An evaluation of high-altitude and –latitude diurnal frost environments: South

Africa, Marion Island & Antarctica

Introduction

Geomorphology is considered a multivariate scientific field1, where a number of processes may yield similar forms or particular process-

es yield specific forms 2. While specific processes need to be investigated, it is often challenging to isolate these in geomorphic regimes.

Since proposed by Büdel 3, it has long been thought that climatic zones control specific geomorphological processes 4 and features 5 spe-

cific to a zone, yielding morphoclimatic and morphogenetic zones 4. Climatic geomorphologists believe that processes inherent to each

climate zone will engender characteristic regional patterns and landforms. Zonality is a core concept in climatic geomorphology, where

climatic zones control mechanical and chemical weathering 6. However, criticism has arisen regarding the premise of climatic geomor-

phology. Research by e.g. Sumner et al. 6 has indicated that similar geomorphic features occur in different climates and that geomorphic

effects may be similar across climate zones. Criticism of climatic geomorphology, therefore, arises from the azonal processes of landform

creation 7–9, the inconsistency of classifying and oversimplification of climatic zones 10, a failure to establish process-form and climate-

form links, the uncertainty in determining meteorological/climatic inputs and geomorphic processes on a temporal scale 11, the presence

of relict landforms 11, and the failure to approach the subject in a holistic manner 2. The classification systems of climatic zones (e.g.

Büdel, Köppen-Geiger-Pohl, Thornthwaite) on specific criteria, such as temperature, precipitation, soil distribution and/or vegetation has

resulted in a number of disparate climatic zones. The exclusion of vegetation in many of these systems is a matter of concern, as vegeta-

tion cover in particular has been identified as a limiting factor in e.g. frost environments, having a negative feedback on periglacial sys-

tems 12. This is further compounded by the exclusion of other important parameters such as the soil-moisture balance and altitude with-

in the classifications. Furthermore, although average temperature and moisture values are applied, local variations may occur, making

the general assignation of a climate to an area not necessarily appropriate at a number of scales. The generalised approach of climate

geomorphology should, therefore, be combined with the specific approach of the process geomorphologist, with particular attention

given to levels of scale. A conceptual model of the current classification systems, the available selection criteria, as well as parameters

that should be considered is given in Fig. 2.

Setting

Three study sites of varying altitudes; latitudes and broad regional climates are investigated (Fig. 1A), allowing for an investigation into

azonality/zonality. These sites include the Eastern Cape Drakensberg of mainland South Africa (Fig. 1B), Marion Island in the sub-

Antarctic (Fig. 1C) and Western Dronning Maud Land (WDML) and Jutulsessen of the Antarctic (Fig. 1D). Eight sites are located within

WDML and one in the Jutulsessen. Five sites are located on Marion Island and two in the Eastern Cape Drakensberg. The southernmost

study site is located in WDML at Sletfjell (72°08’S), with the northernmost located in the Eastern Cape at Ben MacDhui (30°38'45"S). The

westernmost site is also located in WDML at Flårjuven Bluff at 03°23’W, whereas the easternmost site is located in the sub-Antarctic on

Marion Island (37°45’E). There is a range of 3 000m in altitude and app. 40 degrees in both latitude and longitude. One study site on

Marion Island is located near sea level, whereas Ben MacDhui in the Eastern Cape Drakensberg reaches a height of 3 001m.

Despite disparate climates, common to all three areas are diurnal frost cycles, which are the focus of the study. The different altitude and

latitudes are of interest as both elevation and latitude have been shown to control active layer thickness with an increase in latitude and

altitude resulting in a decrease in depth of freeze events in the ground 13, 14. Continental Western Dronning Maud Land is a polar desert,

Marion Island has a hyper-maritime climate 15, and the Drakensberg is an alpine (montane) region 16. For all the study sites there is a

convergence of form, or equifinality, with landform and -features common to all three. Within these climatic zones a further subdivision

may be made in terms of the periglacial environment. The periglacial zones cover ap. 25% of the earth’s surface, spanning the circumpo-

lar zones and found at high altitudes 12, 16, 17. Investigating diurnal frost processes within high-altitudinal and –latitudinal environments

has the potential to provide insight into climatic geomorphological concepts and applications.

Acknowledgements

National Research Foundation—Project funding (Grant SNA2011120400001)

German Academic Exchange Service (DAAD) — Funding

Rhodes University—Funding

South African National Antarctic Programme—Logistical support

Department of Environmental Affairs—Logistical support

Contact Details

First & presenting author: Christel Hansen

g11h7349@campus.ru.ac.za

PO Box 94 Geography Department Rhodes University Grahamstown 6140 South Africa

Findings & Discussion

An investigation into the three separate study areas has shown that diurnal frost cycles are present for all. WDML and the Jutulsessen experi-

ences diurnal freezing and thawing during the summer months. High-frequency, low-magnitude and short diurnal frost cycles are observed for

Marion Island. During one night of May 2014 frost events were observed down to an elevation of app. 120m. Diurnal frost cycles also occur

for Ben MacDhui and evidence of such has been seen down to app. 2550m. Whereas no frost cycles have been recorded for the Elandsberg,

visual evidence of soil frost was seen, indicating that frost only occurs in the upper layers of the ground and not to the depth of the loggers

(2.5cm). Needle ice has been recoded for Marion Island at all logger sites, excepting the logger site at 88m. Furthermore, patterned ground is

in abundance, as are stone and vegetation banked lobes, as well as sorted stripes. Evidence of needle ice has been observed in the field on the

Vesleskarvet nunataks, although these occurrences are rare. In contrast, patterned ground such as thermal contraction polygons, sorted

stripes and sorted circles are relatively common. On the slopes of Ben MacDhui gelifluction lobes, needle ice, patterned ground, stone and

vegetation banked lobes, as well as thúfur are known to occur. All sites experience different climates, vegetation cover (if present), animal and

human presence, as well as varying snow cover. Each also falls within its own climatic zone, depending on which classification system is used.

The presence of similar landforms and processes, however, suggests azonality of processes and landforms. Altitude and latitude in terms of

the annual solar radiation budget appear to be important factors, as is the availability of moisture within the soil (Fig. 2). Vegetation is also

crucial. The Elandsberg is covered by dense grass and low shrubs. Even though this site receives adequate precipitation and experiences in-

tense cold spells, no frost events have been recorded as yet. This suggests that the vegetation cover is sufficient to provide an insulating effect

and/or freeze events are not sufficient to destroy the vegetation cover.

Conclusion

Although climatic geomorphology offers a polished approach to landscape studies, it nevertheless has many shortcomings. The premise of cli-

matic geomorphology facilitates a top-down approach that lends itself to generalisation and regional studies 2, 4. Ideally, geomorphic processes

should be investigated to deduce their role in landscape development, facilitating a more base-upwards approach. As such the idea of apply-

ing specific geomorphic processes to specific climatic regimes needs to be re-investigated, in particular as local environmental conditions may

override regional climatic conditions. The role of frost cycles on landform evolution at three climatically and geographically different study

sites is considered. Although Büdel focused on regional processes 10 divisions are essentially limited only by the scale a person is interested in.

The problem arises which scale one should choose. Greater consideration must be given to moisture regimes within these environments 6, 7,.

Incoming solar irradiation must also be considered, as mid- to low latitudes receive greater direct insolation, yielding higher temperatures.

Furthermore, a rise in altitude is found to be equivalent to an increase in latitude when investigating frost processes. Landforms develop due

to the interrelation of many factors and processes active within each zone (relief, climate, geology, hydrology, weathering etc.) and it is argued

that the concept of zonality cannot be universally applied investigating frost-process derived landforms. Instead the general approach of re-

gional studies should be combined with the specific approach of the process geomorphologist, in order to yield a refinement of applying cli-

matic geomorphological concepts to geographical zones.

Fig. 1:

A) The entire study area is shown, as are the three study sites for the Eastern Cape Drakensberg (1), sub-Antarctic Marion Island (2), and Western Dronning Maud Land and the Jutulsessen in the Antarctic (3).

B) The Eastern Cape Drakensberg with Ben MacDhui and Elandsberg indicated. The sites range from 1420m-2987m in altitude.

C) Sub-Antarctic Marion Island with five logging sites shown. These sites range from 770m-88m.

D) Western Dronning Maud Land and ten study locations are indicated. The inset represents the study location at Troll station in the Jutulsessen. The sites range from 356m-1435m in altitude.

Fig. 2:

A conceptual model for the identification of climatic zones. Current classification are indicated, as well as criteria that should be applied when identifying climatic zones.

HANSEN, CD 1, MEIKLEJOHN, K.I.1, and NEL, W.2 1 Department of Geography, Rhodes University, GRAHAMSTOWN, SOUTH AFRICA

2 Department of Geography and Environmental Science, University of Fort Hare, EAST LONDON, SOUTH AFRICA

A B

D C

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