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The stable oxygen (δ18Oshell) and carbon (δ13Cshell) isotope ratios retrieved from the carbonate shell of terrestrial gastropods can be used as an environmental proxy and are thought to reflect dietary composition and ambient climatic conditions (e.g. precipitation amount, humidity, temperature). Here, we generate high‐resolution isotopic profiles of nine modern land snails of the genus Placostylus, collected from two locations in New Caledonia and one location in New Zealand. We found that snails from New Zealand had, on average, higher δ18Oshell values than their counterparts in New Caledonia, which surprisingly runs counter to the expected relationship based on the isotopic composition of rainwater between these two regions. Specimens from New Caledonia exhibit ephemeral decreases in their δ18Oshell values, which could be linked to extreme precipitation events in this region, while snails from New Zealand have less variation in their δ18Oshell values. Snails from New Zealand had, on average, slightly higher δ13Cshell than their counterparts in New Caledonia, but a large difference in carbon isotopes was sometimes observed between snails collected at the same location. Most snails exhibit a temporal trend in their δ13Cshell values, indicating potential shifts in diet through to maturity. [ABSTRACT FROM AUTHOR]

Weather types (WTs) are often used to assess the relationships between synoptic‐scale atmospheric dynamics and local scale climate anomalies. We focus here on Aotearoa New Zealand (ANZ) where pre‐existing WTs have recently been characterized using a set of descriptors monitoring the daily location and intensity of their main atmospheric centres of action (ACAs). We show here that the precipitation and temperature anomalies associated with the WTs in ANZ are more complex than previously thought. They do not solely depend on type occurrence, but are also strongly modulated by within‐type changes in the location and intensity of ACAs, and their interaction with surface terrain. Thus, the mere analysis of WT occurrence is not sufficient to explain climate variability over ANZ. The magnitude and sign of daily minimum and maximum temperature anomalies are strongly driven by meridional advection of temperature, which is also driven by within‐type changes in ACAs. The amplitude of precipitation anomalies is likewise strongly variable within WTs. Associated mechanisms involve interactions between the underlying terrain and atmospheric fluxes modulated by ACAs, modifying the strength and location of orographic uplift. Finally, daily extreme precipitation can occur under several cyclonic WTs, more particularly when their low‐pressure ACAs are significantly more intense than normal. This situation is associated with more intense moisture transport towards ANZ, promoting heavy precipitation there. These results provide a detailed assessment of within‐type variability in temperature and precipitation patterns at both synoptic and local scales. They also help to improve understanding of local effects of larger scale synoptic patterns, thereby allowing for more accurate use of analogues in forecasting. [ABSTRACT FROM AUTHOR]

Mountain glaciers are highly sensitive to climate change. However, the extent to which glaciers capture regional to hemisphere‐scale atmospheric processes remains uncertain, hindering paleoclimatic interpretations derived from moraine‐based glacier reconstructions. Here, we evaluate how mid‐latitude glacier systems monitor climate by comparing climate reanalysis products with glacier annual equilibrium line altitude (ELA) elevations from the antipodal Southern Alps of New Zealand and European Alps. We find significant regional and hemispheric correlations between glacier annual ELA and summer tropospheric temperatures. Annual ELA also exhibit positive correlations with the latitude of the westerly jets in both hemispheres. These results indicate that westerly wind‐belt latitude modulates the proportion of cold versus warm air masses influencing these glacier systems. These results highlight the sensitivity of mid‐latitude glaciers to atmospheric temperatures and circulation, with implications for interpreting moraine‐based paleoclimate reconstructions. Combined impacts of ongoing tropospheric warming and poleward‐shifting westerlies will likely accelerate recession of mid‐latitude glaciers. Plain Language Summary: Mountain glaciers respond to climate change by gaining mass when the climate cools and losing mass when the climate warms. However, the extent to which these glacial fluctuations are reflective of local, regional, and hemispheric climate variations is less clear, hindering climatic interpretation of paleo‐glacier reconstructions developed from glacial landforms. This study evaluates the climatic footprint monitored by antipodal mid‐latitude glacier populations by comparing gridded reconstructions of global temperature and wind changes with glacier annual snowline elevations in the Southern Alps of New Zealand and annual equilibrium line altitude elevations in the European Alps. Our results indicate that (a) these glacier systems co‐vary with atmospheric temperatures on regional and even hemispheric scales throughout all levels of the troposphere, and (b) the latitudes of the westerly wind belts are important for regulating the proportion of cold versus warm air masses influencing glacier mass‐balance. Altogether, our results indicate that mid‐latitude mountain glacier fluctuations reflect temperature changes integrated over large regions of the atmosphere. With ongoing climate change, the combination of global atmospheric warming and poleward‐shifting westerlies is likely to accelerate recession of mid‐latitude glaciers in both hemispheres. Key Points: Mid‐latitude glacier annual equilibrium line altitude corresponds to broad regions of atmospheric temperatureMid‐latitude glacier annual equilibrium line altitude is sensitive to latitudinal shifts of the mid‐latitude westerliesThe influence of the westerlies on glaciers has important implications for interpreting past and predicting future climate change [ABSTRACT FROM AUTHOR]

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.

Non-annually resolved palaeoclimate records in the Australasian region were compiled to facilitate investigations of decadal to centennial climate variability over the past 2000 years. A total of 675 lake and wetland, geomorphic, marine, and speleothem records were identified. The majority of records are located near population centres in southeast Australia, in New Zealand, and across the maritime continent, and there are few records from the arid regions of central and western Australia. Each record was assessed against a set of a priori criteria based on temporal resolution, record length, dating methods, and confidence in the proxy–climate relationship over the Common Era. A subset of 22 records met the criteria and were endorsed for subsequent analyses. Chronological uncertainty was the primary reason why records did not meet the selection criteria. New chronologies based on Bayesian techniques were constructed for the high-quality subset to ensure a consistent approach to age modelling and quantification of age uncertainties. The primary reasons for differences between published and reconstructed age–depth models were the consideration of the non-singular distribution of ages in calibrated 14C dates and the use of estimated autocorrelation between sampled depths as a constraint for changes in accumulation rate. Existing proxies and reconstruction techniques that successfully capture climate variability in the region show potential to address spatial gaps and expand the range of climate variables covering the last 2000 years in the Australasian region. Future palaeoclimate research and records in Australasia could be greatly improved through three main actions: (i) greater data availability through the public archiving of published records; (ii) thorough characterisation of proxy–climate relationships through site monitoring and climate sensitivity tests; and (iii) improvement of chronologies through core-top dating, inclusion of tephra layers where possible, and increased date density during the Common Era.

A challenge for testing mechanisms of past climate change is the precise correlation of palaeoclimate records. Here, through climate modelling and the alignment of terrestrial, ice and marine 14C and 10Be records, the authors show that Southern Ocean freshwater hosing can trigger global change.

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.

Weather regimes (WRs), also known as synoptic types, are defined as recurrent patterns that have been used to categorize variability in atmospheric circulation. However, defining the optimal number of patterns can often be arbitrary, and there are common shortcomings when oversimplifying a wide range of synoptic conditions and weather outcomes. We build on previous work that has defined regional WRs and objectively ascribe an optimal number of once-daily weather patterns for Aotearoa New Zealand (ANZ) using affinity propagation combined with K-means clustering. Nine primary WRs for ANZ were classified based on once-daily geopotential height spatial patterns, but these patterns still retained a wide degree of spatial variability. Subsidiary clusters were subsequently defined within each primary WR by applying affinity propagation and K-means clustering to reveal the largest within-cluster differences based on joint daily temperature and precipitation anomalies. Up to three subsidiary patterns in each of the primary regimes were revealed, with a total of 21 unique daily patterns emerging from the two-tier classification. Subsidiary WRs reveal subtle differences in the location and intensity of regional-scale pressure anomalies, pressure gradients, and wind flow over both main islands that lead to large differences in surface weather anomalies. Impacts of atmospheric variability related to each subsidiary WR are exemplified by different spatial outcomes for rainfall and temperature (including intensity of anomalies) at regional and subregional levels. The approach presented in this study has utility for enhancing prediction of weather outcomes, including extreme weather, and can also be applied more widely over a range of time scales to improve understanding of weather and climate linkages. [ABSTRACT FROM AUTHOR]

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.

Reverend Richard Davis (1790–1863) was a colonial-era missionary stationed in the Far North of New Zealand who was a key figure in the early efforts of the Church Mission Society. He kept meticulous meteorological records for the early settlements of Waimate North and Kaikohe, and his observations are preserved in a two-volume set in the Sir George Grey Special Collections in the Auckland Central Library. The Davis diary volumes are significant because they constitute some of the earliest land-based meteorological measurements that were continually chronicled for New Zealand. The diary measurements cover nine years within the 1839–1851 time span that are broken into two parts: 1839–1844 and 1848–1851. Davis' meteorological recordings include daily 9 a.m. and noon temperatures and midday pressure measurements. Qualitative comments in the diary note prevailing wind flow, wind strength, cloud cover, climate variability impacts, bio-indicators suggestive of drought, and notes on extreme weather events. "Dirty weather" comments scattered throughout the diary describe disturbed conditions with strong winds and driving rainfall. The Davis diary entries coincide with the end of the Little Ice Age (LIA) and they indicate southerly and westerly circulation influences and cooler winter temperatures were more frequent than today. A comparison of climate field reconstructions derived from the Davis diary data and tree-ring-based winter temperature reconstructions are supported by tropical coral palaeotemperature evidence. Davis' pressure measurements were corroborated using ship log data from vessels associated with iconic Antarctic exploration voyages that were anchored in the Bay of Islands, and suggest the pressure series he recorded are robust and can be used as "station data". The Reverend Davis meteorological data are expected to make a significant contribution to the Atmospheric Circulation Reconstructions across the Earth (ACRE) project, which feeds the major data requirements for the longest historical reanalysis – the 20th Century Reanalysis Project (20CR). Thus these new data will help extend surface pressure-based reanalysis reconstructions of past weather covering New Zealand within the data-sparse Southern Hemisphere.

We re-evaluated speleothem isotope series from Aotearoa New Zealand that were recently contributed to the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. COnstructing Proxy Records from Age Models (COPRA) software was used to produce Bayesian age models for those speleothems. The new age modelling helped us examine Late Quaternary temporal coverage for the national speleothem network, and also supported our exploration of three different isotope master record generation techniques using Holocene δ18O data from Waitomo. We then applied the output from one of the isotope master record techniques to test an application case of how climate transfer functions can be developed using climate model simulated temperatures. Our results suggest Holocene δ18O trends at Waitomo capture air temperature variations weighted toward the primary season of soil moisture (and epikarst) recharge during winter. This interpretation is consistent with the latest monitoring data from the Waitomo region. Holocene δ18O millennial-scale trends and centennial-scale variability at Waitomo likely reflect atmospheric circulation patterns that concomitantly vary with surface water temperature and the isotopic composition of the Tasman Sea. A climate model simulation context for the Holocene millennial-scale trends in the Waitomo δ18O isotope master record suggest that site is sensitive to changes in the subtropical front (STF) and the Tasman Front. Our comparison of isotope master record techniques using Waitomo δ18O data indicate that caution is needed prior to merging δ18O data series from different caves in order to avoid time series artefacts. Future work should incorporate more high-resolution cave monitoring and climate calibration studies, and develop new speleothem data from northern and eastern regions of the country.

Te Otukapuarangi (the Pink Terrace), Te Tarata (the White Terrace) and Te Ngāwhā a Te Tuhi (the Black Terrace) were massive siliceous sinter formations at Lake Rotomahana, New Zealand, that were ostensibly lost in the catastrophic 1886 Tarawera eruption. Previous work using an unpublished watercolor map and notes by Ferdinand von Hochstetter (b. 1829–d. 1884) has recently supported claims that the former Pink and White Terraces survived the 1886 eruption, and that they may be located under tephra adjacent to the modern lake margin. Divergent perspectives about the fate of Lake Rotomahana's former sinter terraces suggest the reconstruction of New Zealand's largest historic volcanic eruption is incomplete. The undervalued approach of pairing modern geomorphic techniques with extant historic resources and geophysical data can help resolve this controversy. We harnessed a wider amount of unique historic data recorded during Hochstetter's (1859) survey than previously reported to locate the sites of Lake Rotomahana's former sinter terraces. Volcanic landforms, the physical geography of the countryside, and former settlements are tied together via common sightings between sequential survey datums. Light detection and ranging (LIDAR) data supported the reconstruction of Hochstetter's (1859) survey. Of significance, shared landmarks between the survey stations increased the confidence for resecting the 1859 datum position on the southern margin of former Lake Rotomahana. Hochstetter's survey watercolor maps are part of a series drafted prior to a final version being professionally printed, and they do not portray a spatially accurate depiction of how sinter terraces and geothermal features around former Lake Rotomahana were arranged. As such, assertions of their superior cartographic nature are not well-founded, and application of them to provide former Terrace locations is compromised. The published pre-eruption map of Lake Rotomahana validates well against Hochstetter's field diary measurements. When Hochstetter's published map is orientated using reconstructed survey datum positions at Lake Rotomahana, the former locations of the White and Pink Terraces lie entirely within the modern boundaries of the lake and not on land. The Black Terrace may have been destroyed and/or converted to an eruption crater, but may still exist on land (intact or in-part) west of Lake Rotomahana's modern shoreline. This study demonstrates the value of historic cartography to improve understanding of volcanic processes, and the potential to apply similar approaches to volcanic environments elsewhere that hold a range of pre-instrumental observations.

An end of summer snowline (EOSS) photographic dataset for Aotearoa New Zealand contains over four decades of equilibrium line altitude (ELA) observations for more than 50 index glaciers. This dataset provides an opportunity to create a climatological ELA reference series that has several applications. Our work screened out EOSS sites that had low temporal coverage and also removed limited observations when the official survey did not take place. Snowline data from 41 of 50 glaciers in the EOSS dataset were retained and included in a normalised master snowline series that spans 1977–2020. Application of the regionally representative normalised master snowline series in monthly and seasonally resolved climate response function analyses showed consistently strong relationships with austral warm-season temperatures for land-based stations west of the Southern Alps and the central Tasman Sea. There is a trend towards higher regional snowlines since the 1990s that has been steepening in recent decades. If contemporary decadal normalised master snowline series trends are maintained, the average Southern Alps snowline elevation will be displaced at least 200 m higher than normal by the 2025–2034 decade. More frequent extremely high snowlines are expected to drive more extreme cumulative mass-balance losses that will reduce the glacierised area of Aotearoa New Zealand. [ABSTRACT FROM AUTHOR]