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Karst geology is characterized by the presence of sinkholes and voids, which may pose significant risk to existing infrastructure. Sinkhole formation is often observed near active quarries, where dewatering operations can alter regional groundwater flow patterns leading to subsidence and increased void formation. In these areas, identifying locations which may be susceptible to sinkhole formation requires an ability to map dissolution features within the rock. Traditional geotechnical explorations alone are not well-suited to this effort as they only provide subsurface information at discrete points and therefore may miss voids within the rock. Geophysical methods offer a means to produce continuous profiles of the rock surface and possible locations for voids but interpreting the results of these tests in karstic geology can be challenging. This study uses 2D electrical resistivity and seismic surveys at a site with previous sinkhole activity along an interstate in central Alabama. The site is adjacent to a limestone quarry. Resistivity data is collected using 2D dipole-dipole and strong-gradient arrays. The seismic data is processed using a full waveform inversion (FWI) technique. Subsurface profiles interpreted from the geophysical surveys are then compared to borehole data from previous site investigations. Results from the geophysical surveys are found to be consistent with borehole data regarding variation of bedrock depth and identification of possible sinkhole features. Potential limitations and sources of error pertaining to each survey type are considered.

Fox Glacier/Te Moeka o Tuawe is a fast-responding maritime glacier that has undergone multiple advance and retreat phases during recent decades. Here we use a combination of repeat photography, Str...

Glaciers are unique indicators of climate change. While recent global-scale glacier decline has been attributed to anthropogenic forcing, direct links between human-induced climate warming and extreme glacier mass-loss years have not been documented. Here we apply event attribution methods to document this at the regional scale, targeting the highest mass-loss years (2011 and 2018) across New Zealand’s Southern Alps. Glacier mass balance is simulated using temperature and precipitation from multiple climate model ensembles. We estimate extreme mass loss was at least six times (2011) and ten times (2018) (>90% confidence) more likely to occur with anthropogenic forcing than without. This increased likelihood is driven by present-day temperatures ~1.0 °C above the pre-industrial average, confirming a connection between anthropogenic emissions and high annual ice loss. These results suggest that as warming and extreme heat events continue and intensify, there will be an increasingly visible human fingerprint on extreme glacier mass-loss years in the coming decades. Detecting a human role in a given year of extreme glacier mass loss is difficult at regional scales. Event attribution methods estimate that two extreme mass-loss years in the New Zealand Southern Alps, 2011 and 2018, were at least six and ten times more likely with anthropogenic climate warming.

The land ice contribution to global mean sea level rise has not yet been predicted 1 using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models 2–8, but primarily used previous-generation scenarios 9 and climate models 10, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios 11,12 using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.

Mountain glacier moraine sequences and their chronologies allow us to evaluate the timing and climate conditions that underpin changes in the equilibrium line altitudes (ELAs), which can provide valuable information on the paleoclimatology of understudied regions such as tropical East Africa. However, moraine sequences are inherently discontinuous, and the precise climate conditions that they represent can be ambiguous due to the sensitivity of mountain glaciers to temperature, precipitation, and other environmental variables. Here, we used a two-dimensional (2-D) ice-flow and mass-balance model to simulate glacier extents and ELAs in the Rwenzori Mountains in East Africa over the past 31,000 yr (31 k.y.), including the Last Glacial Maximum (LGM), late glacial period, and the Holocene Epoch. We drove the glacier model with two independent, continuous temperature reconstructions to simulate possible glacier length changes through time. Model input paleoclimate values came from branched glycerol dialkyl glycerol tetraether (brGDGT) temperature reconstructions from alpine lakes on Mount Kenya for the last ~31 k.y., and precipitation reconstructions for the LGM came from various East African locations. We then compared the simulated fluctuations with the positions and ages (where known) of the Rwenzori moraines. The simulated glacier extents reached within 1.1 km of the dated LGM moraines in one valley (93% of the full LGM extent) when forced by the brGDGT temperature reconstructions (maximum cooling of 6.1 °C) and a decrease in precipitation (−10% than modern amounts). These simulations suggest that the Rwenzori glaciers required a cooling of at least 6.1 °C to reach the dated LGM moraines. Based on the model output, we predict an age of 12–11 ka for moraines located halfway between the LGM and modern glacier extents. We also predict ice-free conditions in the Rwenzori Mountains for most of the early to middle Holocene, followed by a late Holocene glacier readvance within the last 2000 yr.

The only complete inventory of New Zealand glaciers was based on aerial photography starting in 1978. While there have been partial updates using 2002 and 2009 satellite data, most glaciers are still represented by the 1978 outlines in contemporary global glacier databases. The objective of this project is to establish an updated glacier inventory for New Zealand. We have used Landsat 8 OLI satellite imagery from February and March 2016 for delineating clean glaciers using a semi-automatic band ratio method and debris-covered glaciers using a maximum likelihood classification. The outlines have been checked against Sentinel-2 MSI data, which have a higher resolution. Manual post processing was necessary due to misclassifications (e.g. lakes, clouds), mapping in shadowed areas, and combining the clean and debris-covered parts into single glaciers. New Zealand glaciers cover an area of 794 ± 34 km2 in 2016 with a debris-covered area of 10%. Of the 2918 glaciers, seven glaciers are >10 km2 while 71% is 2. The debris cover on those largest glaciers is >40%. Only 15 glaciers are located on the North Island. For a selection of glaciers, we were able to calculate the area reduction between the 1978 and 2016 inventories.

Glacier mass loss is recognized as a significant contributor to current sea-level rise. However, large uncertainties remain in projections of glacier mass loss on global and regional scales. We present an ensemble of 279 global-scale glacier mass and area change projections for the 21st century based on eleven glacier models using up to ten General Circulation Models (GCMs) and four Representative Concentration Pathways (RCPs) as boundary conditions. We partition the total uncertainty into the individual contributions caused by glacier models, GCMs, RCPs, and natural variability. We find that emission scenario uncertainty is growing throughout the 21st century, and is the largest source of uncertainty by 2100. The relative importance of glacier model uncertainty decreases over time, but it is the greatest source of uncertainty until the middle of this century. The projection uncertainty associated with natural variability is small on the global scale but has strong effects on small regional scales. The projected global mass loss by 2100 relative to 2015 (75±64 mm sea-level equivalent (SLE) for RCP2.6, 165±98 mm SLE for RCP8.5) is lower than, but within the uncertainty range of previous projections.

Mountain glacier records offer important constraints on the timing and magnitude of climate variability during the last glacial cycle. Existing moraine chronologies from the central Southern Alps indicate maximum ice extent was achieved during marine isotope stages 3–4, followed by repeated advances of similar, but gradually declining extent during marine isotope stage 2, until onset of the glacial termination. Questions remain over the precise role of climate in driving these changes, as most existing moraine chronologies come from large, complex former valley glacier systems, where non-climatic influences such as changing bed topography and proglacial lake formation may have influenced glacier length changes. Here we address this problem via a new cosmogenic 10Be chronology and equilibrium line altitude reconstruction from a cirque glacier situated in Fiordland, New Zealand. Our chronology shows moraine deposition at 32 ± 11 ka, 18.7 ± 0.2 ka, 18.1 ± 0.1 ka, and c. 17.2 ± 0.3 ka. The simple geometry of the former glacier supports the role of climate in driving a net decline of regional ice volume during marine isotope stages 3–2. Close spacing and good preservation of the 19–17 ka moraines permits 2D glacier reconstruction which suggests the equilibrium line altitude remained depressed by c.1130 m (equivalent to 5.8 ± 0.6 °C colder than present) during this interval. Onset of warming after 17.2 ± 0.2 ka is consistent with climate proxy evidence for a sustained southward shift in the southern westerly winds, which may have promoted deglaciation via shifting ocean currents and promoting increases in atmospheric carbon dioxide.

Glaciers will lose mass during the next decades as the climate warms. While the largest uncertainty in this mass loss is the global greenhouse gas emissions pathway, on a local or regional scale there are large uncertainties in some processes that influence glacier response. We explore the competing processes of reduced ablation under debris cover and increased ablation from calving by applying a coupled mass-balance/ice-flow model in the central Southern Alps/Kā Tiritiri o te Moana of New Zealand. Glacier volume loss is assessed over the period from AD 1880 to AD 2099, driven by observed climate data before 2005, and perturbing the modern climate state and imposing representative concentration pathway (RCP) scenarios 2.6–8.5 as expressed by six global circulation models (GCMs) which leads to a regional warming of between 1–4 °C (2006–2099). Key findings are (1) modelled ice volume reduced from 47 km3 to 29 km3 between AD 1880 and 2005; (2) over the period 2006–2099 further volume loss to 24 km3 (19% reduction) is committed under present-day climate; (3) modelled ice volume at AD 2099 is estimated at 2 km3 ± 6 km3 (RCP8.5) to 15 km3 ± 6 km3 (RCP2.6), a reduction of 50–92% relative to present day. The wide range of projected ice volumes reflects the large range of temperature projections between RCP2.6 and RCP8.5. The mode and timing of ice loss provides insight into processes that will drive future glacier behavior. Under RCP2.6 at 2099, the glaciers retain a similar configuration to present, although clean-ice glaciers will retreat significantly, and some debris-covered tongues will disconnect from their accumulation areas. For RCP4.5, RCP6.0 and RCP8.5 the clean-ice glaciers will retreat to become small remnants in the high mountains. Experiments where the debris cover is removed shows a much faster loss of ice, whereas experiments with no lake calving slows ice loss. However, under all but the most moderate warming scenarios, by 2099 the strong climatic forcing overwhelms these processes as there is little ice left at low elevations where debris cover and lake calving occur.

Geological climate archives from the Holocene Epoch provide baseline information concerning natural climate variability. Temperate mountain glacier extent is sensitive to summer air temperature, thus geological records of past glacier length changes are a useful proxy for this climatic variable. Here we present a new cosmogenic 10Be chronology of glacier length changes at Dart Glacier in the Southern Alps, New Zealand. Prominent moraines deposited 321 ± 44 yr ago (n = 11) and 7.8 ± 0.3 ka (n = 5) show glaciers during the Little Ice Age were less extensive than during the early Holocene. This pattern of net Holocene glacier retreat is consistent with emerging data from other catchments in New Zealand and across the southern mid-latitudes. Using the physical framework of a transient global climate model simulation, we suggest that cool summers in the early Holocene were promoted by the local summer insolation minimum, together with low atmospheric greenhouse gas concentrations, causing an early Holocene austral glacial maximum. An insolation-driven reduction in seasonality at southern mid-latitudes may reconcile differences between early Holocene temperature reconstructions where climate proxies have different seasonal sensitivities. We suggest that rising greenhouse gas concentrations after 7 ka caused regional-scale glacier retreat and appear to be the dominant driver of multi-millennial summer temperature trends in the southern mid-latitudes during the present interglacial.

Quantifying historic changes in glacier size and mass balance is important for understanding how the cryosphere responds to climate variability and change. Airborne photogrammetry enables glacier extent and equilibrium line altitudes (ELAs) to be monitored for more glaciers at lower cost than traditional mass-balance programs and other remote-sensing techniques. Since 1977, end-of-summer-snowlines, which are a proxy for annual ELAs, have been recorded for 50 glaciers in the Southern Alps of New Zealand using oblique aerial photographs. In this study, we use structure from motion photogrammetry to estimate the camera parameters, including position, for historic photographs, which we then use to measure glacier change. We apply this method to a small maritime New Zealand glacier (Brewster Glacier, 1670–2400 m a.s.l.) to derive annual ELA and length records between 1981 and 2017, and quantify the uncertainties associated with the method. Our length reconstruction shows largely continuous terminus retreat of 365 ± 12 m for Brewster Glacier since 1981. The ELA record, which compares well with glaciological mass-balance data measured between 2005 and 2015, shows pronounced interannual variability. Mean ELAs range from 1707 ± 6 to 2303 ± 5 m a.s.l., with the highest ELAs occurring in the last decade.

Glaciers offer the potential to reconstruct past climate over timescales from decades to millennia. They are found on nearly every continent, and at the Last Glacial Maximum, glaciers were larger in all regions on Earth. The physics of glacier-climate interaction are relatively well understood, and glacier models can be used to reconstruct past climate from geological evidence of past glacier extent. This can lead to significant insights regarding past, present, and future climate. For example, glacier modeling has demonstrated that the near-ubiquitous global pattern of glacier retreat during the last few centuries resulted from a global-scale climate warming of ∼1°C, consistent with instrumental data and climate proxy records. Climate reconstructions from glaciers have also demonstrated that the tropics were colder at the Last Glacial Maximum than was originally inferred from sea surface temperature reconstructions. Future efforts to reconstruct climate from glaciers may provide new constraints on climate sensitivity to CO2 forcing, polar amplification of climate change, and more.

Recent model studies suggest that interannual climatic variability could be confounding the interpretation of glacier fluctuations as climate signals. Paleoclimate interpretations of moraine positions and associated cosmogenic exposure ages may have large uncertainties if the glacier in question was sensitive to interannual variability. Here we address the potential for interannual temperature and precipitation variability to cause large shifts in glacier length during the Holocene. Using a coupled ice-flow and mass-balance model, we simulate the response of Cameron Glacier, a small mountain glacier in New Zealand's Southern Alps, to two types of climate forcing: equilibrium climate and variable climate. Our equilibrium results suggest a net warming trend from the Early Holocene ( 10.69 ± 0.41 ka; 2.7 °C cooler than present) to the Late Holocene (CE 1864; 1.3 °C cooler than present). Interannual climatic variability cannot account for the Holocene glacier fluctuations in this valley. Future studies should consider local environmental characteristics, such as a glacier's climatic setting and topography, to determine the magnitude of glacier length changes caused by interannual variability.

Glaciers experienced worldwide retreat during the twentieth and early twenty first centuries, and the negative trend in global glacier mass balance since the early 1990s is predominantly a response to anthropogenic climate warming. The exceptional terminus advance of some glaciers during recent global warming is thought to relate to locally specific climate conditions, such as increased precipitation. In New Zealand, at least 58 glaciers advanced between 1983 and 2008, and Franz Josef and Fox glaciers advanced nearly continuously during this time. Here we show that the glacier advance phase resulted predominantly from discrete periods of reduced air temperature, rather than increased precipitation. The lower temperatures were associated with anomalous southerly winds and low sea surface temperature in the Tasman Sea region. These conditions result from variability in the structure of the extratropical atmospheric circulation over the South Pacific. While this sequence of climate variability and its effect on New Zealand glaciers is unusual on a global scale, it remains consistent with a climate system that is being modified by humans., Many New Zealand glaciers advanced during recent global warming, bucking a worldwide trend of glacier retreat. Here, the authors show that these glacier advances were forced by a sequence of unusually cool years in the New Zealand region, rather than a period of increased precipitation.

Estimating sediment deposition in a stream, a standard procedure for dealing with aggradation problem is complicated in an ungauged catchment due to the absence of necessary flow data. A serious aggradation problem within an ungauged catchment in Alabama, USA, blocked the conveyance of a bridge, reducing the clearance under the bridge from several feet to a couple of inches. A study of historical aerial imageries showed deforestation in the catchment by a significant amount over a period consistent with the first identification of the problem. To further diagnose the aggradation problem, due to the lack of any gauging stations, local rainfall, flow, and sediment measurements were attempted. However, due to the difficulty of installing an area-velocity sensor in an actively aggrading stream, the parameter transfer process for a hydrologic model was adopted to understand/estimate streamflow. Simulated discharge combined with erosion parameters of MUSLE (modified universal soil loss equation) helped in the estimation of sediment yield of the catchment. Sediment yield for the catchment showed a significant increase in recent years. A two-dimensional hydraulic model was developed at the bridge site to examine potential engineering strategies to wash sediments off and mitigate further aggradation. This study is to quantify the increase of sediment yield in an ungauged catchment due to land cover changes and other contributing factors and develop strategies and recommendations for preventing future aggradation in the vicinity of the bridge.

Recognising the scarcity of glacier mass-balance data in the Southern Hemisphere, a mass-balance measurement programme was started at Brewster Glacier in the Southern Alps of New Zealand in 2004. Evolution of the measurement regime over the 11 years of data recorded means there are differences in the spatial density of data obtained. To ensure the temporal integrity of the dataset a new geostatistical approach is developed to calculate mass balance. Spatial co-variance between elevation and snow depth allows a digital elevation model to be used in a co-kriging approach to develop a snow depth index (SDI). By capturing the observed spatial variability in snow depth, the SDI is a more reliable predictor than elevation and is used to adjust each year of measurements consistently despite variability in sampling spatial density. The SDI also resolves the spatial structure of summer balance better than elevation. Co-kriging is used again to spatially interpolate a derived mean summer balance index using SDI as a co-variate, which yields a spatial predictor for summer balance. The average glacier-wide surface winter, summer and annual balances over the period 2005–15 are 2484, −2586 and −102 mm w.e., respectively, with changes in summer balance explaining most of the variability in annual balance.

Geological records of mountain glacier fluctuations provide useful evidence for tracing the magnitude and rate of past temperature change. In this study, we present air temperature reconstructions for the last glacial termination in New Zealand derived using snowline reconstructions and numerical glacier modelling. We target the Arthur's Pass moraines in the Otira River catchment, which have previously been dated to the Lateglacial using cosmogenic 10Be. Recalculation of these exposure ages using a locally calibrated 10Be production rate indicates that these moraines formed ca. 16–14 ka. Our glacier modelling experiments and snowline reconstructions exhibit good agreement and show that the Arthur's Pass moraines formed in a climate that was 2.2–3.5 °C colder than present. Combining our results with other, proximal glacier records shows that ice in this catchment retreated ca. 50 km from the coastal plain to the main divide during the interval 17–15 ka, in response to a temperature increase of at least ca. 3 °C. Over half of this retreat occurred after the glacier had withdrawn from an overdeepened basin. Thus, we conclude that temperature increase was the primary driver of widespread and rapid glacier retreat in New Zealand at the onset of the last glacial termination.

Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers, constrained by moraine mapping, afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2-D coupled energy balance–ice flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7 °C, if precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The majority of catchments targeted require temperature decreases of 5.1 to 6.3 °C to simulate the former glaciers, which represents our best estimate of the temperature anomaly in the central North Island, New Zealand, during the Last Glacial Maximum. A decrease in precipitation of up to 25 % from present, as suggested by proxy evidence and climate models, increases the magnitude of the required temperature changes by up to 0.8 °C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial (

Daily time lapse imagery and pixel tracking was used to monitor and track spatial and temporal changes in sediment-mantled hillslopes, during and immediately after glacier retreat in the Fox Glacier/Te Moeka o Tuawe valley, New Zealand. Observations from 2014 to 2018 of the Fox Glacier and surrounding hillslopes show hillslope failure is primarily coincident with, and triggered by, glacier retreat with rainfall accelerating movement of the hillslope. During glacier retreat, failure of the hillslope primarily occurred through sediment sliding, internal deformation of the sediment and occasional surficial debris falls, flows and avalanches delivering approximately 9.2 M m3 of sediment directly to the underside of the glacier over the study period with a maximum daily averaged movement of 0.4 m per day of the main sediment mass. Following debuttressing, hillslope failure became dominated by localised rainfall-induced debris flows which initiated gullying of the sediment-mantled slope. Ongoing instability of the slope and associated movement is maintained by toe erosion from the Fox River and melting dead ice, while continued rapid failure is facilitated through localised debris flows. The tracking of temporal and spatial changes of sediment-mantled hillslopes during glacier retreat has shown broad-scale hillslope response to occur quickly within days of rainfall or accelerated glacier retreat, particularly during summer. Debris flows, commonly thought to be a dominant erosion process within paraglacial environments, only occur following complete debuttressing and are supply-limited, only occurring after sediment sliding has occurred. Unlike many other case studies, sediment connectivity immediately following glacier retreat is high due to a lack of storage space and high rainfall inducing mass movements, efficiently delivering hillslope sediments to the proglacial stream channel. Attempts to quantify displaced volumes of sediment from paraglacial systems are likely underestimated due to a) a lack of focus on the early and latter stages of debuttressing b) a reliance on debris flows being a primary transport mechanism, and c) sediment being delivered sub-glacially rather than supra-glacially, further enhancing connectivity.

Glacier behaviour during the mid-Holocene (MH, 6000 years BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeoclimate signals. In this study we examine the climatic forcing of glacier response in the MH by evaluating modelled glacier equilibrium line altitudes (ELAs) and climatic conditions during the MH compared with pre-industrial time (PI, year 1750). We focus on the middle latitudes of the Southern Hemisphere, specifically Patagonia and the South Island of New Zealand. Climate conditions for the MH were obtained from PMIP2 model simulations, which in turn were used to force a simple glacier mass balance model to simulate changes in ELA. In Patagonia, the models simulate colder conditions during the MH in austral summer (−0.2 °C), autumn (−0.5 °C), and winter (−0.4), and warmer temperatures (0.2 °C) during spring. In the Southern Alps the models show colder MH conditions in autumn (−0.7 °C) and winter (−0.4 °C), warmer conditions in spring (0.3 °C), and no significant change in summer temperature. Precipitation does not show significant changes but exhibits a seasonal shift, with less precipitation from April to September and more precipitation from October to April during the MH in both regions. The mass balance model simulates a climatic ELA that is 15–33 m lower during the MH compared with PI conditions. We suggest that the main causes of this difference are driven mainly by colder temperatures associated with the MH simulation. Differences in temperature have a dual effect on glacier mass balance: (i) less energy is available for ablation during summer and early autumn and (ii) lower temperatures cause more precipitation to fall as snow rather than rain in late autumn and winter, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed by 6000 years BP in South America and New Zealand.

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%.

Glacier mass balance is more sensitive to warming than cooling, but feedbacks related to the exposure of previously buried firn and ice in very warm years is not generally considered in sensitivity...

Short-term glacier velocity variations typically occur when a water input is accommodated by an increase in the subglacial water pressure. Although these velocity variations have been well documented on many glaciers, few studies have considered them on glaciers where heavy rain and glacier melt occur year-round. This study investigates the relationship between water inputs and glacier velocity on Franz Josef Glacier, New Zealand. We installed six GNSS stations across the lower glacier during austral summer 2010/11 and one station during summer 2012/13. Glacier velocity remained elevated at all stations for ∼7 days following large rain events. During diurnal melt events, we find velocity variations in the early afternoon (12:00–16:00) at 600 m a.s.l. and in the late evening (20:00–01:00) at 400 m a.s.l. We hypothesize that the late-evening velocity variations occurred as an upstream region of high subglacial water pressures and accelerated ice motion propagated downstream. This mechanism may also explain the increased longitudinal compression and transverse extension across the lower glacier during speed-up events. Our results indicate that the subglacial drainage system likely decreases in efficiency upstream and that the water input variability can still cause short-term velocity variations despite the large year-round water inputs.

The Darwin–Hatherton Glacial system (DHGS) connects the East Antarctic Ice Sheet (EAIS) with the Ross Ice Shelf and is a key area for understanding past variations in ice thickness of surrounding ice masses. Here we present the first detailed measurements of ice thickness and grounding zone characteristics of the DHGS as well as new measurements of ice velocity. The results illustrate the changes that occur in glacier geometry and ice flux as ice flows from the polar plateau and into the Ross Ice Shelf. The ice discharge and the mean basal ice shelf melt for the first 8.5 km downstream of the grounding line amount to 0.24 ± 0.05 km3 a−1 and 0.3 ± 0.1 m a−1, respectively. As the ice begins to float, ice thickness decreases rapidly and basal terraces develop. Constructed maps of glacier geometry suggest that ice drainage from the EAIS into the Darwin Glacier occurs primarily through a deep subglacial canyon. By contrast, ice thins to

Ka Roimata o Hine Hukatere (Franz Josef Glacier) is a fast-flowing maritime glacier and its climatological and hydrological drivers are different from those of many previously studied alpine glaciers. The glacier tongue has recently advanced as well as retreated, remains largely snow free, has significant volumes of melt and rainwater inputs throughout the year, and experiences small radiation and air temperature fluctuations over diurnal to seasonal time scales. We discuss measurements of surface velocity made between 2000 and 2012 at annual, seasonal, weekly, and daily time scales together with measurements of glacier geometry change, and calculations of surface water inputs and subglacial water pressure variations derived from a distributed surface mass balance model and a one-dimensional conduit hydrology model, respectively. Annual velocity variations are linked to changes in glacier geometry and advance/retreat cycles with accelerations during thickening and advance and decelerations during...

Compilation of modern and historical length change records for Franz Josef and Fox Glaciers demonstrates that these glaciers have lost ~ 3 km in length and at least 3–4 km 2 in area since the 1800s, with the greatest overall loss occurring between 1934 and 1983. Within this dramatic and ongoing retreat, both glaciers have experienced periods of re-advance. The record from Franz Josef Glacier is the most detailed, and shows major advances from 1946 to 1951 (340 m), 1965–1967 (400 m), 1983–1999 (1420 m) and 2004–2008 (280 m). At Fox Glacier the record is similar, with advances recorded during 1964–1968 (60 m), 1985–1999 (710 m) and 2004–2008 (290 m). Apart from the latest advance event, the magnitude of advance has been greater at Franz Josef Glacier, suggesting a higher length sensitivity. Analysis of the relationship between glacier length and a reconstructed annual equilibrium line altitude (ELA) record shows that the glaciers react very quickly to ELA variations — with the greatest correlation at 3–4 years' lag. The present (2014) retreat is the fastest retreat in the records of both glaciers. While decadal length fluctuations have been linked to hemispheric ocean–atmosphere variability, the overall reduction in length is a clear sign of twentieth century warming. However, documenting glacier length changes can be challenging; especially when increased surface debris-cover makes identification of the ‘true’ terminus a convoluted process.

Climate proxy records from the middle to high latitude Southern Hemisphere indicate that a Lateglacial (15,000–11,500 years ago) climate reversal, approximately coeval with the Antarctic Cold Reversal (ACR), interrupted a warming trend during deglaciation. In New Zealand, some palaeoclimate proxy records indicate a cool episode during the ACR (ca 14,500–12,500 years ago), while others do not express a significant change in climate. Recently published moraine maps and ages present an opportunity to improve the palaeoclimate interpretation through numerical modelling of glaciers. We use a coupled energy-balance and ice-flow model to quantify palaeoclimate from past glacier extent constrained by mapped and dated moraines in the headwaters of Irishman Stream, a high-elevation catchment in the Southern Alps. First, a suite of steady-state model runs is used to identify the temperature and precipitation forcing required to fit the modelled glacier to well-dated Lateglacial moraine crests. Second, time-dependent glacier simulations forced by a nearby proxy temperature record derived from chironomids are used to assess the fit with the glacial geomorphic record. Steady-state experiments using an optimal parameter set demonstrate that the conditions under which the 13,000 year old moraine formed were 2.3–3.2 °C colder than present with the range in temperature corresponding to a ±20% variance in precipitation relative to the present-day. This reconstructed climate change relative to the present-day corresponds to an equilibrium-line altitude of ca 2000 ± 40 m above sea level (asl), which is ca 400 m lower than present. Time-dependent simulations of glacier length produce ice advance to within 100 m of the 13,000 year old terminal moraine, indicating that the chironomid-based temperature forcing and moraine record provide consistent information about past climate. Our results, together with other climate proxy reconstructions from pollen records and marine sediment cores, support the notion that temperatures during the ACR in New Zealand were ∼2–3 °C cooler than today.

The timing and magnitude of postglacial climatic changes around the globe provide insights into the underlying drivers of natural climate change. Using geomorphologic mapping of moraines, 10 Be surface-exposure dating, snowline reconstructions, and numerical modeling, we quantified glacier behavior during Late Glacial (15–11.5 ka) and Holocene (the past ∼11.5 k.y.) time in the Ben Ohau Range, New Zealand. Glaciers were more extensive during the Antarctic Cold Reversal (ACR), than subsequently, and the margins underwent a punctuated net withdrawal over the Holocene. Numerical modeling experiments that achieve the best fit to the moraines suggest that air temperature during the ACR was between 1.8 °C and 2.6 °C cooler than today, with similar (±20%) prescribed precipitation. After the ACR, a net snowline rise of ∼100 m through the Younger Dryas stadial (12.9–11.7 ka) was succeeded by a further "long-term," or net, rise of ∼100 m between ∼11 k.y. and ∼500 yr ago. Glacier snowline records in New Zealand show generally coherent Late Glacial and Holocene climate trends. However, the paleoclimate record in the southwest Pacific region shows important differences from that in the Northern Hemisphere.

Snow distribution patterns are still poorly understood in steep alpine catchments because of mass redistribution from wind and avalanching. Snow models rarely operate with sufficient resolution, physics or input data to resolve this issue explicitly, and existing sub-grid parameterisations are rarely tested in this type of terrain. To address this issue daily snow cover observations, obtained from a ground-based camera, are combined with a snow melt model to estimate the spatial distribution of snow water equivalent (SWE) in a mountainous alpine catchment. Results show the importance of slope in controlling the spatial distribution of SWE and snow duration. This distribution is linked to the physical process of gravitational transport, where there is removal of snow from steep slopes and preferential deposition on moderate-angle slopes. From a modelling perspective, if sub-grid snow variability is parameterised using a log-normal probability distribution (as is common in hydrological and land-use models) then ignoring steep/shallow slope differences leads to an overestimation of melt at the beginning of the melt season, and a premature end to the snow melt season. When modelling SWE in complex terrain, care should be taken to consider reduced SWE on steep slopes.

Type 1 Diabetes (T1D) is a chronic pro-inflammatory autoimmune disease consisting of islet-infiltrating leukocytes involved in pancreatic β-cell lysis. One promising treatment for T1D is islet transplantation; however, clinical application is constrained due to limited islet availability, adverse effects of immunosuppressants, and declining graft survival. Islet encapsulation may provide an immunoprotective barrier to preserve islet function and prevent immune-mediated rejection after transplantation. We previously demonstrated that a novel cytoprotective nanothin multilayer coating for islet encapsulation consisting of tannic acid (TA), an immunomodulatory antioxidant, and poly(N-vinylpyrrolidone) (PVPON), was efficacious in dampening in vitro immune responses involved in transplant rejection and preserving in vitro islet function. However, the ability of (PVPON/TA) to maintain islet function in vivo and reverse diabetes has not been tested. Recent evidence has demonstrated that modulation of redox status can affect pro-inflammatory immune responses. Therefore, we hypothesized that transplanted (PVPON/TA)-encapsulated islets can restore euglycemia to diabetic mice and provide an immunoprotective barrier. Our results demonstrate that (PVPON/TA) nanothin coatings can significantly decrease in vitro chemokine synthesis and diabetogenic T cell migration. Importantly, (PVPON/TA)-encapsulated islets restored euglycemia after transplantation into diabetic mice. Our results demonstrate that (PVPON/TA)-encapsulated islets may suppress immune responses and enhance islet allograft acceptance in patients with T1D.

A potential complication in using glacier extent to estimate paleoclimatic conditions is the influence of glacier bed evolution on changes in ice extent over time. Here, we examine this issue through model-based reconstructions of the Last Glacial Maximum (LGM) Pukaki glacier, Southern Alps, New Zealand, whose LGM extents are exceptionally well defined by lateral and terminal moraines. Using the well-dated moraine limits as an empirical constraint on maximum ice extents, we employ a one-dimensional glacier flowline model driven by a mass balance model in order to evaluate the influence of climate and glacier bed profile on the extent of the LGM Pukaki glacier. The LGM glacier bed is buried by Lateglacial and post-glacial sediment, so we calculate bed profiles using a modified version of the one-dimensional model and available geologic constraints. A best fit to the moraine record occurs with a LGM temperature of 7–8 °C cooler than present, with precipitation ranging from 80% to 100% of present levels. Modeling of the bed profile evolution indicates that bed changes alone could account for kilometer-scale changes in glacier width and length.

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.

Mid-latitude maritime glaciers are responding quickly and directly to climate change. This response is expected to continue, and will result in maritime glaciers making a large contribution to sea level rise over the coming decades. Maritime glaciers in the New Zealand Southern Alps provide an opportunity to learn more about climate–glacier mass balance relationships in a high precipitation setting, and how these relationships might change in the future. Ice core and direct glaciological measurements are used to construct a 24-year record of net accumulation, the longest of its type in New Zealand. We demonstrate that variations in net accumulation on Tasman Glacier are more strongly influenced by temperature than by precipitation. Further, it is temperature during the ablation season that exerts most control. Atmospheric circulation patterns, in particular the state of the El Nino Southern Oscillation (ENSO) and Southern Annular Mode (SAM), were found to influence net accumulation. When the SAM is positive and the ENSO in a La Nina phase, easterly and northerly wind anomalies are enhanced, temperatures increase in the Southern Alps region and more negative glacier mass balances result. Conversely when SAM is negative and ENSO in an El Nino phase, westerly and southerly wind anomalies occur, and temperatures decrease in the Southern Alps region. In this case, glacier mass balance is more likely to be positive. However, relationships between glacier mass balance and these atmospheric circulation modes are not simply linear, with some of the lowest net accumulation years associated with inverse polarity between the SAM and the ENSO.

Understanding relationships between snow accumulation and synoptic climatology is important for assessing the way in which future climate variability will impact on glacier mass balance. However, few studies have as yet examined these relationships. Variability in snow accumulation on mid-latitude glaciers is strongly influenced by atmospheric circulation, orography, and redistribution of snow by wind. Very little is known about these processes in the New Zealand Southern Alps, where it is assumed that west-facing glaciers receive higher snow totals. However, few measurements are available to test this hypothesis. These processes were investigated over a 21-day period in winter 2008 on glaciers located west (Franz Josef Glacier) and east (Tasman Glacier) of the Main Divide of the Southern Alps. We directly measured snow accumulation and considered how it was affected by synoptic weather regime and location with respect to the Main Divide. Both glaciers received ∼75% of their snowfall during troug...

Coverage of ice velocities in the central part of the Southern Alps, New Zealand, is obtained from feature tracking using repeat optical imagery in 2002 and 2006. Precise orthorectification, co-registration and correlation is carried out using the freely available software COSI-Corr. This analysis, combined with short times between image acquisitions, has enabled velocities to be captured even in the accumulation areas, where velocities are lowest and surface features ephemeral. The results indicate large velocities for mountain glaciers (i.e. up to ∼5 m d−1) as well as dynamic changes in some glaciers that have occurred between 2002 and 2006. For the steep and more responsive Fox and Franz Josef Glaciers the speed increased at the glacier snout during the advance period, while the low-angled and debris-covered Tasman Glacier showed no measurable velocity change. Velocity increases on the steeper glaciers are the result of an observed thickening and steepening of the glacier tongues as they moved from a retreat phase in 2002 to an advance phase in 2006. This contrasting behaviour is consistent with historic terminus position changes. The steeper glaciers have undergone several advance/retreat cycles during the observation period (1894 to present), while the low-angled glacier showed little terminus response until retreat resulting from the accelerating growth of a proglacial lake commenced in 1983.

Net accumulation measurements from two glaciers located on opposite sides of the New Zealand Southern Alps were used to explore processes controlling spatial variability. The degree of variability, as measured by the spatial variogram, differed in each of the three successive years, but the lowest variance occurred on both glaciers in March 2008, after a hot and dry summer. Strong relationships between net accumulation and elevation within the accumulation area were only found on Franz Josef Glacier (FJG), despite this being the primary control used in glacier mass balance modelling. Interaction between wind and topography was found to be important to the distribution of net accumulation on both glaciers. The crevasse stratigraphy method is an ideal way to gain good spatial coverage of net accumulation, and particularly suited to glaciers with high annual precipitation. Copyright © 2010 John Wiley & Sons, Ltd.

The sensitivity of glaciers to climatic change is key information in assessing the response and sea-level implications of projected future warming. New Zealand glaciers are important globally as an example of how maritime glaciers will contribute to sea-level rise. A spatially distributed energy-balance model is applied to Brewster Glacier, New Zealand, in order to calculate glacier mass balance, run-off and sensitivity to climate change. The model successfully simulates four annual mass-balance cycles. Close to half (52%) of the energy available for melt on the glacier is supplied by turbulent heat fluxes, with radiation less important, except during the winter. Model sensitivity to temperature change is one of the largest reported on Earth, at −2.0 m w.e. a−1 °C−1. In contrast, a 50% change in precipitation is required to offset the mass-balance change resulting from a 1 °C temperature change. Meltwater runoff sensitivity is also very high, increasing 60% with a 1°C warming. The extreme sensitivity of mass balance to temperature change suggests that significant ice loss will occur with even moderate climate warming.

Understanding the response of relatively small ice masses to climate change on a century-to-century timescale is important because of their significant contribution to sea level change in the recent past, and their likely contribution in the next century. Franz Josef Glacier, with its excellent terminus position record, location in the Southern Hemisphere, and its extreme sensitivity to climatic changes, is a key data point for understanding the magnitude and mechanisms of past and future climate changes. Here, we use a reconstructed mass balance record to drive an ice flow model which simulates the general retreat of the glacier during the 20th century. The model is then used to project future glacier variations, based on regionally downscaled climate change scenarios. The results indicate that, under a mean climate change scenario, the glacier will retreat 5 km and lose 38% of its mass by 2100. Different scenarios give a range of recession from 3.9 to 6.4 km, and a range of volume loss from 26% to 58%. On a global scale, the magnitude of the retreat is at the upper end of the range calculated for other, similar sized, glaciers.

Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (∼5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

Despite their relatively small total ice volume, mid-latitude valley glaciers are expected to make a significant contribution to global sea-level rise over the next century due to the sensitivity of their mass-balance systems to small changes in climate. Here we use a degree-day model to reconstruct the past century of mass-balance variation at ‘Ka Roimata o Hine Hukatere’ Franz Josef Glacier, New Zealand, and to predict how mass balance may change over the next century. Analysis of the relationship between temperature, precipitation and mass balance indicates that temperature is a stronger control than precipitation on the mass balance of Franz Josef Glacier. The glacier’s mass balance, relative to its 1986 geometry, has decreased at a mean annual rate of 0.02m a–1w.e. between 1894 and 2005. We compare this reduction to observations of terminus advance and retreat, of which Franz Josef Glacier has the best record in the Southern Hemisphere. For the years 2000–05 the relative mass balance ranged from –0.75 to +1.50m a–1w.e., with 2000/01 the only year showing a negative mass balance. In a regionally downscaled Intergovernmental Panel on Climate Change mean warming scenario, the annual relative mass balance will continue to decrease at 0.02m a–1w.e. through the next century.

During February and March 2003, a series of unusual events involving supraglacial flooding and ice collapse affected an area of Franz Josef Glacier, South Westland, New Zealand. This paper describes these events and examines rainfall and river stage data in order to explain their occurrence. Relationships between rainfall events, supraglacial flooding, and stage of the Waiho River suggest that subglacial water was rerouted to a supraglacial position, most likely resulting from blockage of the subglacial route by ice collapse near the base of the main icefall on the lower part of the glacier. Review of previous literature reveals that a variety of flood and ice collapse events are frequent at Franz Josef Glacier. While this is only one of several natural hazards in the Franz Josef area, it is of considerable importance because of the large number and significant duration of tourist visits to the terminus and onto the lower part of the glacier.

The late Holocene retreat of the West Antarctic ice sheet is crucial information for assessing its current dynamics. However, data from this period for parts of the ice sheet where significant change has taken place, mainly the Ross Sea, are very sparse. Some significant dated deposits are from lakes dammed by valley glaciers, themselves dammed by the Ross Ice Sheet. The least age of these deposits is somewhat later than the retreat of the Ross Ice Sheet from the locality on account of the lagged response of the glacier. We present a model of the Hatherton Glacier, which examines its relationship to the Ross ice sheet, using dated margin data from ice-dammed lakes. Problems in modelling are the coupling with the Darwin Glacier, the unknown bed topography and the poorly known surface mass balance, which include blue ice areas. We infer the bed topography by tuning a valley glacier model, and use this model to (i) estimate the thickness of the Last Glacial Maximum (LGM) Ross Ice Sheet; and (ii) estimate the response time of the Hatherton Glacier to changes in the Ross Sea ice sheet. The best fit of the glacier surface profile to the geological data occur if the LGM Ross Ice Sheet elevation is assumed to be 800 m higher than the present-day ice shelf surface. If the decay of the Ross Ice sheet is linear with time, the response time is of the order of several centuries. Step changes in the elevation of the Ross Ice Sheet lead to a response time around one thousand years. The dated deposits in the Hatherton Valley cannot be used directly as dates of Ross Ice Sheet grounding line retreat.

[1] The “mass balance sensitivity” of a glacier provides a means for assessing its response to future warming and contribution to sea level rise. Many studies have concluded that the first-order control on mass balance sensitivity is climatic, where higher-precipitation (and less continental) glaciers are most sensitive while lower-precipitation (and more continental) glaciers are least sensitive. The Southern Alps in New Zealand experience a limited range of continentality (9–13 K) but strong gradients in precipitation (2.5–11 m a−1). Using an energy balance model applied on a regional scale we find that the central Southern Alps glaciers are very sensitive to temperature change (1.9 m w.e. a−1 K−1, with a range of −1.1 to −4.0 m w.e. a−1 K−1) and that an 82% increase in precipitation is required to offset a 1 K warming. Spatial variations in mass balance sensitivity cannot be simply explained as a function of precipitation. Topographic effects are important, and we find that debris cover reduces mass balance sensitivity. Mass balance amplitude, which takes into account debris cover, hypsometry and other topographic characteristics, is a better predictor of mass balance sensitivity than precipitation. The mass balance gradient is almost as good a predictor indicating that hypsometry is not a necessary component of sensitivity calculations. Estimating mass balance sensitivity as a function of mass balance gradient allows for parameterizations of mass balance sensitivity based on glacier inventory data. This provides a simple and robust way to assess glacier mass balance sensitivity on a global scale, which may refine future predictions of valley glacier melt and its contribution to sea level rise.

[1] This paper evaluates the use of field data on the spatial variability of snow water equivalent (SWE) to guide the design of distributed snow models. An extensive reanalysis of results from previous field studies in different snow environments around the world is presented, followed by an analysis of field data on spatial variability of snow collected in the headwaters of the Jollie River basin, a rugged mountain catchment in the Southern Alps of New Zealand. In addition, area-averaged simulations of SWE based on different types of spatial discretization are evaluated. Spatial variability of SWE is shaped by a range of different processes that occur across a hierarchy of spatial scales. Spatial variability at the watershed-scale is shaped by variability in near-surface meteorological fields (e.g., elevation gradients in temperature) and, provided suitable meteorological data is available, can be explicitly resolved by spatial interpolation/extrapolation. On the other hand, spatial variability of SWE at the hillslope-scale is governed by processes such as drifting, sloughing of snow off steep slopes, trapping of snow by shrubs, and the nonuniform unloading of snow by the forest canopy, which are more difficult to resolve explicitly. Subgrid probability distributions are often capable of representing the aggregate-impact of unresolved processes at the hillslope-scale, though they may not adequately capture the effects of elevation gradients. While the best modeling strategy is case-specific, the analysis in this paper provides guidance on both the suitability of several common snow modeling approaches and on the choice of parameter values in subgrid probability distributions.

Ice-penetrating radar and modelling data are presented suggesting the presence of a zone of temperate ice, water ponding or saturated sediment beneath the tongue of Taylor Glacier, Dry Valleys, Antarctica. The proposed subglacial zone lies 3–6 km up-glacier of the terminus and is 400– 1000m across. The zone coincides with an extensive topographic overdeepening to 80m below sea level. High values of residual bed reflective power across this zone compared to other regions and the margins of the glacier require a high dielectric contrast between the ice and the bed and are strongly indicative of the presence of basal water or saturated sediment. Analysis of the hydraulic equipotential surface also indicates strong convergence into this zone of subglacial water flow paths. However, thermodynamic modelling reveals that basal temperatures in this region could not exceed –7˚C relative to the pressure-melting point. Such a result is at odds with the radar observations unless the subglacial water is a hypersaline brine.