Paraglacial response of steep, sediment-mantled slopes to post-‘Little Ice Age’ glacier recession in the central Swiss Alps

The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains the third largest ice volume outside of the Greenland and Antarctic ice sheets, and contributes more to global sea level rise than any other glacierised region defined by the Randolph Glacier Inventory. However, ice loss in this area is not linear, but in part controlled by glacier hypsometry as valley and outlet glaciers are at risk of becoming detached from their accumulation areas during thinning. Plateau icefields, such as Juneau Icefield in Alaska, are very sensitive to changes in Equilibrium Line Altitude (ELA) as this can result in rapidly shrinking accumulation areas. Here, we present detailed geomorphological mapping around Juneau Icefield and use this data to reconstruct the icefield during the &#8220;Little Ice Age&#8221;. We use topographic maps, archival aerial photographs, high-resolution satellite imagery and digital elevation models to map glacier lake and glacier area and volume change from the Little Ice Age to the present day (1770, 1948, 1979, 1990, 2005, 2015 and 2019 AD). Structural glaciological mapping (1979 and 2019) highlights structural and topographic controls on non-linear glacier recession.&#160; Our data shows pronounced glacier thinning and recession in response to widespread detachment of outlet glaciers from their plateau accumulation areas. Glacier detachments became common after 2005, and occurred with increasing frequency since then. Total summed rates of area change increased eightfold from 1770-1948 (-6.14 km2 a-1) to 2015-2019 (-45.23 km2 a-1). Total rates of recession were consistent from 1770 to 1990 AD, and grew increasingly rapid after 2005, in line with regional warming.

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Holocene Glacial and Tree-Line Variations in the White River Valley and Skolai Pass, Alaska and Yukon Territory

Quaternary Research ◽

10.1016/0033-5894(77)90014-x ◽

1977 ◽

Vol 7 (1) ◽

pp. 63-111 ◽

Cited By ~ 96

Author(s):

George H. Denton ◽

Wibjörn Karlén

Keyword(s):

20Th Century ◽

Little Ice Age ◽

Yukon Territory ◽

Summer Temperature ◽

River Valley ◽

Ice Age ◽

The Arctic ◽

Tree Line ◽

White River ◽

Glacier Recession

Complex glacier and tree-line fluctuations in the White River valley on the northern flank of the St. Elias and Wrangell Mountains in southern Alaska and Yukon Territory are recognized by detailed moraine maps and drift stratigraphy, and are dated by dendrochronology, lichenometry,14C ages, and stratigraphic relations of drift to the eastern (123014C yr BP) and northern (198014C yr BP) lobes of the White River Ash. The results show two major intervals of expansion, one concurrent with the well-known and widespread Little Ice Age and the other dated between 2900 and 210014C yr BP, with a culmination about 2600 and 280014C yr BP. Here, the ages of Little Ice Age moraines suggest fluctuating glacier expansion between ad 1500 and the early 20th century. Much of the 20th century has experienced glacier recession, but probably it would be premature to declare the Little Ice Age over. The complex moraine systems of the older expansion interval lie immediately downvalley from Little Ice Age moraines, suggesting that the two expansion intervals represent similar events in the Holocene, and hence that the Little Ice Age is not unique. Another very short-lived advance occurred about 1230 to 105014C yr BP. Spruce immigrated into the valley to a minimum altitude of 3500 ft (1067 m), about 600 ft (183 m) below the current spruce tree line of 4100 ft (1250 m), at least by 802014C yr BP. Subsequent intervals of high tree line were in accord with glacier recession; in fact, several spruce-wood deposits above current tree line occur bedded between Holocene tills. High deposits of fossil wood range up to 76 m above present tree line and are dated at about 5250, 3600 to 3000, and 2100 to 123014C yr BP. St. Elias glacial and tree-line fluctuations, which probably are controlled predominantly by summer temperature and by length of the growing and ablation seasons, correlate closely with a detailed Holocene tree-ring curve from California, suggesting a degree of synchronism of Holocene summer-temperature changes between the two areas. This synchronism is strengthened by comparison with the glacier record from British Columbia and Mt. Rainier. Likewise, broad synchronism of Holocene events exists across the Arctic between the St. Elias Mountains and Swedish Lappland. Finally, two sequences from the Southern Hemisphere show similar records, in so far as dating allows. Hence, we believe that a preliminary case can be made for broad synchronism of Holocene climatic fluctuations in several regions, although further data are needed and several areas, particularly Colorado and Baffin Island, show major differences in the regional pattern.

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Post-glacial dynamics of alpine Little Ice Age glacitectonized frozen landforms (Swiss Alps)

10.5194/egusphere-egu2020-18360 ◽

2020 ◽

Author(s):

Julie Wee ◽

Reynald Delaloye ◽

Chloé Barboux

Keyword(s):

Little Ice Age ◽

Spatial Configuration ◽

Sar Interferometry ◽

Swiss Alps ◽

Ice Age ◽

Permafrost Degradation ◽

Mass Wasting ◽

Ground Ice ◽

Slope Movements ◽

Glacier Ice

Glaciers and frozen debris landforms have coexisted and episodically interacted throughout the Holocene, the former having altered the development, spatial distribution and thermal regime of the latter. In the Alps, the apogee of last interaction phase occurred during the Little Ice Age (LIA). Since then, due to glacier shrinkage, interactions between glaciers and LIA pre-existing frozen debris have gradually diminished and are leaning towards being non-existent. Post-LIA glacier forefields in permafrost environments, including associated glacitectonized frozen landforms (GFL) have shifted from a thermal and mechanical glacier dominant regime towards a periglacial or even post-periglacial regime. GFL are undergoing thermal and mechanical readjustments in response to both the longer-term glacier recession and the more recent drastic climatic warming. They can be expressed by a combination of mass-wasting processes and thaw-induced subsidence.&#160;In various regions of the Swiss Alps, slope movements occurring in a periglacial context have been inventoried in previous works using differential SAR interferometry (DInSAR) (Barboux et al., 2014). In the scope of this study, and focusing solely on mass-wasting GFL, the former inventory allowed the identification of the latter under various spatial configurations within LIA glacier forefields. While most observed GFL are disconnected from the associated glacier, some are still connected. Additionally, ground ice occurs as interstitial or massive (buried) glacier ice. This potentially infers the ongoing of non-uniform morphodynamical readjustments.&#160;To understand the site-specific behaviour of GFL, the analysis of long-term time-series of permafrost monitoring and multi-temporal high-resolution Digital Elevation Models will allow the assessment of the recent evolution of the Aget and Ritord/Challand LIA glacier forefields (46&#176;00&#8217;32&#8217;&#8217; N, 7&#176;14&#8217;20&#8217;&#8217; E and 45&#176;57&#8217;10&#8217;&#8217; N, 7&#176;14&#8217;52&#8217;&#8217; E, respectively) and their associated GFL (i.e. push-moraines). Both glacier forefields present a contrasting spatial configuration, making their morphodynamical evolution to differ partly from one another. The Aget push-moraine is a back-creeping GFL, which has been disconnected from the Aget glacier since the 1940s at latest. For the last two decades, surface displacement velocities have decelerated in comparison to the accelerating regional trend (PERMOS, 2019). Additionally, a 30% decrease of the electrical resistivity of the frozen ground, combined with locally observed thaw-induced subsidence of up to 10 cm/year suggest an advanced permafrost degradation. The Ritord/Challand system presents a push-moraine disconnected from its glacier as well as several push-moraines connected to a still existing debris-covered glacier. Between 2016 and 2019, surface lowering up to 10 m attesting massive ice melt has been locally detected in the former where buried glacier ice was visually observed. Whereas in the latter, subtle surface displacements ranging from 10 to 30 cm/year occur. This confirms the heterogeneity of the morphodynamical processes occurring in GFL, expressed as a function of both their spatial configuration and ground ice properties.&#160;Barboux, C., Delaloye R. and Lambiel, C. (2014). Inventorying slope movements in an Alpine environment using DInSAR. Earth Surface Processes and Landforms, 39/15, 2087-2099.PERMOS 2019. Permafrost in Switzerland 2014/2015 to 2017/2018. Noetzli, J., Pellet, C., and Staub, B. (eds.), Glaciological Report (Permafrost) No. 16-19 of the Cryospheric Commission of the Swiss Academy of Sciences, 104.

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‘Little Ice Age’ maxima and glacier retreat in northern Troms and western Finnmark, northern Norway

10.5194/egusphere-egu2020-3905 ◽

2020 ◽

Author(s):

Joshua Leigh ◽

Chris Stokes ◽

David Evans ◽

Rachel Carr ◽

Liss Andreassen

Keyword(s):

Little Ice Age ◽

Ice Age ◽

Early 20Th Century ◽

Main Study ◽

Remotely Sensed Data ◽

Mountain Glacier ◽

Northern Norway ◽

Glacier Recession ◽

Proglacial Lakes ◽

Main Study Area

Glaciers are important indicators of climate change and observations worldwide document increasing rates of mountain glacier recession. Here we present ~200 years of change in mountain glacier extent in northern Troms and western Finnmark. This was achieved through: (1) mapping recent (post-1980s) changes in ice extent from remotely sensed data and (2) lichenometric dating and mapping of major moraine systems within a sub-set of the main study area (the Rotsund Valley). Lichenometric dating reveals that the Little Ice Age (LIA) maximum occurred as early as AD 1814 (&#177;41 years), which is before the early-20th century LIA maximum proposed on the nearby Lyngen Peninsula, but younger than the LIA maximum limits in southern and central Norway (ca. AD 1740-50). Between LIA maximum and AD 1989, the reconstructed glaciers (n = 15) shrank by 3.9 km2 (39%), with those that shrank by >50% fronted by proglacial lakes. Between AD 1989 and 2018, the total area of glaciers within the study area (n = 219 in AD 1989) shrank by ~35 km2. Very small glaciers (<0.5 km2 in AD 1989) show the highest relative rates of shrinkage, and 90% of mapped glaciers within the study area are <0.5 km2 as of AD 2018.

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On the incidence of debris flows from the early Little Ice Age to a future greenhouse climate: A case study from the Swiss Alps

Geophysical Research Letters ◽

10.1029/2006gl026805 ◽

2006 ◽

Vol 33 (16) ◽

Cited By ~ 85

Author(s):

Markus Stoffel ◽

Martin Beniston

Keyword(s):

Debris Flows ◽

Little Ice Age ◽

Swiss Alps ◽

Ice Age ◽

Greenhouse Climate

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Climatic variation and runoff in mountain basins with differing proportions of glacier cover*

Hydrology Research ◽

10.2166/nh.2006.017 ◽

2006 ◽

Vol 37 (4-5) ◽

pp. 315-326 ◽

Cited By ~ 16

Author(s):

David N. Collins

Keyword(s):

Air Temperature ◽

Little Ice Age ◽

Climatic Variation ◽

Ice Age ◽

Precipitation Data ◽

Climatic Fluctuation ◽

Temperature And Precipitation ◽

Glacier Recession ◽

Mountain Basins ◽

High Elevations

Records of discharge from partially-glacierised basins in the upper Rhône catchment, Switzerland, were examined together with air temperature and precipitation data in order to assess impacts of climatic fluctuation and percentage glacierisation of basin on runoff, as glaciers declined from dimensions attained during the Little Ice Age. Above 60% glacierisation, year-to-year variations in runoff mimicked mean May–September air temperature, rising in the warm 1940s, declining in the cool 1970s, before increasing (by 50%) into the warm dry 1990s/2000s but not reaching 1940s maxima. In basins with between 35–60% glacierisation, flow also increased into the 1980s but waned through the 1990s. With less than 2% glacierisation, the pattern of runoff was broadly the inverse of that of temperature and followed precipitation, dipping in the 1940s, rising in the cool wet late 1960s, and declining into the 1990s/2000s, with glacier melt in warm years being insufficient to offset lack of precipitation. On mid-sized glaciers at relatively low elevations and with limited vertical extent, in warmer years, the transient snow line was above the highest point of the glacier. Only on large glaciers descending from high elevations can rising transient snowlines continue to expose more ice to melt. Runoff from such large glaciers was enhanced in warm summers but reduction of overall ice area through glacier recession led to runoff in the warmest summer (2003) being lower than the previous peak discharge recorded in the second warmest year (1947).

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A chronology of the Little Ice Age in the tropical Andes of Bolivia (16°S) and its implications for climate reconstruction

Quaternary Research ◽

10.1016/j.yqres.2008.02.012 ◽

2008 ◽

Vol 70 (2) ◽

pp. 198-212 ◽

Cited By ~ 52

Author(s):

Antoine Rabatel ◽

Bernard Francou ◽

Vincent Jomelli ◽

Philippe Naveau ◽

Delphine Grancher

Keyword(s):

20Th Century ◽

Little Ice Age ◽

18Th Century ◽

Extreme Values ◽

Ice Age ◽

Tropical Andes ◽

Equilibrium Line Altitude ◽

Mountain Areas ◽

Study Region ◽

Glacier Recession

AbstractDating moraines by lichenometry enabled us to reconstruct glacier recession in the Bolivian Andes since the Little Ice Age maximum. On the 15 proglacial margins studied, we identified a system of ten principal moraines that marks the successive positions of glaciers over the last four centuries. Moraines were dated by performing statistical analysis of lichen measurements based on the extreme values theory. Like glaciers in many mid-latitude mountain areas, Bolivian glaciers reached their maximal extent during the second half of the 17th century. This glacier maximum coincides with the Maunder minimum of solar irradiance. By reconstructing the equilibrium-line altitude and changes in mass-balance, we think the glacier maximum may be due to a 20 to 30% increase in precipitation and a 1.1 to 1.2 °C decrease in temperature compared with present conditions. In the early 18th century, glaciers started to retreat at varying rates until the late 19th to early 20th century; this trend was generally associated with decreasing accumulation rates. By contrast, glacier recession in the 20th century was mainly the consequence of an increase in temperature and humidity. These results are consistent with observations made in the study region based on other proxies.

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Glacier recession on Cerro Charquini (16° S), Bolivia, since the maximum of the Little Ice Age (17th century)

Journal of Glaciology ◽

10.3189/172756506781828917 ◽

2006 ◽

Vol 52 (176) ◽

pp. 110-118 ◽

Cited By ~ 32

Author(s):

Antoine Rabatel ◽

Abraham Machaca ◽

Bernard Francou ◽

Vincent Jomelli

Keyword(s):

20Th Century ◽

Little Ice Age ◽

17Th Century ◽

Climatic Conditions ◽

Ice Age ◽

Equilibrium Line Altitude ◽

Glacier Recession ◽

Recession Rates ◽

Cordillera Real ◽

The 19Th Century

AbstractCerro Charquini, Bolivia (Cordillera Real, 5392 ma.s.l.) was selected as a site to reconstruct glacier recession since the maximum of the Little Ice Age (LIA) in the central Andes. Five glaciers, located on differently exposed slopes, present comprehensive and well-preserved morainic systems attributed to former centuries. The moraines were dated by lichenometry and show a consistent organization on the different slopes. The past geometry of the glaciers was reconstructed using ground topography and aerophotogrammetry. Lichenometric dating shows that the LIA maximum occurred in the second half of the 17th century, after which the glaciers have receded nearly continuously. Over the last decades of the 20th century (1983–97), recession rates increased by a factor of four. On the northern and western slopes, glaciers receded more than on the southern and eastern slopes (by 78% and 65% of their LIA maximum area, respectively). The mean equilibrium-line altitude (ELA) rose by about 160 m between the LIA maximum and 1997. Recession rates were analysed in terms of climatic signal, suggesting that glacier recession since the LIA maximum was mainly due to a change in precipitation and that the 19th century may have been drier. For the 20th century, a temperature rise of about 0.6°C appears to be the main cause of glacier recession. Recent climatic conditions from 1983 to 1997 correspond to a mass deficit of about 1.36m w.e.a–1. If such conditions persist, the small glaciers below 5300ma.s.l. in the Cordillera Real should disappear completely in the near future.

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Evolution of the Norwegian plateau icefield Hardangerjøkulen since the ‘Little Ice Age’

The Holocene ◽

10.1177/0959683619865601 ◽

2019 ◽

Vol 29 (12) ◽

pp. 1885-1905 ◽

Cited By ~ 6

Author(s):

Paul Weber ◽

Clare M Boston ◽

Harold Lovell ◽

Liss M Andreassen

Keyword(s):

Little Ice Age ◽

Substantial Reduction ◽

Length Change ◽

Ice Age ◽

Outlet Glacier ◽

Climate Fluctuations ◽

Relative Dating ◽

Glacier Recession ◽

Map Interpretation

The maximum ‘Little Ice Age’ (LIA) glacier extent provides a significant baseline to assess long-term glacier change and to place currently observed rates of glacier recession in a broader temporal context. To that end, we examine the evolution of the plateau icefield Hardangerjøkulen since the LIA. First, we reconstruct Hardangerjøkulen’s maximum LIA extent (~AD 1750) and subsequent recession based on the glacial landform record and aided by historical map interpretation. Ice-marginal moraines, glacial drift limits, trimlines, and identifiable erosion and weathering boundaries provide evidence of a LIA icefield with an area of 110 km2. Existing LIA model simulations of Hardangerjøkulen are not yet fully able to reproduce our reconstructed extent. Second, we compile a set of remotely sensed icefield outlines from successive time points in the 20th and 21st century to calculate icefield area and length change since the LIA. This reveals a substantial reduction in icefield size, with a total area loss of 41 km2 (37%; 2% 10 a–1) by 2010 and a cumulative frontal retreat averaging 1.3 km (29%; 5 m a–1) by 2013. Icefield recession has been greatest since the end of the 20th century, when rates of areal shrinkage increased to 6.5–10% 10 a–1 in 1995–2010, and the rate of average terminus retreat accelerated to 17 m a–1 in 2003–2010. Third, we present a relative dating approach, based on the known age of the different icefield outlines, that allows bracketing ages to be assigned to all ice-marginal landforms between any two outlines. This approach shows that episodes of moraine formation vary temporally between individual outlet glaciers of Hardangerjøkulen, suggesting that the moraine record of a single outlet glacier alone may not be sufficient to derive an icefield-wide picture of past ice advances, and thereby climate fluctuations.

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