Field Trip to Ice Age Museum

The most interesting Quaternary geomorphology story of Norway

1 Introduction

Glaciers, a slowly moving mass or river of ice, have shaped the landscapes, scouring out rock and sediments and depositing thick debris. This process over a period is called glaciation. The warm inter-period or process, during which glacier retreat, is deglaciation.

Instead of being only tourist attractions, glaciers and their geomorphic conditions have strong ties to human society, including culture, economics, water resources and climate concerns and so on. This report aims to present the glacial and periglacial geomorphology story of Norway with the materials from the field trip of GEO4410, 2022 and the follow-up lab exercises. The main objectives are to illustrate:

1.1 The glacier heritage in figures

Landscape

How glaciers have changed Norway? Here are some figures.

Ice sheets, or glaciers in milder periods largely affected the Norwegian landscape, from dramatic western coastlines, deep valleys and fjord to alpine relief. The vertical linear glacier erosion along fjords amounts to 1500 m - 2000m. A mean bedrock has been lowered of 520 m through the Quaternary glaciations in Mid-Norway .

The model reconstruction shows there was a huge ice sheet named the Eurasian ice sheet complex (EISC) with a span of over 4500 km during the last glacier period. It extended to as west as Ireland, crossed the entire Scandinavia and Poland, and reached as far as Siberia, covering both land and sea (the North-Barents-Kara Seas). The ice divide was over 2000-2500 m before the Norwegian Channel Ice Stream lowered the ice surface , which means the place where we stand during the trip, the ice divide, was covered bymore than a thousand of meters of the ice sheet.

EISC is just one of the ice sheets near us. There were eight glacial cycles in the past 740 thousand years , probably about 40 cycles in total within Quaternary glaciation. Each time, the new advanced ice sheet removed most of the older deposits and deepen the fjords more. Thus, the Quaternary landscape nowadays is the cumulative result of numerous glacier cycles with the fresh one on the top.

Hydropower

Among European countries, Norway was a relatively late industrializer. By the end of the nineteenth century, only 11.9 percent of the population was employed in manufacturing. The hydropower-related industries boomed after 140 hydropower plants were constructed between 1890-1920.

Now, hydropower produces large amounts (>90%) of clean and cheap electrical energy, so Norwegian’s industry and transportation are benefiting from electrification. For instance, the aluminum industry can sustain competitiveness without bauxite resources in domestic. Moreover, Norway has almost half of Europe’s reservoir capacity. Being a water battery of Europe, Norway is able to balance the deployment of variable renewable energies on all timescales, from seasonal to instantaneous.

Figure 1. The glacier stories in town Odda

The country’s topography contributes to these advantages. Heavy precipitation of 1000 to 3000 mm per year is common in coastal areas when the moist air is uplifted by western mountains. The water is stored at high places where there is no need for resettlements because the lakes and valleys created by glaciers serve as natural reservoirs. The glacier scraped the rock, making it easy to build dams and reducing sedimentation problems in reservoirs .

Odda is a typical industrial town located at the valley’s bottom (Figure 1). It tells two versions of the glacier story. Ringedals dam, one of Europe’s largest gravity dams when it was built in 1909, made Odda famous for its industrial products in the past, which is the old story. In modern times, Odda is more well-known for Trolltunga, a spectacular geological site 700 m above the reservoir, formed by a glacier sliding below.

Agriculture

It takes a long time to sort sediments by water, deposit it in flat areas, and weather it into farmable soil. After the wipe-up of the ice sheets, Norway doesn’t inherit productive soil older than the nearest ice era. Most areas have commonly <1 m sediments cover upon bedrock . Due to climate limitations, wheat was farmed up until the warm medieval era (1100-1300 AD) in southern Norway. Even today Norway does not have any sugar crops. The poor basis of agriculture makes Norway a poor country before the industrial era. On other hand, the will for the self-sustainability of agriculture makes Norway out of European Union in the vote.

Luckily, although being few in size, the precious farmland can still be found upon glaciolfluvial, fluvial sediments and marine deposits in lowland areas adjacent to and under the former ice divided in southeastern Norway, where the average Quaternary sediment thickness is estimated to ca. 6 m, similar to Sweden.

1.2 Beyond the present is the key to the past

During the field trip, we visited Jotunheim and Dovrefjell area in southern Norway. Assuming that the natural processes continue occurring and follow the same laws, we infer what happened in past by what we have seen today. This is a basic geoscience principle:

The present is the key to the past. – Charles Lyell

Today, people are also curious about what can we learn from the past. The past is the key to the future as well. The instability of marine-based ice sheets, e.g. the West Antarctic Ice Sheet today, or EISC back to the LGM, is the tipping element of the climate system. Understanding past responses of ice sheets to past climate change provides an important long-term context for observations of present, and projected future, ice-sheet dynamics.

2 Definition and concepts

As described in the introduction, when there were glaciation & deglaciation events, we need to know when, who and why it happened and how we can study it.

2.1 When

Earth is estimated to be 4.5 billion years old. The IPCC AR6 report described high confidence to assert that the last time CO2 levels were as high as the present was at least 2 million years (Ma) ago. The oldest modern human fossils in Ethiopia were dated around 233 thousand years (kyr) old. All stories need a temporal context (Figure 2).

Figure 2. The time scale, temperature and deglaciation from pre-Quaternary to the present.

On timescales of hundreds of million years, there are five to six ice ages (icehouse conditions), accompanied by periods of little or no ice cover (greenhouse conditions). Now Earth is currently in the Quaternary Ice Age, specifically, an interglacial period of the Quaternary glaciation.

In Scandinavia, old mountain areas were worn down, resulting in the flat surface near sea level, called peneplain in the Paleogene (66 Ma - 23 Ma). Land rose into a mountain plateau (paleic surface) with the fluvial erosional processes in the Neogene period (23 Ma - 2.58 Ma).

The Quaternary period started around 2.58 Ma ago until the present with the fluctuation of climate and glacial cycles, driven by Earth’s orbital variations (now known as Milankovitch cycles). The glacial erosion started dominating.

The Eemian (c.115 kyr) marked the end of the last interglacial and the start of the last glacial period (LGP). In Europe, three ice caps, Celtic, Fennoscandian, and Barents Sea grew in LGP and merged into the Eurasian ice sheet complex (EISC) at the last glacial maximum (LGM, c.27 kyr -20 kyr). EISC transported large sediments from continents to the deep sea and left ice streams channels on the continental shelf, which is proved by data from offshore exploration activities .

The Bølling–Allerød interstadial (c.14.7 kyr - 12.9 kyr) is a short warm period when EISC collapsed and contributed 4.5-7.9 m sea-level rising over 500 years, followed by a sudden cold interruption, the Youngers Dryas (YD, c. 12.9 kyr - 11.7 kyr) for unclear reasons. Some ice sheets and glaciers readvanced in this period. There was an ice sheet covering the present coastlines, and the isostatic depression made the land sinking, such as the Oslo area the marine limit marked the local sea level up to 225 m.

The recent 11.7 kyr is the Holocene epoch. As the remains of EISC, the Fennoscandian ice sheet (FIS) continued retreating and separating into a southern part near Jotunheimen and a larger part in the northern Swedish mountains. FIS finally disappeared at 8.7 kyr with some high-altitude ice remnants.

Climate models show that the Mid-Holocene warm period (c. 9 kyr - 5 kyr) pronounced warming at high latitudes, including Greenland, Western Arctic, and Northern Europe, where the temperature could be 2-3 °C warmer than today. All mountain glaciers in Norway are believed to melt away after this period.

The Vikings established a colony on an island and call it Greenland during the Medieval warm period (1100-1300 AD). But soon, there was the largest glacier oscillation in historical times, the little ice age (16th - 19th centuries). Re-advance of glaciers went down mountains in many records and left margin moraines, e.g. the one we saw in Glacier Storbreen.

1850 AD to the present is under the context of modern climate change. In the future, the detonation of the first atomic bomb in 1945 may mark the beginning of the Anthropocene epoch (1945 - Present).

2.2 Who

Table 1. Glacier erosional and depositional landforms.

Landforms Type Scale Indicate Where or texture
Striae erosion small ice flow bedrock
Rock drumlin erosion medium ice flow bedrock
Roches moutonnees erosion medium ice flow bedrock
Troughs and Fjords erosion large cumulatively bedrock
Cirques erosion large cumulatively bedrock
Fluting moraine medium ice flow Subglacier, hard to preserve
Drumlins moraine meidum ice flow Subglacier
Ribbed terrain moraine medium ice sheet Subglacier
Eskers meltwater medium warm-base,ice margin Subglacier,sorted silts, sands, gravels and boulders
Marginal moraines moraine medium ice margin unsorted
Marginal water channels meltwater medium Cold-base, ice height, ice margin on slope, as a sequence
Potholes meltwater medium Water channels on bedrock or sediments
Ice dammed lakes meltwater - Flood event, lakes origin  
Glacifluvial deposit meltwater - Water channels on delta, outwash,lake bottom. Sorted.

2.2.1 Ice-marginal landforms

When we walk towards a glacier, frequently we see the sediments concentrated in the foreland, including end moraines and glaciofluvial deposits that generally mirror the shape and position of former ice margins.

Figure 3. The west tongue of the Glacier Storbreen

The figure above shows a picture of the glacier Storbreen. The lateral-front moraine (end/ marginal moraine) marked a sequence of the margin of Storbreen from the Little Ice Age to the present. It retreated approximately 1.8 km in around 270 years from 1150 m.s.l. back to 1410 m.s.l. The meltwater channels in the north outlet dissect the moraines, which reminds us the landscape features could be erased or modified by newer processes.

The marginal moraine is an excellent indicator of ice extent as (1) the dating technique can link the location with ages, and (2) marginal moraines are middle-size landforms and can be marked in the field or by DEM and aerial photos.

The marginal (lateral) meltwater channels are other features easy to recognize on the field, which are typically tens of meters deep, meters wide, and hundreds of meters long, and usually form in subparallel down-slope sequences , as shown in Figure below.

If the water cannot reach the bed, perhaps because the glacier is frozen to its bed (polythermal or cold-based glaciers, few temperate-case), the streams may flow to the sides of the glacier, and excavate lateral meltwater channels. Lateral channels may terminate abruptly where the meltwater drained down englacial or subglacial tunnels .

Figure 4. The marginal meltwater channels

2.2.2 Subglacial landforms

Subglacial exhibit a variety of landforms as a result of glacier, glaciofluvial erosion and sediment:

Ice-moulded bedrock: When the ice is sliding upon the bedrock, the abrasion or quarrying process happens, and leaves a polished surface, striae, fractures (Figure 5) and plucked lee side because of the pressure difference. For the same reason but at a bigger scale, rock drumlins or Roches Moutonnee formed.

Ribbed terrain (Rogen moraine), fluting, and drumlins are deposited landforms. The motion of ice led to the deformation of the soft sedimentary bed (Figure 6). And the lee of obstruction on the bed causes the linear features, which vary from fluting to mega-fluting, further to mega-scale glacial lineations(MSGL), drumlins and Rogen moraines.

Figure 5. The abrasion and quarrying process
Figure 6. Rock drumlin(a), Drumlin(b), Fluting(c) and transformation between Rogen moraine and drumlins (d).

Subglacial meltwater channels can form networks, similar to those that form on the ground today. Flow is driven by pressure gradients as well as elevation, so these channels can flow uphill and therefore have undulating long profiles. In contrast to marginal meltwater channels, subglacial meltwater channels are more associated to temperate, wet-based glaciers and ice sheets.

Eskers are sorted sand and gravel ridges in subglacial tunnels deposited by meltwater (Figure 4). Eskers can go uphill because the subglacial meltwater is driven by pressure, which is related to ice thickness rather than the slope of the bed. So, eskers are parallel to ice flow and transverse to the ice terminus and can be used to reconstruct the slope of the ice surface.

Potholes or kettle holes could be found on bedrock or deposited delta.

2.2.3 Proglacial lakes and Ice-dammed lakes

Proglacial lakes, Ice-dammed lakes, shorelines, raised deltas, out-wash and, fluvial sediments are associated with the ice margin landform, providing information on deglaciation patterns.

Where ice margins, either marginal moraine or ice, block the natural drainage of ice-free catchments, water ponding may lead to the formation of ice-dammed lakes . This was common when the ice divide moved to the south of the water dived after LGM. The baltic sea is an ice lake originally (Figure 7).

The shorelines and delta prove the lake’s existence and reflect the water level of the lake. For instance, Grimsmoen is the delta located at the tributary valleys (Figure 7, 8). It covers 13.95 km2 and indicates the water level of the glacial lake Nedre Glåmsjø, which is believed larger than 1500 km2 by Holmsen (1915). However, the map shows that the lake’s extent does not reach Grimsmoen(ca. 700 m.s.l.) because of the Rugldalen spillway (665 m.s.l). The formation of the Grimsmoen delta may be earlier than the lake Nedre Glåmsjø in Figure 7.

Figure 7. Ice divide and ice dammed lake Nedre Glomsjø
Figure 8. Grimsmoen delta marked a big lake in the past

The failure of the dam is triggered by ice retreat, rock avalanche or seismic shock when the lake hydrostatic pressure exceeds the ice overburden pressure at the lake outlet, so call Glacier Lake outburst flood (GLOF). Figure 9 gives an example of the Jutulhogget canyon. The east side valley is 100 m lower than the west side. When the ice sheet melted away, the east side water was released first (Figure 7, outbrust direction) and the canyon was cut into deep water channels by the water from the west side valley.

Figure 9. Jutulhogget canyon

2.2.4 Periglacial landforms

Figure 10. Permafrost-related periglacial landforms. Photos are taken at Juvvatnet (a: a thermokarst lake upon ice-cored moraine, b: large ice-cored moraines in front of small cirque glacier, c: polygons nets ), Dombas (d: palsa).

The thermokarst lake, ice-cored moraine, polygon mark and palsa mire, share a common basis that the permafrost presents below (Figure 10 a,b,c,d).

Permafrost, a thermal concept, refers to the ground that continuously remains below 0 degrees for two or more years. Above the permafrost is the active layer where the seasonal growth of ground ice can break up rocks (so we see angular rock debris), lift the rock, push it and sort it into polygon nets (Figure 10c). The blockfield acts as an efficient heat bridge to cause a negative ground temperature in winter making the process mentioned here go easier.

When the ice lens grows in organic soil, usually wetland, the surface heave like a low hill or knolls. This landform refer to palsa. The thermal offset makes palsa exist in low altitudes as a permafrost boundary. The organic material is saturated, making the surface layer well insulated from heatwaves in summer, but transfers heat after freezing (acts like ice) in winter. The snow distribution driven by wind is also important for the formation of palsa.

Thermokarst is irregular, hummocky terrain, where the subsidence area is often filled with water, hence the name thermokarst lake (Figure 10a).

There was a debate about whether the buried glacier ice should be regarded as rock glacier or ice-cored moraines. argued that the rock glacier is not active sometimes, but the steep slope of ice-cored moraine could move slowly instead. insisted that the rock glacier must move even if it is slow-moving. And the ice-cored moraine is a stationary deposit. However, it is not easy to recognize due to the lack of accurate field measurements and a clear definition of the term ‘rock glacier’. The ice-rich soil on steep slopes in the area of warm permafrost can deform under the influence of gravity due to the creep of pore ice and the migration of unfrozen pore water. This refers to creeping permafrost and permafrost-related hazards.

In summary, water expands by 9% when it freezes. Consequently, in the periglacial environment, the frost cracking, frost sorting, and frost push & pull, drive the vertical and lateral movement or redistribution of land features.

2.3 Why

This section discusses several frameworks for discussing glacial and periglacial environments.

2.3.1 Equilibrium line altitude and permafrost limit

The equilibrium line altitude (ELA) is the point on a glacier where annual accumulation balances annual ablation . The ELA concept connects the most important two variables for glaciers, regional climate and topography. The accumulation is from precipitation mainly in winter, and the ablation is the melt-out mainly in summer. Temperate glaciers have both high snowfall and high melting rates.

The permafrost limit is the outermost (latitudinal) or lowest (altitudinal) limit of the occurrence of permafrost. About -4 °C mean annual air temperature (MAAT) is believed necessary for alpine permafrost in Scandinavian .

In southern Norway, from the western coast to the eastern inland, the ELA is from ca. 1000 m to 2000 m due to the distance to moisture getting longer. However, the permafrost limit decreases towards the east due to climate patterns switching from maritime to continental. Etzelmuller described this as a transition from the predominance of glacial processes to the predominance of permafrost-related processes (Figure 11) . That reflects why the west coast has temperated glaciers and deep fjords, but eastern inland areas have more cold-base landforms, like ice-cored moraines, and marginal meltwater channels.

Figure 11. The comparison of ELA and permafrost limit .

2.3.2 Erosion, debris transport

The glacier buzzsaw hypothesis regarded glaciers as highly effective erosion agents, which are strong enough to limit the mountain height. Bedrock erosion has quarrying and abrasion as two basic mechanisms (Figure 5). Both abrasion and quarring depend on the sliding velocity, in turn, depends on the ice thickness, the ice surface slope, the effective pressure at the bed and the subglacial hydrology. In a word, the rate of erosion is a simple function of the basal sliding speed :

\[\dot{e}=K_{g}\left| u_{s} \right|^l\]

Where ̇e is the erosion rate, u_s is the glacier sliding velocity, K_g is a function of lithology bedrock resistance to erosion and l is an exponent. As the climate varies, the glacier mass balance changes, thereby resulting in changes in glacier length, thickness and velocity, and, in turn, the erosion rate.

During the winter, low temperatures and low melting water reduce sliding, erosion and transport. With an increment of temperature in Spring, the subglacial water becomes pressurized and increases transport, sliding and erosion. Towards to the end of summer, channels are well defined and allow for a higher ice-bed contact, which results in cracks in the bedrock and faster failure along pre-exsiting cracks .

Figure 12. The glacier debris transport

Not just transporting the basal debris, the glacier also transports debris supraglacial, and englacial. The steeper mass balance gradient, the higher velocities, for instance, the marine glaciers in western Norway (Figure 12). Finally, 90% of sediments were transported into the sea. The erosion rate was estimated to be c. 20 cm/kyr based on the volumes of the offshore sediment volumes . However, the erosion of onshore valleys and fjords can only explain 61% - 66 % of the offshore sink volume , which raised debates about the paleosurface and the thickness of the ice sheet.

2.4 How

2.4.1 Dating technique

Schmidt hammer measurements reflect the compressive strength of a rock surface which is assumed to decrease with the degree of rock exposure to subaerial weathering.

The rebound (R) values generated by the Schmidt hammer mirror the rebound velocity of the plunger which was released on the rock surface. Higher R-values are anticipated from freshly exposed rock surfaces. In turn, low R-values are expected from rock surfaces that experienced long exposure . Figure 13, R-values versus altitude, shows that R-value is proportional to altitude in the first 6 groups because the end moraine is older than ‘fresh’ moraine. We infer that the last two group’s samples is young since it may be not from moraine but rock falls instead.

Figure 13. The SHD results in the foreland of glacier Storbreen. Each group contains 10 samples. The elevation profile could be found at Figure 3.

2.4.2 Reconstructure modeling

The geological evidence from the ice margin (proglacial lakes, ice-dammed lakes, end moraines, esker, meltwater channels), combined with ice flow direction(striae, eskers, drumlins, lineations) and ice-free time (erratics, boulders, bedrocks) can describe a proximate extent of the past ice masses but hardly the ice thickness. The varves from lake sediments were used to infer the pace of the deglaciation (Swedish Time Scale). The field evidences are used to constrain the numerical modeling of the ice sheet.

Glacial isostatic adjustment (GIA) modeling focuses on the relative sea level change process. As an ice sheet grows and decays, it transfers a shifting load onto Earth’s crust which responds through elastic and visco-plastic deformation. it is possible to separate the effects of eustatic sea level rise (through ice sheet melting) and isostatic rebound, which can then be used to inversely deduce the history of the ice load .

Ice sheet numerical modeling focus on how the ice reacted to climate change in the past. It turns correct paleoclimate forcing into mass balance over large spatial scales to achieve the ice sheet history of 4D dynamics.

2.4.3 Geophysical observations: ERT and Boreholes

During the field trip, we visited boreholes (129 m and 20 m) at Juvvasshøe on 1 Sept and used electrical resistivity tomography (ERT) to profile the subsurface resistivity near the second boreholes (Figure 14). The widespread polygon nets in the block field denote the permafrost condition (Figure 10c).

Figure 14. The location of ERT profile and boreholes at Juvvasshøe.

ERT

The basis of ERT is that the different materials in the ground have different resistivity, thus electrodes set up on the profile have different current measurements. For example, saturated clay has very low resistance and frozen ground or dry blocky layers have very high resistance.

Figure 15 shows the profile from 2009 and 2019 with notable differences. The purple and reddish indicate the water content, and from yellow to blue may stand for the presence of the ground ice or just dry blocky cracks. In general, the active layer is 2 to 3 meters deep. Except (a) the ground resistance gets lower (dry), (b), (c) and (d) amply more water content in the 2019 case.

Figure 15. ERT profile comparison of 2009 and 2022.

Boreholes

Juvvasshøe borehole site was installed in 1999. We used the data during the period 2008.09.01 to 2019.09.30 in the lab exercise. The mean annual air temperature (MAAT) is -3.63 °C, the mean annual ground surface temperature (MAGST) is -2.76 °C (Figure 16a), and the mean annual temperature at the top of the permafrost (TTOP) is -2.89 °C (Figure 16b). Surface offset is defined as MAGST minus MAAT, and thermal offset is defined as TTOP minus MAGST. The surface offset, 0.84 °C is not significant due to heavy wind in winter and blockfield negative anomaly. The blocky layers have stable thermal conductivity over seasons so the thermal offset is also minimal.

The observations and model suggest that the permafrost exists from -2.89 m to > 350 m. The active layer thickness is not yet increase significant, but likely further go down, as a significant positive trend on the ground surface temperature. Figure 16a is not exactly correct because the linear fit was affected by the sampling effect on the edge.

Figure 16. Juvvasshøe borehole records from 2008 to 2019. (a: Ground surface temperature, b: average temperature curve, c: temperature profile over time, gray is no data)

3 Deglaciation concerns

There were not only approximately 40 glacial cycles in Quaternary but also numerous intra-cycle dynamics in the location and extent of basa thermal zones. So it is extremely complex to deblend the deglaciation events. The numerical models combined with the information from paleo-climate, dating, isostatics adjustment, and offshore sediments with geomorphological datasets as constraints to achieve the ice sheet dynamic history. Figure 17 is one example.

Figure 17. The deglaciation patterns and chronology for the Fennoscandian Ice Sheet .

Some details behind the deglaciation event are closely related to today’s challenges. For instance, scientists are worried about the tipping point of the Antarctic Ice Sheet, the Greenland ice sheet melting, and the permafrost carbon stock. The latest reconstruction revealed the story of the collapse of the EISC.

3.1 The collapse of the EISC

During the LGM, The EISC has a sea level equivalent (SLE) ice volume of ~24 m, which is three times nowadays Greenland Ice Sheet. Large marine-based sectors extended to the continental shelf edge, making EISC a marine ice sheet, similar to West Antarctic Ice Sheet.

An event known as global Meltwater Pulse 1A (MWP-1A) at the Bølling transition ~14,650 years ago had a sea level rising rate of at least 4 cm/year, 12 m -14 m in ~340 years, which is 10 times of today. The previous study concluded the contribution from EISC is SLE ~2.5m during 14.9-12.9 ky BP .

The new reconstruction attributes up to 50% of meltwater to the collapse of EISC. The peak melting of EISC reached SLE ~2.2 cm/year at centennial scales. The authors estimated that the rates of ice loss from the EISC during the early Bølling are comparable to high-end values of mass loss projected for the West Antarctic Ice Sheet in the next centuries. The collapse of EISC reminds us that sudden deglaciation is not a friendly process but possible even if there was no anthropogenic effect but subtle changes in incoming solar radiation by the Earth’s orbit procession.

3.2 The thawing permafrost

Many periglacial landscapes show the imprint of previous glacial conditions. The widespread thawing of permafrost is a consequence and simultaneous event of deglaciation. Particularly, the peatland (palsa, and polygon mires) exists in regions of discontinuous permafrost, and will not be able to survive soon under the latest projection of the warming trend. For instance, the palsa in southern Norway (~1000 m) and northern Noway (~sea level) locates below the permafrost limit (~1300 m for the south, ~600 for the north). In the Finnmark area, the aerial images from the 1950s suggest palsa degradation started as early as the 1950s and decreased 33-71% from the 1950s to the 2010s.

As permafrost is a thermal concept, permafrost loss can be regarded as a function of global warming , which makes the projection of permafrost easier. Figure 18 shows the modern permafrost peatland distributions are expected to shrink. Under Shared Socioeconomic Pathways (SSPs), losses of the suitable climate envelope for palsa/peat plateaus across Europe and Western Siberia by the 2060s of 75% (SSP2-4.5), 81% (SSP3-7.0) and 93% (SPP5-8.5). However, the statistical model does not account for the local variability of the ground thermal regime. Hence it cannot predict the transition lag from MAT to degradation .

Figure 18. Permafrost peat carbon approaching a climatic tipping point .

4 Debates

Glaciers as amplifiers of relief incised Earth’s steepest and highest relief, hence, the low, rolling relief of the high plateaus has been regarded as incompatible with a glacial origin. This led to the old debate about the origin of the low-relief plateaus of southern Norway. There are several versions of the debate but the same questions in fact in a more complex context and across more disciplines in:

The classic theory is that plateaus remnants of paleic lowland surface dating back to Tertiary period. This paleic surface was uplifted and preserved by cold-based ice or as nunatak during glacial periods

4.1 Nunataks hypothesis

Nunataks represents the nonglacier surface protrudes through the thin ice sheet (Nesje et al. 1988). Evidence and criticism:

4.2 Frozen-bed preservation hypothesis

Sugden (1974) noted the importance of relief and basal temperature in developing different landscapes of glacial erosion. Where ice had remained frozen to its bed, there was hardly any erosion. Where deeper valleys had permitted basal melting and thus sliding, they were deepened further while intervening uplands were unaffected. Kleman and Stroeven (1997) demonstrated the selectivity of glacial erosion in the Swedish mountains. This may explain the origin of low-relief plateaus.

Evidence and criticism:

4.3 ICE (isostasy-climate-erosion) hypothesis

The ICE hypothesis ensemble models to explain both erosion problem (the presence of the low relief plateaus) and the offshore sediments problem. The ICE disagrees that there is an old surface neither by nunataks hypotheses nor frozen-bed preservation hypotheses.

Evidence and criticism:

5 Summary of the field trip

This field trip and the related lab exercise give a good description of the process from glacial-to-periglacial environments. The connection between the geomorphology process and nowadays society’s concerns are addressed in the introduction. Then, this report reviewed the common definitions, concepts and methodologies in geomorphology and glacial & periglacial environments.

Figure 19. The overview map of the field trip

The literatures are cited to explain the materials from the field trip. However, except for old debates about ice sheet thickness and/or the paleic surface or the sediment budgets mismatch, there still are several questions that are not clear enough:

In summary, it was a fun field trip, covering so many interesting topics, and connecting everything! Many thanks to Henning, Karianne, Bernd, and Martin for guiding us getting through this Ice Age Museum.