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Glacial landscapes preserve records of past climate change. Investigating the glacier–climate system over the Late Quaternary provides information about past climate change and context for present‐day glacier response to climate warming. Using 28 beryllium‐10 (10Be) surface exposure dates and snowline reconstructions, we present glacier fluctuations and climate changes for the Antarctic Cold Reversal in the Ahuriri River catchment, Southern Alps of New Zealand (44°7′50″S, 169°38′29″E). Prominent terminal and lateral moraine features from the upper right tributary of the Ahuriri River valley have exposure ages of 14.5 ± 0.3, 13.6 ± 0.3 and 12.6 ± 0.2 ka, suggesting retreat of the glacier during the Antarctic Cold Reversal. Maximum elevation of lateral moraines (MELM) and accumulation area ratio (AAR) suggest snowline elevations at these ages were ≤700, ≤630 and ~360 m lower than today, respectively. This equates to air temperatures ≤3.9, ≤3.5 and 2.3 ± 0.7 °C lower than today (1981–2010), assuming no changes in past precipitation. Ice‐sculpted bedrock surfaces bound by a lateral moraine at nearby Canyon Creek have an age of 13.1 ± 0.3 ka, indicating the moraine correlates with those in the Ahuriri upper right tributary. MELM and AAR reconstructions from the Canyon Creek suggest that snowline elevations at 14.5–13.6 ka were ≤500 or ~380 m lower than today, corresponding to air temperatures ≤2.8 or 2.4 ± 0.7 °C lower than the present‐day (1981–2010). Our results provide insight into the structure of the Antarctic Cold Reversal in the Southern Alps, showing that the largest glacier advance occurred at the start of this interval at c. 14.5 ± 0.3 ka and was followed by gradual retreat. We hypothesize that the early cooling and glacier readvance in New Zealand at the onset of the Antarctic Cold Reversal were triggered by a latitudinal shift of the Southern Hemisphere westerly wind belt. [ABSTRACT FROM AUTHOR]

Quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo-glacier extent, character and behaviour, and hence past global and local glacier forcings. However, in the southern hemisphere and especially in New Zealand, the Quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties. In this study, a 1 m digital elevation model (DEM) was generated from airborne LiDAR data and supplemented with aerial imagery and field observations to analyse the exceptionally well-preserved glacial geomorphology surrounding Lake Tekapo, New Zealand. We describe a rich suite of Last Glacial Maximum (LGM) and recessional ice-marginal, subglacial, supraglacial, glaciofluvial and glaciolacustrine landform assemblages. These represent two landsystems comprising i) fluted till surfaces with low-relief push moraine ridges; and ii) crevasse-squeeze ridges, 'zig-zag' eskers and attenuated lineations. The former landsystem records the behaviour of an active temperate glacier and the latter landsystem, which is superimposed upon and inset within the former, strongly suggests intermittent surge phases. The two landsystem signatures indicate a sequential change in ice-marginal dynamics during recession that was likely to have been partially non-climatically driven. Overall, we present the first evidence of surge-type glacier behaviour in New Zealand. • LiDAR topographic data used to identify glacial landforms in New Zealand • Landform assemblages indicative of landsystem superimposition • Overall active temperate glacier recession punctuated by intermittent surge phases • First evidence of surge-type glacier behaviour in New Zealand • Changes in ice-marginal dynamics partially non-climatically driven [ABSTRACT FROM AUTHOR]

The thermal structures of eruption-fed, subglacial volcaniclastic deposits are poorly understood because their emplacement is hazardous to observe or obscured by the glacier. Determining deposit emplacement temperature, however, supports improved understanding of the flow dynamics and emplacement processes of volcaniclastic material beneath a glacier. Understanding the emplacement temperatures of ancient volcanic deposits is also important because they can be used, in combination with field studies, to infer the eruptive environment. Here, we use paleomagnetic techniques to quantify the emplacement temperatures of two ancient, proximal, eruption-fed density current deposits at Tongariro volcano, New Zealand. Stepwise thermal demagnetisation of lithic and recycled juvenile block-sized clasts reveal randomly orientated directions of magnetisation, suggesting that the clasts were rotated within the flow but not heated. Additional data from thermomagnetic, hysteresis, and isothermal remanent magnetisation tests indicate that the principal carrier of magnetic remanence is magnetite, and that the magnetisation directions are a primary remanence rather than post-depositional chemical remanent magnetisations. Following systematic removal of any viscous remanent magnetisation, the post-emplacement equilibrium temperatures for the deposits can be estimated at <150 °C. The paleomagnetic data support field evidence for rapid cooling of clasts and waterlain deposition. The deposit-forming eruptions took place beneath a summit glacier where the freshly erupted tephra was efficiently cooled by mixing with meltwater. Lithic blocks and recycled juvenile bombs were entrained and remobilised within the cool currents that drained along meltwater channels beneath the ice. This is the first study in which paleomagnetic data have been used to determine the equilibrium temperatures of subglacial density current deposits. The data provide new insight into volcaniclastic flow dynamics beneath a glacier and current-meltwater interactions. • Eruption-fed, volcaniclastic flow deposits emplaced at <150 °C. • Magnetic stability tests rule out chemical remanence magnetisation. • Deposition from tephra-laden meltwater currents that drained beneath a glacier. • First use of paleomagnetic techniques for glaciovolcanic deposits. [ABSTRACT FROM AUTHOR]

We present a 3D reconstruction of ice thickness distribution across the New Zealand Southern Alps at the Last Glacial Maximum (LGM, c. 30–18 ka). To achieve this, we used a perfect plasticity model which could easily be applied to other regions, hereafter termed REVOLTA (Reconstruction of Volume and Topography Automation). REVOLTA is driven by a Digital Elevation Model (DEM), which was modified to best represent LGM bed topography. Specifically, we removed contemporary ice, integrated offshore bathymetry and removed contemporary lakes. A review of valley in-fill sediments, uplift and denudation was also undertaken. Down-valley ice extents were constrained to an updated geo-database of LGM ice limits, whilst the model was tuned to best-fit known vertical limits from geomorphological and geochronological dating studies. We estimate a total LGM ice volume of 6,800 km3, characterised predominantly by valley style glaciation but with an ice cap across Fiordland. With a contemporary ice volume of approximately 50 km3, this represents a loss of 99.25% since the LGM. Using the newly created ice surface, equilibrium line altitudes (ELAs) for each glacier were reconstructed, revealing an average ELA depression of approximately 950 m from present. Analysis of the spatial variation of glacier-specific ELAs and their depression relative to today shows that whilst an east-west ELA gradient existed during the LGM it was less pronounced than at present. The reduced ELA gradient is attributed to an overall weakening of westerlies, a conclusion consistent with those derived from the latest independent climate models. • LGM ice thickness reconstructed on a glacier-by-glacier basis, driven by geomorphological evidence. • During the LGM the Southern Alps contained approximately 6,800 km3 ice, of which 99.25% has subsequently been lost. • Predominant valley style of glaciation across Southern Alps but ice cap across Fiordland. • The spatial patterns of precipitation and temperature were markedly different at the LGM compared to present. • Westerly circulation was apparently reduced during the LGM when compared to present. [ABSTRACT FROM AUTHOR]

Numerical glacier models applied to moraine chronologies provide an opportunity to quantify past climate change. Here we apply a two-dimensional coupled mass balance – ice flow model to well-dated moraine sequences deposited by former alpine glaciers at two central Patagonian sites: Cerro Riñón (43.97°S, 71.64°W) and Río Tranquilo (47.50°S, 72.38°W), to reconstruct the local temperatures during both the Antarctic Cold Reversal (14.7–13 ka) and the Younger Dryas (12.9–11 ka). Modelled temperature anomalies during the Antarctic Cold Reversal are −2.6 ± 0.4 °C at 44°S, and −2.9 ± 0.6 °C at 47°S. At both locations this cold event is followed by temperature increases of +0.6–0.7 °C or precipitation reductions of c. 20% to drive glacier retreat to moraines deposited during Younger Dryas time. The consistent climatic anomalies between these two latitudes suggest this region of Patagonia was responding to a common climatic event. Further, the late-glacial temperature anomalies found here compare well to those determined by similar glacier modelling techniques in New Zealand, at 43–44° S. These results support a trans-Pacific response throughout the southern mid to high latitudes (43–47° S) during the ACR that is best explained by a northward expansion of the south westerly winds. • Glacier modelling reconstructs Patagonian temperatures during late-glacial. • Cooling of −2.7 to −2.9 ° C below modern during the Antarctic Cold Reversal. • Warming of +0.6 ° C from the Antarctic Cold Reversal into the Younger Dryas period. • Climate trends parallel New Zealand glaciers implicating southern westerly winds. [ABSTRACT FROM AUTHOR]

The largest accelerations of glaciers and ice sheets are caused by changes in basal slip. Here we examine glacier speed and rain-induced accelerations using a near-continuous 26-month-long GNSS time series from a large maritime glacier (Tasman Glacier, New Zealand). During periods of high rain-rate we observe short-term increases in 24-hour speeds to up to 15-times background speed. Speeds calculated over 3-hour intervals increase to up to 36-times background speed. Acceleration events correspond with times when bed separation also increases rapidly indicating that the acceleration is associated with the growth of water-filled cavities at the bed. Glacier speeds then decrease prior to the reduction in bed separation, indicating cavity growth, not cavity extent, controls the acceleration. The short-term accelerations are superimposed on longer-term periods of enhanced velocity that persist for days to weeks and decay at similar rates to bed separation estimates and proglacial lake levels. A power-law relationship between observed rain-rate and speed exists at the glacier front and exhibits no apparent upper bound. Overall, we estimate that rain-induced accelerations account for 11–14% of Tasman Glacier's displacement during the observation period. The rain-rate–velocity relationship and the rainfall record since 2001 indicate that rain-induced speed-up events result in interannual variability in glacier displacement of 2%–13%. [ABSTRACT FROM AUTHOR]

Abstract: Determining whether glaciers registered the classic Last Glacial Maximum (LGM; ∼26,500–∼19,000 yrs ago) coevally between the hemispheres can help to discriminate among hypothesized drivers of ice-age climate. Here, we present a record of glacier behavior from the Southern Alps of New Zealand during the ‘local LGM’ (LLGM). We used 10Be surface-exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well-preserved terminal moraines deposited during the LLGM near Lake Ohau on central South Island. We then used a glaciological model to estimate a LLGM glacier snowline and atmospheric temperature from the Ohau glacier record. Seventy-three 10Be surface-exposure ages place culminations of terminal moraine construction, and hence completions of glacier advances to positions outboard of present-day Lake Ohau, at 138,600 ± 10,600 yrs, 32,520 ± 970 yrs ago, 27,400 ± 1300 yrs ago, 22,510 ± 660 yrs ago, and 18,220 ± 500 yrs ago. Recessional moraines document glacier recession into the Lake Ohau trough by 17,690 ± 350 yrs ago. Exposure of an ice-molded bedrock bench located inboard of the innermost LLGM moraines by 17,380 ± 510 yrs ago indicates that the ice tongue had receded about 40% of its overall length by that time. Comparing our chronology with distances of retreat suggests that the Ohau glacier terminus receded at a mean net rate of about 77 m yr−1 and its surface lowered by 200 m between 17,690 and 17,380 yrs ago. A long-term continuation of ice retreat in the Ohau glacier catchment is implied by moraine records at the head of Irishman Stream valley, a tributary of the Ohau glacier valley. The Irishman Stream cirque glacier advanced to produce a set of Lateglacial moraines at 13,000 ± 500 yrs ago, implying that the cirque glacier was less extensive prior to that advance. We employed a glaciological model, fit to these mapped and dated LLGM moraines, to derive snowline elevations and temperature parameters from the Ohau glacier record. The modeling experiments indicate that a snowline lowering of 920 ± 50 m and temperature depression of 6.25 ± 0.5 °C below modern values allows for the Ohau glacier to grow to an equilibrium position within the LGM moraine belt. Taken together with a glaciological simulation reported from the Irishman Stream valley, snowlines and temperatures increased by at least ∼520 m and ∼3.6 °C, respectively, between ∼18,000 and ∼13,000 yrs ago. Climate parameters derived from the Ohau glacier reconstruction are similar to those derived from glacier records from Patagonia, to air temperature indicators from Antarctica, as well as to sea-surface temperature and stratification signatures of the Southern Ocean. We think that the best explanation for the observed southern LLGM is that southern winter duration modulated Southern Ocean sea ice, which in turn influenced Southern Ocean stratification and made the surface ocean cooler. Orbitally induced cooling of the Southern Ocean provides an explanation for the LLGM in the Southern Alps having been coincident with the northern LGM. We argue further that the global effect of North Atlantic stadials led to disturbance of Southern Ocean stratification, southward shifts of the subtropical front, and retreat of Southern Alps glaciers. Collapse of Southern Ocean stratification during Heinrich Stadial-1, along with attendant sea-surface warming, triggered the onset of the Last Glacial termination in the Southern Alps of New Zealand. [Copyright &y& Elsevier]

Abstract: We present a simulation of the New Zealand Southern Alps icefield at the Last Glacial Maximum (LGM, c. 30,000–20,000 calendar years ago (ka)) in an attempt to constrain the climate of that period. We use a 500 m-resolution ice-sheet model parameterised using empirical glaciological, climatological and geological data specific to the model domain to simulate the entire Southern Alps icefield. We find that an LGM cooling of at least 6–6.5 °C is necessary to bring about valley glaciers that extend beyond the mountains. However, climate–topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain, and in order to remain within geologically reconstructed LGM limits we find that the LGM cooling was most likely associated with a precipitation regime up to 25% drier than today. Wetter-than-present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence. These results perhaps indicate that either the westerly air masses affecting New Zealand during the LGM were drier than today, or that they were weaker or zonally displaced with respect to present. [Copyright &y& Elsevier]

The article discusses a study of basal melt in high-precipitation temperate glaciers at Franz Josef Glacier in New Zealand. The geothermal and frictional heat-induced basal melt was calculated using realistic estimates of parameters for the glacier. The basal shear stress and basal speed have emerged as the most sensitive parameters in geothermal and frictional heat-induced basal melt, based on sensitivity analyses. It mentions the role of rainfall and surface melt in the production of heat dissipation within water. The importance of including ablation in the subglacial zone in temperate glaciers to arrive at an accurate mass-balance ablation measurements on high-precipitation is emphasized.

The article focuses on a study on the multispectral glacier mapping methods and the changes in the glacier area in the central Southern Alps, New Zealand from 1978 to 2002. It is said that glaciers serve as indicators of climate change, adding that regular inventories are vital in determining the global and local patterns of climate change and in managing water resources. Classification methods used in the study are band ratio, normalized-difference snow index and supervised classification. Results showed a decrease in total glacier area from 513 kilometers (km)² to 428 km² in which decline has been greater on the eastern side of the Main Divide and greater area losses among large glaciers as compared to small, high-altitude glaciers.

Glacial outburst floods or ‘jökulhlaups’ are a key part of deglaciation of both alpine mountains and of ice sheet margins. They produce widespread and intense landscape change through erosion and deposition and are a hazard to populations and infrastructure. This article reviews these aspects with an emphasis on the current ‘state of play’ of research on the phenomena. Three case studies are presented: the 2010 Eyafjallajökull and 2007 Mt Ruapehu events, and the recent jökulhlaups in western Greenland. These illustrate that, where there is sufficient lead-in time for the development of projects, the application of modern technology and of multi-disciplinary research teams enables unprecedented acquisition quality, resolution and extent of data to be gained. These exciting data should enable development of new insights towards jökulhlaup impacts and flow phenomena. [ABSTRACT FROM AUTHOR]

The article presents a study on the glacier basal velocities in the central Southern Alps of New Zealand. It discusses the methodology using orthorectification, co-registration and correlation technique to analyze the changes in glaciers between 2002 and 2006. It considers the results on changes in the Foz and Franz Joseph Glaciers compared with the debris-covered Tasman Glacier. It explores the significance of the research in understanding the behaviours of glaciers in advance/retreat cycles as a response to climate change.

This paper describes the structural glaciology of the lower Fox Glacier, a 12.7 km-long valley glacier draining the western side of the Southern Alps, New Zealand. Field data are combined with analysis of aerial photographs to present a structural interpretation of a 5 km-long segment covering the lower trunk of the glacier, from the upper icefall down-glacier to the terminus. The glacier typifies the structural patterns observed in many other alpine glaciers, including: primary stratification visible within crevasse walls in the lower icefall; foliation visible in crevasses below the lower icefall; a complex set of intersecting crevasse traces; splaying and chevron crevasses at the glacier margins; transverse crevasses forming due to longitudinal extension; longitudinal crevasses due to lateral extension near the snout; and, arcuate up-glacier dipping structures between the foot of the lower icefall and the terminus. The latter are interpreted as crevasse traces that have been reactivated as thrust faults, accommodating longitudinal compression at the glacier snout. Weak band-ogives are visible below the upper icefall, and these could be formed by multiple shearing zones uplifting basal ice to the glacier surface to produce the darker bands, rather than by discrete fault planes. Many structures such as crevasses traces do not show a clear relationship with measured surface strain-rates, in which case they may be 'close to crevassing', or are undergoing passive transport down-glacier. [ABSTRACT FROM AUTHOR]

Abstract: New Zealand glaciers reached their last glacial maximum position at or before ~25ka, and, as early as 23ka, commenced a slow and continual retreat. New cosmogenic exposure ages and field mapping from the Rakaia Valley in the South Island suggest that extensive ice survived well into the latter half of the Last Glacial–Interglacial Transition (18–11ka), with the post-15ka period inferred to have near Holocene climate conditions based on ecological proxy data. By as late as ~15.5ka, glacier termini had retreated as little as 5–10km from glacial maximum positions. Numerous minor ice still-stand positions and oscillations are recognized, but the record specifically excludes evidence for either a major climatic amelioration at ~15–16ka or a significant glacial re-advance during the Antarctic Cold Reversal (ACR) or the Younger Dryas (YD). We conclude that the currently widespread interpretation of an episodic New Zealand glacial record since the LGM is an artifact of valley-dependent retreat processes. Pro-glacial lake formation and local site conditions combined to give an apparent, but misleading, picture of glacial retreat punctuated by major, climatically driven, re-advances. [ABSTRACT FROM AUTHOR]

The origin of two ridges on the eastern slopes of Mt Allen, southern Stewart Island, has remained equivocal, with differences of opinion over the exact process-mechanisms of formation. A variety of approaches was used to test a number of possible hypotheses about the origin of the ridges. These include topographic and spatial positioning, geomorphology, sedimentology and palaeoclimatological extrapolations to reconstruct two small former cirque glaciers with equilibrium line altitudes (ELAs) of c. 600 m. It would appear the two ridges reflect a glacial origin, the glaciers interpreted as forming during the Last Glacial Maximum (LGM) in New Zealand. Whilst glaciation during this time (18–19 ka) was extensive in the Southern Alps, the restricted nature of glaciation on Mt Allen suggests the low altitude restricted glaciation to niche sites on the lee side of upland areas. [ABSTRACT FROM AUTHOR]

Abstract: A key problem in understanding valley evolution in alpine landscapes has been the lack of an independent timescale against which to measure morphological change. Here, we outline that by using space as a proxy for time, the role of glaciation in producing ‘classic’ U-shaped valleys can be quantified. The Two Thumb Range in New Zealand''s central Southern Alps is undergoing rapid tectonic transport and uplift as it is advected towards the Alpine Fault. Repeated cycles of glacial erosion during the Quaternary have fashioned an alpine landscape in the north of the range, close to the Main Divide and Alpine Fault, while valleys in the less glaciated south of the range have rounded divides and convex fluvial cross-profiles. Using known rates of tectonic transport and uplift of the Southern Alps, coupled with an offshore oxygen isotope (δ 18O) record from the Chatham Rise and glacio-geological reconstructions, time constraints can be applied to the erosional development of valleys. It is possible to estimate the duration of glacial occupancy of valleys in the Two Thumb Range, and the pattern is one of very limited glaciation of the southern valleys, with glacial occupancy increasing northwards. The key trend identifiable is that valley cross-profiles become U-shaped with c. 400–600 kyr of glacial occupancy. Other models have shown a “flattening” of valley long-profiles with increased glaciation, implying glaciers erode larger volumes of rock from mountains than rivers. From a cross-profile perspective, the simple change in geometry from V- to U-shape concurs with these models. Indeed, the transition from V- to U-shape with increasing relief and glaciation indicates glaciers may erode greater volumes of rock from mountain belts than rivers. [Copyright &y& Elsevier]

Advance and retreat of temperate glaciers is largely controlled by changes in temperature and precipitation, but the relative importance of these drivers is debated. Numerical modeling of a New Zealand glacier reveals that temperature is the dominant control on glacier length. We find that a glacial advance, dated to ca. 13,000 yr B.P., requires a cooling event of 3-4 °C. This mid-latitude Southern Hemisphere cooling is similar in magnitude to the Antarctic Cold Reversal in the Vostok ice core record and likely to be a response to the same climate signal. [ABSTRACT FROM AUTHOR]

The research aim is to reconstruct last glacial maximum (LGM) and Holocene vegetation history and ecology from fossil beetle assemblages. The LGM and Holocene sites are located in the Awatere Valley, which lies in the tectonically active Marlborough Region in the north east of the South Island of New Zealand. Beetle fossils were extracted from silty organic sediment using the standard kerosene flotation method. Fossils were identified by comparisons made to modern species based on morphology and surface features. The ecology and distribution of modern analogues are extrapolated to reconstruct the fossil environment. One hundred and forty-five beetle species belonging to 33 families were identified. The LGM fossil fauna showed the local vegetation was characterized by a forest patch surrounded by an open tussock/grassland landscape. This Nothofagus (southern beech) forest persisted at the site until mid-Holocene when it was replaced by a podocarp forest that contained high beetle diversity. Herbivores dominate in the early stage of this zone, indicating a relatively new forest environment. Later in the Holocene, the fauna is dominated by detritivores indicating an older more established forest. The late Holocene is characterized by low diversity and the absence of forest species. This fauna indicates that by 500 years ago, the forest was absent and is associated with an almost compete loss of beetle biodiversity. The fossil beetles provide a unique perspective into the past environment in the Awatere Valley on a local scale. The reconstruction supports regional pollen interpretations of Holocene vegetation by identifying a specific forest patch. Fossil beetles are thus a valuable local proxy for vegetation reconstructions. [ABSTRACT FROM AUTHOR]