Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe

Abstract

Abstract. Glaciers worldwide are shrinking at an accelerated rate as the climate changes in response to anthropogenic influence. While increasing air temperature is the main factor behind glacier mass and volume loss, variable patterns of precipitation distribution also play a role, though these are not as well understood. Furthermore, while the response of surface glaciers (from large polar ice sheets to small alpine glaciers) to climatic changes is well documented and continuously monitored, little to nothing is known about how cave glaciers (perennial ice accumulations in rock-hosted caves) react to atmospheric warming. In this context, we present here the response of cave and surface glaciers in SE Europe to the extreme precipitation events occurring between May and July 2019 in SE Europe. Surface glaciers in the northern Balkan Peninsula lost between 17 % and 19 % of their total area, while cave glaciers in Croatia, Greece, Romania and Slovenia lost ice at levels higher than any recorded by instrumental observations during the past decades. The melting was likely the result of large amounts of warm water delivered directly to the surface of the glaciers, leading to rapid reduction in the area of surface glaciers and the thickness of cave glaciers. As climate models predict that such extreme precipitation events are set to increase in frequency and intensity, the presence of cave glaciers in SE Europe and the paleoclimatic information they host may be lost in the near future. Moreover, the same projected continuous warming and increase in precipitation extremes could pose an additional threat to the alpine glaciers in southern Europe, resulting in faster-than-predicted melting.

Radiocarbon Constraints on Periods of Positive Cave Ice Mass Balance During the Last Millennium, Julian Alps (Nw Slovenia)

“…In addition, a late Holocene record from a Croatian stalagmite indicates drier conditions in the Central Adriatic during this period (Rudzka et al 2012). The shift towards drier summers during MW2 may have counter-balanced the effect of elevated summer temperatures altogether by mitigating the advection of sensible heat from warm rain events, as reported by Perşoiu et al (2021).…”

“…Such loss has been recognized in many ice caves worldwide with a lost ice volume between 1908 and 2010 AD estimated at about 23,000 m 3 (Kern and Perşoiu 2013). Substantial ice loss was recently reported from ice caves of southeastern Europe, with the extreme rainfall events of summer 2019 likely playing a key role in the accelerated demise of these ice bodies (Perşoiu et al 2021). In the specific case of M-17, we propose that exceptional rainfall at the beginning of November 2019 played a key role in opening the connection from the ice chamber to c/d doline and allowing forced convection between the two entrances.…”

“…The formation of small 10-cmdeep bédières (surface water channels) advects infiltration and melt water to the ice-free outskirts of the main chamber. This process is significant with respect to the annual ice mass-balance, since it removes ponded water otherwise available for refreezing during the cold season, as noted in the case of Scărişoara ice cave by Perşoiu et al (2021).…”

“…In this study, wood fragments as well as individual trunks were sampled primarily from layers rich in organic matter, interpreted as unfavorable for positive ice mass balance. Substantial ice loss in recent years (Kern and Perşoiu 2013), accelerated by extreme precipitation events (Perşoiu et al 2021) which are expected to increase under climate scenarios RCP4.5 and RCP8.5 (Púčik et al 2017) underscores the vulnerability of this unique archive.…”

A Review of Ice Core Drilling in Cave Environment – Challenges, Achievements and Future Directions

“…The flow is further complicated by the uneven melting at the sole and sides of the ice blocks and the morphology of the surrounding walls, so that folds and tilting of the ice layers up to the vertical (Figure 2) are a common occurrence (Perşoiu and Pazdur, 2011;Spötl et al, 2014). Additionally, as most of the ice caves are located close to or well below the altitude of the 0 °C isotherm, annual melting affects both the surface and sides of the ice blocks, with extreme ablation events possibly leading to the ablation of several years' worth of annual accumulation (Colucci et al, 2016a;Perşoiu et al, 2021). Ablation could affect either the entire surface of an ice block or only part of it, and also acts on time scales ranging from years to centuries.…”