glacier’s surface area in this year was greater than in 2003. The smallest glacier area before 2018 was recorded in 2007, when it measured 0.6 ha. At the end of the melting season in 2008, the glacier was still mainly covered with snow from the previous winter season, and its measured surface area therefore amounted to 1,1 ha. The most significant glacier recovery occurred in 2009 and 2014, mostly thanks to above-average snow cover during two consecutive winters of 2008/09–2009/10 and 2012/13–2013/14, during which numerous avalanches were triggered as well. They are also among the important factors that make a glacier or its existence possible. At the end of the melting season in 2010, when most of the glacier was covered with thick layers of old snow, the glacier’s surface area was 2.5 hectares. It was similar at the end of the melting season in 2014, when it measured 3,6 hectares.

It should be borne in mind that the increase at that time was the result of several months of glacial firing or the well-reclaimed old snow of the last snow season. Due to the specific geographic location of the Triglav glacier, the latter has been only at the beginning of the years or even decades long process of the formation of the greenish firn ice, which gave the glacier the almost forgotten name "Green snow".

In September 2013, georadar measurements were carried out (13 cross sections with a length of 40–82 m in the NNE–SSW direction). They revealed that the surface area of glacier ice was 0.38 hectares (2.5 hectares including the snow on top of and adjacent to the glacier), while its volume amounted to 7,400 m3. The greatest thickness in some places was 5 m and the average thickness was 1.95 m. Including the snow on top of and adjacent to the glacier, the greatest thickness was 8 metres, while the average thickness was no more than 3 metres.

The trend of ice build-up stopped during the melting season in 2015, when the glacier's surface area was reduced by more than 50 %, to 1.7 hectares. Its thickness, and consequently its volume, was reduced even more (several metres in places). All of the firm that accumulated at previous years (more exactly from the beginning of the snow season 2005/06 with some spaces until the end of snow season 2013/14) disappeared due to intensive melting. Two seasons with snow volumes below average which were followed by very warm summers, caused further intense melting of the firn originating from previous winters, leading to contraction and thinning of the glacier. Even the snow season of 2017/18, which was pretty above average and which largely coincides with "the growing age" of the glacier (November-April) didn't stop this trend, as we subsequently recorded the warmest average melting season temperature since 1955, i.e. since the Krearica data are available. All of the 11 warmest melting seasons fall in the period after 2000. Out of 5 hottest, 4 happened after the year 2012. The warmest melting season was recorded in 2019.

Within the period 2017–2019 the surface of the glacier was again smaller than one hectare. The maximal thickness of the glacial layer nowhere exceeds 5 meters at the end of the melting period. Only a patch of glacial ice caught in a karst depression remains, which is by the specific volume density increasingly similar to water ice.

The precise time determination of disappearance the glacier is impossible, because it isn't possible to be accurate enough in the prediction of the local climate change on  the Triglav glacier area. The latter is a result of the global climate change. With the continued occurrence of unfavourable climatic conditions in the coming years, there is a strong likelihood that the glacier will disintegrate into several smaller parts and disappear gradually. Even during the last survey in 2020, two "islands" of rocky surface appeared in the middle of the glacier.

When measurements began in the mid-1950s, the melting period was slightly shorter than the accumulation period, while in recent decades it has usually been the opposite. The glacier balance is very fragile, as current temperature conditions and other factors threaten the preservation of the Triglav glacier (table Average temperature (° C) melting season at Kredarica in decades). If atmosphere warming continues at the rate witnessed in the last two decades, the glacier will eventually disappear. More snowfall in the area of the glacier, which is a possible result of global climate change, will only temporarily delay the glacier's gradual disappearance.

Data from a nearby meteorological station in Kredarica show that the average melting season temperature has a rather large year-on-year variability, with a marked upward trend, which is consistent with observed patterns of temperature change at other stations in the Alps. After a fairly stable average in the 1950s and 1960s, the minimum was in the 1970s. At the beginning of the 1980s temperatures began to rise during the melting season and this trend continued into this millennium. A comparison of 10-year series of average melting season temperatures (May-October) during the period 1961–2020 shows the first two major temperature jumps in the second half of the 80's and the second one at the beginning of the 21st century (1.0 and 0.4 respectively).  The average temperature of the melting season of the next, in the last ten-year series (2011–2020), increased by 0.5 ° C compared to the previous one.

The highest average melting season temperatures between 1955 and 2020 were recorded at 5.6 ° C in 2019 (0.4 ° C higher than in the extremely warm year and the summer of 2003) and the lowest (1.7 ° C) in years 1972 and 1974. The average temperature of the last melting season (May-October 2020) was with 4.4 ° C just above to the long-term average (4.3 ° C) of the last climatological period (1991-2020). The rather cold October or the last month of the melting season stands out. The melting seasons in 2012, 2017 and 2019 was also outstandingly warm (for a whole degree of Celsius too hot) relative to the comparative data for the climatological period.  A possible turnaround for glacier growth would require a sequence of sub-average melting seasons or a series of very snowy winters. However, it canʹt be overlooked, that since the beginning of the yearlong measurements at Kredarica (1955), as many as 11 warmest melting seasons fall in the period after 2000. In the first half of this 66-year observation period, almost all the melting seasons are from 2000 onwards, with the exception of 2010 and 2014. In the last period the glacier initially increased significantly-in 2013 and 2014. But in the next two years it reduced again and reached the surface decades ago. A significant decrease in glacier thickness or volume in the last years was aided by relatively late (March) snowfall in the accumulation period and the above-average warming period, since four (June-September) of all six months were well above long-term average; the only exception was the severely cold September 2017. Last year (2020) the shrinkage temporarily stopped.

If the favourable conditions observed in the period 1992-2007 and in 2011, 2012, 2015 and 2016-2018 recur in coming years the glacier will continue to shrink. In this case the glacier may again disappear completely, which almost already happened at the beginning of this millennium. This is why the Triglav glacier will continue to be extremely important and one of the direct indicators of climate change in the region. Similar movements are typical of all Alpine glaciers. The largest mass losses were also recorded in the Sarennes (France), Careser (Italy) and the Hintereis (Austria) glaciers in 1946-2020. Simultaneously mass increased in some Norwegian glaciers (Nigardsbreen), also on Maladeta,  in the Pyrenees of Spain. Variations in the rate of change are caused by varying altitude, location and the size of glaciers in addition to the variable annual weather factors.

From 1900 until today, according to the European Environment Agency data, the Alps have lost about 50 % of their ice mass, mainly due to elevated  summer temperatures. The continued retreat of glaciers is predicted during the 21st century. According to the moderately optimistic scenario of RCP4.5 releases, the extent of European glaciers will decrease from 20 to 84 % until the year 2100 (compared to the year 2006). The pessimistic PCP 8.5 emission scenario forecasts the reduction of 38-89 %. The largest relative volume loss is expected in central Europe, while in Norway the glacier areas are expected to decrease by about third till the end of the century, according to the SRES B2 greenhouse gas emissions scenario.

 


Methodology

Date of data source summarization