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Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated periglacial landforms in an attempt to establish a local mid-/late-Holocene chronology for the Geirangerfjellet in South Norway. Landform ages were obtained by application of a local calibration curve for Schmidt hammer R-values based on young and old control points comprising fresh road cuts and a bedrock surface in proximity to the study area, respectively. The area was deglaciated ~11.5 ka ago according to independent age information. Investigation of age, formation and stabilization of the periglacial landforms and processes involved allowed assessment of the underlying Holocene climate variability and its relationship to landform evolution. Our SHD ages range from 7.47 ± 0.73 ka for glacially abraded bedrock at the valley bottom to 2.22 ± 0.49 ka for surface boulders of a rock-slope failure. All landforms shared negative skewness and largely have narrow tailed frequency distributions of their R-values. This points to either substantial reworking of the boulders within a landform or continuous debris supply. Our results show that most landforms stabilized during the Holocene Thermal Maximum (~8.0–5.0 ka). The findings do not support the hypothesis that rock-slope failures predominately occur shortly after local deglaciation. Instead, it appears that they cluster during warm periods due to climate-driven factors, for example, decreasing permafrost depth or increasing cleft-water pressure leading to slope instabilities. Periglacial boulder-dominated landforms in the western maritime fjord region seem to react sensitively to Holocene climate variability and may constitute valuable but to date mostly unexplored sources of palaeoclimatic information. [ABSTRACT FROM AUTHOR]

Two rock glaciers in the valley head of Irishman Stream in the central Ben Ohau Range, Southern Alps/New Zealand, have been investigated using the electronic Schmidt-hammer (SilverSchmidt). Longitudinal profiles on both features reveal a consistent trend of decreasing R(Rebound)-values and, hence, increasing weathering intensity and surface-exposure age on their numerous transverse surface ridges from rooting zone towards the front. Previously published numerical ages obtained by terrestrial cosmogenic nuclide dating (TCND) allowed the calculation of a local Schmidt-hammer exposure-age dating (SHD) age-calibration curve by serving as the required fixed points. Age estimates for the lowermost rock glacier surface ridges fall within the early Holocene between 12 and 10.5 ka and indicate a fast disappearance of the Late Glacial glacier formerly occupying the valley head, followed by the initiation of rock glacier formation around or shortly after the onset of the Holocene. Although it cannot be judged whether the rock glaciers investigated were active within the entire Holocene or only repeatedly during multiple episodes within, their location and intact morphology exclude any substantial glacial activity at Irishman Stream during the Holocene. This has considerable regional palaeoclimatic implications because it opens for the hypothesis that climatic conditions during early Holocene were possibly comparatively dry and favourable for rock glacier initiation, but less so for glaciers. It would also challenge the view that air temperature is the sole major climate driver of glacier variability in the Southern Alps. More work utilising the palaeoclimatic potential of rock glaciers in the Southern Alps is advised. [ABSTRACT FROM AUTHOR]

Chronological studies applying Schmidt-hammer exposure-age dating (SHD) were performed on six glacier forelands in the western part of the Southern Alps, New Zealand. Although lithological heterogeneity prevented a regional age-calibration curve to be established, local age-calibration curves for La Perouse Glacier and Strauchon Glacier could be derived. They show similar linear equations and trends/slopes and enabled a preliminary assessment of the representativeness of individual 10Be terrestrial cosmogenic nuclide dating (TCND)-ages obtained from the other forelands. No mid- and early-Holocene advance periods were detected. Clusters of moraine ages date around 2800, 1850–1450, and 1100–900 years ago, followed by the ‘Little Ice Age’ commencing c. 500 years ago. There is no good agreement with earlier radiocarbon-based studies and recently published TCND-chronologies. As it will be outlined, this partly could be the result of different approaches to the palaeoclimatic interpretation of the dated samples. The results obtained from this recent study do not support an elsewhere proposed general asynchronous glacier behaviour between the mid-latitudinal Northern and Southern hemispheres. [ABSTRACT FROM AUTHOR]

In the context of reconstruction of Holocene glacier chronologies, there has been a clear tendency during the past few decades towards imprecise use of the term ‘high resolution’. Furthermore, it seems to be increasingly assumed that recently developed terrestrial cosmogenic nuclide dating (TCND) is replacing earlier dating methods. Although recent glaciological knowledge clearly reveals the futility of oversimplified global and inter-hemispheric correlation on the basis of few ‘key’ sites, such comparisons are widely attempted. Stimulated by the example of a recently published article relating to the Southern Alps of New Zealand (Schaefer et al., 2009, Science 324: 622—625) we highlight some related potential problems with the interpretation of Holocene glacier chronologies. In particular, we consider (1) that the term ‘high resolution’ should be applied only to decadal-scale resolution or better and, therefore, not to TCND-based chronologies; (2) that discontinuous moraine chronologies should not be termed high resolution and that their potential geomorphological limitations should be acknowledged; and (3) that TCND-based moraine chronologies should not automatically replace evidence available from other dating techniques but that they should be regarded as complementary and an opportunity for mutual evaluation. Owing to local and regional patterns in glacier response to climate, it is concluded (4) that intra-hemispheric synchroneity in high-resolution Holocene glacier variations is still unproven, and hence (5) that inter-hemispheric comparison is arguably premature, if not impossible. Finally, it is suggested (6) that the first priority for research in this field should be to establish the spatial patterns in glacier behaviour evident at various scales in Holocene records. [ABSTRACT FROM PUBLISHER]

The steep outlet glaciers of Jostedalsbreen, western Norway, are good examples of sensitively reacting maritime mountain glaciers. Their changes in length, frontal position and lower tongue's morphology during the past 20 years have been well documented. At first they experienced a strong frontal advance. After AD 2000 glacier behaviour was dominated by a strong frontal retreat, in some cases causing a separation of the lowermost glacier tongue. In this paper, the glacier length changes are presented both visually and numerically, supplemented by mass balance and meteorological data. The glacier behaviour is interpreted and its causes are discussed. Whereas the factors controlling the advance during the 1990s seem clear, the interpretation of the most recent retreat still leaves some uncertainties. The actual glacier front behaviour cannot fully be related to the mass balance data. Terminus response times and relations between individual mass balance and meteorological parameters have changed. Some hypotheses are given, including disturbance of the 'normal' mass transfer and dynamical response of the glacier front because of excessive ablation on the lowermost glacier tongues and summer back melting. These findings underline the sensitivity of maritime glaciers to climate changes. The empirical findings need to be taken into account in the interpretation of recent glacier length changes and their future modelling. [ABSTRACT FROM AUTHOR]

Lichenometric dating studies using the yellow-green Rhizocarpon subgenus at the Eugenie, Hooker, Mueller and Tasman Glaciers in Mt Cook National Park, Southern Alps, New Zealand, reveal a 'Little Ice Age' maximum during the mid-eighteenth century (around AD 1725–1740). Lichenometric dating curves, constructed for Mueller Glacier in a preliminary study, were modified using local control points at the other glaciers. Modification was necessary because of variations in local ecological conditions. The 'Little Ice Age' chronology is similar for three out of the four glaciers studied. All except Tasman Glacier underwent a major glacier front oscillation directly following the 'Little Ice Age' maximum. After a slow but constant retreat during the second half of the eighteenth and the first half of the nineteenth centuries, the glaciers experienced major readvances during the second half of the nineteenthcentury (around AD 1860 and 1890/95), and during the early decades of the twentieth century. Tasman Glacier, as the exception, returned to its 'Little Ice Age' maximum frontal position during the late nineteenthcentury, overtopping pre-existing 'Little Ice Age' moraines, and therefore preventing detailed dating of these moraines. Differences in dating from previous lichenometric studies may be due to the different methods used. [ABSTRACT FROM AUTHOR]

New results concerning the dating of 'Little Ice Age' glacier variations at Svartisen and Okstindan, northern Norway, are presented. Measurements of lichens of the Rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves. These are partly 'adjusted' in relation to well-established lichenometric dating curves from southern Norway. The 'Little Ice Age' maximum at Svartisen and Okstindan is thereby dated to the mid-eighteenth century (i.e., in agreement with southern Norway). Previously suggested earlier 'Little Ice Age' advances are demonstrated to have resulted from an underestimation of the growth rates of the Rhizocarpon subgenus. Synchroneity of 'Little Ice Age' maxima in southern Norway and at Svartisen and Okstindan suggest that a north-south migration of latitudinal depressional tracks can be excluded as the main forcing factor. As an alternative, an increased SE-NW trend of moist airflow in winter parallel to the coast of Norway is suggested as the main forcing factor with recent glacier dynamics in response to recent climatic fluctuations supporting this hypothesis. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530 m above sea level, with an estimated mean annual air temperature of ~1.6°C, currently exhibit deformation attributed to viscous creep. Five years of InSAR measurements for six lobes demonstrate average surface velocities of 1.2–22.0 mm/year with maximum rates of 17.5–55.6 mm/year. New Schmidt-hammer exposure-age dating (SHD) of two proximal lobes reveals mid-Holocene ages (7.6 ± 1.3 ka and 6.0 ± 1.2 ka), which contrast with the early-Holocene SHD and 10Be ages obtained previously from distal lobes, and late-Holocene SHD ages presented here from two adjacent talus slopes (2.3 ± 1.0 ka and 2.4 ± 1.0 ka). Although passive transport of boulders on the surfaces of these small, slow-moving rock glaciers affected by compressive flow means that the exposure ages are close to minimum estimates of the time elapsed since lobe inception, disturbance of boulders on rock glaciers is a source of potentially serious underestimates of rock-glacier age. Rock-glacier development at Øyberget began shortly after local deglaciation around 10 ka before present and continued throughout the Holocene in response to microclimatic undercooling within the coarse blocky surface layer of the talus and rock-glacier lobes. We suggest this enhanced cooling lowers mean annual surface-layer temperature by at least ~3.6°C, which is needed at such a low altitude to sustain sporadic permafrost and avoid fast thawing as atmospheric temperatures rise. Our results point to circumstances where inferences about rock glaciers as indicators of regional climate should be interpreted with caution, and where they may be less useful in palaeoclimatic reconstruction than previously thought. [ABSTRACT FROM AUTHOR]

Lichenometric evidence and Schmidt hammer R-values are used to date Holocene moraine sequences in front of six high-altitude (> 1500 m) glaciers in Breheimen, central southern Norway. At three glacier forelands with southerly aspects (Høgsetbreen, Vestre Høybre and Østre Høybre), relatively small (≤ 4 m high) discrete boulder moraine ridges are shown to date from the 'Little Ice Age'. The remaining three glaciers (Østre Tundradalskyrkjabre, Nordre Tundradalskyrkjabre and Hestdalshøgdibreen), with northerly or easterly aspects and large, multiridged, rampart-like moraine complexes (15–30 m), thought to be ice-cored and of the 'push-deformation' type, lie above the local altitudinal limit of permafrost. Negatively skewed R-value distributions from these moraine complexes provide critical evidence for pre-'Little Ice Age' glacier expansion as they indicate the survival of long-weathered boulders on moraine surfaces where late-lying snow may reduce or prevent lichen growth. Formation of the moraine complexes appears to have begun in Preboreal times, most likely during the Erdalen Event, but much of their present character was determined by repeated Neoglacial glacier expansion, moraine deformation and ridge formation in the late Holocene, culminating in the 'Little Ice Age' readvance. [ABSTRACT FROM AUTHOR]

This study attempts to reconstruct the Holocene glacier history of Breheimen, southern Norway from four stream-bank mire sites and a downstream lake sediment core near Sota Sæter, based on lithostratigraphy, sediment properties (loss-on-ignition (LOI), magnetic susceptibility (MS), grain size characteristics) and 69 radiocarbon dates. Late-Preboreal deglaciation is indicated by lake-floor accumulation of organic matter (gyttja) largely replacing minerogenic sediment before 9000 cal. BP. A distinct minerogenic layer is thought to represent glacier expansion during the 8.2 ka Finse Event. Following this event until c. 2200 cal. BP, glaciers were mostly smaller than today, indicated by slow accumulation of mainly gyttja with predominantly thin minerogenic layers. A trough in LOI and corresponding small peaks in different silt fractions indicate possible glacial expansion from c. 3500 to 3000 cal. BP. The shorter c. 7500 year stream-bank mire record suggests brief, distinct episodes of Neoglacial glacier activity at c. 5600 and 3650 cal. BP. After c. 2200 cal. BP, up to three possible glacier expansion events are indicated in the lake core compared with up to eight represented in the mire sequences, suggesting greater sensitivity of the latter to small-scale glacier expansion. Marked 'suppressed' Neoglacial expansion until after c. 2200 cal. BP contrasts with the more typically reported start at 6000-5300 cal. BP elsewhere in southern Norway. Methodological implications are discussed including: factors responsible for erroneous radiocarbon dates in mire and lake core stratigraphies; high spatial variability in mire stratigraphy; determining the amplitude of glacier contraction episodes; isolating the glacial signal from background ‘noise’; and further improvement of dating. [ABSTRACT FROM AUTHOR]