Late Pleistocene glaciers to present-day snowpatches: a review and research recommendations for the Marrakech High Atlas

Abstract

There are no glaciers today in the High Atlas, Morocco. However, there is evidence that niche glaciers and late-lying snowpatches in the High Atlas were present as recently as the last century and there are at least four sites where snowpatches appear to survive some summer seasons today. Many other sites also support non-perennial late-lying snow below steep shaded north and northeast-facing cliffs at altitudes > 3100 m. Coarse sediment ridges interpreted as moraines or pronival ramparts enclose most of these snowpatches. These landforms most likely record the positions of former niche glaciers and late-lying snowpatches in the Little Ice Age. The niche glaciers and late-lying snowpatches survived below the regional equilibrium line altitude because of strong local topoclimatic controls. In addition to strong shading, many of the current late-lying snowpatches are fed by long deep gullies which funnel avalanching snow from the cirque backwalls. The disappearance of many perennial snowpatches in the last few decades coincides with a strong trend towards warmer summer air temperatures since the 1970s (> 2 °C). However, inter-annual changes in snowpack mass balance are affected by very large variations (> 400% variability) in winter precipitation. A new research programme is underway investigating the history of late-lying snow and cirque glaciers in the High Atlas. A particular focus of this research is to utilise geomorphological and geochronological evidence to understand fluctuations in snow and ice through the Holocene and link this to continuous records of environmental change in the High Atlas region.

Palynological evidence from a sub-alpine marsh of enhanced Little Ice Age snowpack in the Marrakech High Atlas, North Africa

“…The indirect evidence from wetland proxies for significantly enhanced year-round snowpack in the recent past is consistent with climatic, topographical and historical insights suggesting that present day conditions are close to a climatic threshold permitting year-to-year snow and ice accumulation in the highest cirques of the High Atlas (Hughes 2014(Hughes , 2018Hannah et al 2017;Vieira et al 2017;Hughes et al 2020). The findings encourage further consideration of the Little Ice Age concept in the High Atlas setting.…”

“…A semi-permanent snowpatch has been reported at a similar altitude on the north face of the Tazaghart plateau to the southwest, sustained by avalanching snow into shaded north-facing gullies (Hughes 2014(Hughes , 2018Hannah et al 2017). In fact, late-lying snow is observed at numerous sites across the High Atlas (Hughes et al 2020). Snow is therefore a key control on the hydrology of the alpine zone in the High Atlas, buffering the drying effects of high temperatures, high insolation and low summer precipitation via snowmelt contribution.…”

“…3b). The pattern of very high inter-annual variation of precipitation is common across the High Atlas (Hughes et al 2020). However, since the mountains are largely ungauged and have large altitudinal variability with significant proportions of precipitation falling as snow, the actual precipitation over high elevations remains challenging to determine with high accuracy (Tuel et al 2020).…”

“…While current observations and modelling highlight the sensitivity of the High Atlas snowpack to climatic change (Marchane et al 2017), little is known about the state of the cryosphere in Northwest Africa during the Holocene. Documentary, observational and geomorphological evidence points to more extensive permanent snowfields and even niche glaciers during the Little Ice Age (Hughes 2014(Hughes , 2018Hannah et al 2017;Hughes et al 2020). However, the understanding of Holocene changes in snow and ice cover and resulting environmental impacts remains limited.…”

Regional Geography of Glacier Mass Balance Variability Over Seven Decades 1946–2015

“…Scotland and Montenegro are associated with similar precipitation maxima, but glaciers are absent today in Scotland although snow patches occasionally survive the summer (Manley, 1971), and only niche glaciers exist in Montenegro and neighbouring Albania (Hughes, 2007(Hughes, , 2009. In the Younger Dryas, there were many glaciers in Scotland and the western Balkans, which are both presently very wet, and also in the subtropical mountains of North Africa, which is presently very dry with occasional snow patches (Hughes et al, 2018(Hughes et al, , 2020. (New et al, 1999) interpolated to glacier median altitude for glaciers with >4 years of record in 1946-2015.…”