This paper describes a new method for the automatic detection of pit structures in airborne laser scanning data collected with at least five emitted pulses per square metre. Oppland County, Norway, has a large number of ancient iron production sites and hunting systems. Today, these are manifested as pits in the ground. The iron production sites were used 1400–700 yr ago, and consist of charcoal burning pits, often located in groups of four around a central oven, which also occasionally can be located as a small mound. The hunting systems were used 2000–500 yr ago, and consisted of concealed pitfall traps and wooden fences, located on deer trekking routes. The fences are gone, but the pits remain. Many of the iron production sites and hunting systems are located in forested areas. The current, traditional mapping of these is relatively poor, with many individual pits missing, and poor positional accuracy of the ones that are mapped. This means that overlays of cultural heritage sites cannot be trusted when planning new highways, residential areas, cabins, etc. Experience suggests that automatic detection is clearly superior to visual inspection of the lidar data in finding small pits or pits that are not easily visible. However, visual inspection is better at finding additional information as human interpretation based on archaeological knowledge can be applied. Combining these two methods secures a very good basis for subsequent field survey. In conclusion, we demonstrate that automatic detection of hunting systems and iron extraction sites in lidar data is a valuable tool in combination with visual inspection of the lidar data, prior to field survey. Provided that the point density of the lidar data is high enough, the field survey can be accomplished ten times faster compared with the traditional approach without lidar data. Copyright © 2012 John Wiley & Sons, Ltd.

The main aim of this study is to describe consequences of climate change in the mountain region of southern Norway with respect to recently exposed finds of archaeological remains associated with reindeer hunting and trapping at and around ice patches in central southern Norway. In the early years of the twenty-first century, warm summers caused negative glacier mass balance and significant glacier retreat and melting of ice patches in central southern Norway. As a result, prehistoric remains lost and/or left by past reindeer hunters appeared at ice patches in mountain areas of southern Norway. In the warm summer and autumn of 2006 the number of artefact recoveries at ice patches increased significantly because of melting of snow and ice patches and more than 100 objects were recovered in the Oppland county alone. In 2009, detailed multidisciplinary investigations were carried out at the Juvfonne ice patch in Jotunheimen at an elevation of c. 1850 metres. A well-preserved Iron Age hunting station was discovered and in total c. 600 artefacts have been documented at the Juvfonne site alone. Most of the objects were recovered and brought to the Museum of Cultural History at the University of Oslo for conservation, exhibition and storing. Thirteen so called ‘scaring sticks’ recovered from the recently exposed foreland of Juvfonne were radiocarbon dated, yielding ages that group in two separate time intervals, ad 246–534 and ad 804–898 (±1 sigma). By putting the temporal distribution of the radiocarbon-dated artefacts into the context of late-Holocene glacier-size variations in the Jotunheimen and Jostedalsbreen regions, we conclude that the most extensive reindeer hunting and trapping associated with snow/ice patches was related to periods with prevailing warm summers when the reindeer herds gathered on high-altitude, contracted glaciers and ice patches to avoid insect plagues. The ‘freshness’ of the fragile organic finds strongly indicates that at least some of the artefacts were rapidly covered by snow and ice and that they may have been more-or-less continuously covered by snow and ice since they were first buried.

The melting of perennial ice patches globally is uncovering a fragile record of alpine activity, especially hunting and the use of mountain passes. When rescued by systematic fieldwork (glacial archaeology), this evidence opens an unprecedented window on the chronology of high-elevation activity. Recent research in Jotunheimen and surrounding mountain areas of Norway has recovered over 2000 finds—many associated with reindeer hunting (e.g. arrows). We report the radiocarbon dates of 153 objects and use a kernel density estimation (KDE) method to determine the distribution of dated events from ca 4000 BCE to the present. Interpreted in light of shifting environmental, preservation and socio-economic factors, these new data show counterintuitive trends in the intensity of reindeer hunting and other high-elevation activity. Cold temperatures may sometimes have kept humans from Norway's highest elevations, as expected based on accessibility, exposure and reindeer distributions. In times of increasing demand for mountain resources, however, activity probably continued in the face of adverse or variable climatic conditions. The use of KDE modelling makes it possible to observe this patterning without the spurious effects of noise introduced by the discrete nature of the finds and the radiocarbon calibration process.

Mountain passes have played a key role in past mobility, facilitating transhumance, intra-regional travel and long-distance exchange. Current global warming has revealed an example of such a pass at Lendbreen, Norway. Artefacts exposed by the melting ice indicate usage from c. AD 300-1500, with a peak in activity c. AD 1000 during the Viking Age-a time of increased mobility, political centralisation and growing trade and urbanisation in Northern Europe. Lendbreen provides new information concerning the socio-economic factors that influenced highelevation travel, and increases our understanding of the role of mountain passes in inter-and intraregional communication and exchange.

In the context of global warming, ice patches are increasingly important foci of high-elevation archaeology. Langfonne in Jotunheimen, central southern Norway, is uniquely suited to provide a window onto site formation processes and taphonomy in this novel archaeological setting. Here the site record from systematic survey includes the largest number of arrows, bones and antlers from a single ice patch worldwide. Combining data from these finds with the results of glaciological investigations provides an opportunity to interpret the influence of archaeological site formation processes and taphonomy on chronological and spatial patterning. It is inferred that the spatial patterning of artefacts at Langfonne is partly a result of displacement by ice movement, meltwater and other natural processes. Nevertheless, the finds yield information regarding past hunting practices and the extent of ice at different times. An early cluster of finds from c.6000 cal yr BP may result from ice deformation which has brought early objects to the surface. The number of arrows increases from c. 1700 cal yr BP onwards, peaking around c.1200 cal yr BP. Artefacts from this period show a wide spatial distribution indicating both the preferential survival of more recent finds and that they were lost when the ice patch was large. Based on comparison with the chronology of natural bone and antler samples from the site, the greater number of finds of this date may also reflect a period of increased hunting.