82 research outputs found

    Meteorological data rescue: citizen science lessons learned from Southern Weather Discovery

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    Daily weather reconstructions (called "reanalyses") can help improve our understanding of meteorology and long-term climate changes. Adding undigitized historical weather observations to the datasets that underpin reanalyses is desirable; however, time requirements to capture those data from a range of archives is usually limited. Southern Weather Discovery is a citizen science data rescue project that recovered tabulated handwritten meteorological observations from ship log books and land-based stations spanning New Zealand, the Southern Ocean, and Antarctica. We describe the Zooniverse-hosted Southern Weather Discovery campaign, highlight promotion tactics, and replicate keying levels needed to obtain 100% complete transcribed datasets with minimal type 1 and type 2 transcription errors. Rescued weather observations can augment optical character recognition (OCR) text recognition libraries. Closer links between citizen science data rescue and OCR-based scientific data capture will accelerate weather reconstruction improvements, which can be harnessed to mitigate impacts on communities and infrastructure from weather extremes

    Coincident evolution of glaciers and ice-marginal proglacial lakes across the Southern Alps, New Zealand: Past, present and future

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    Global glacier mass loss is causing expansion of proglacial landscapes and producing meltwater that can become impounded as lakes within natural topographic depressions or ‘overdeepenings’. It is important to understand the evolution of these proglacial landscapes for water resources, natural hazards and ecosystem services. In this study we (i) overview contemporary loss of glacier ice across the Southern Alps of New Zealand, (ii) analyse ice-marginal lake development since the 1980s, (iii) utilise modelled glacier ice thickness to suggest the position and size of future lakes, and (iv) employ a large-scale glacier evolution model to suggest the timing of future lake formation and future lake expansion rate. In recent decades, hundreds of Southern Alps glaciers have been lost and those remaining have fragmented both by separation of tributaries and by detachment of ablation zones. Glaciers with ice-contact margins in proglacial lakes (n > 0.1 km2 = 20 in 2020) have experienced the greatest terminus retreat and typically twice as negative mass balance compared to similar-sized land-terminating glaciers. Our analysis indicates a positive relationship between mean glacier mass balance and rate of lake growth (R2 = 0.34) and also with length of an ice-contact lake boundary (R2 = 0.44). We project sustained and relatively homogenous glacier volume loss for east-draining basins but in contrast a heterogeneous pattern of volume loss for west-draining basins. Our model results show that ice-marginal lakes will increase in combined size by ~150% towards 2050 and then decrease to 2100 as glaciers disconnect from them. Overall, our findings should inform (i) glacier evolution models into which ice-marginal lake effects need incorporating, (ii) studies of rapid landscape evolution and especially of meltwater and sediment delivery, and (iii) considerations of future meltwater supply and water quality.ISSN:0921-818

    An extended last glacial maximum in the Southern Hemisphere: A contribution to the SHeMax project

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    Proxy records from across the Southern Hemisphere show significant local to regional scale variability in climatic and environmental conditions during late Marine Isotope Stage 3 and early Marine Isotope Stage 2, prior to the global last glacial maximum (LGM; 26.5–19.0 kyr). Although not necessarily synchronous across the hemisphere, the regional signature of these pre-26.5 kyr ‘events’ suggests greater complexity of events preceding the global LGM in the Southern Hemisphere than in the North. Here we explore climatic and environmental variability across the Southern Hemisphere during two time-slices: 32 ± 1 kyr (representing the period of Southern Hemisphere summer insolation minimum) and 21 ± 1 kyr (representing the period of maximum global ice volume), based on previously published palaeoclimate proxy data. Temperatures were already approaching glacial levels across the Southern Hemisphere at 32 ± 1 kyr and minimum temperatures were attained in many records at ~21 ± 1 kyr. Furthermore, the descent into minimum temperatures occurred later in Antarctica than elsewhere in the Southern Hemisphere. Effective precipitation was more variable, with evidence for both increased and decreased moisture availability across the hemisphere during each time slice. The pattern of effective precipitation indicates that local factors likely played a more significant role in driving moisture availability compared to temperature. Our findings indicate that the onset of full-glacial conditions across the Southern Hemisphere occurred prior to the attainment of global maximum ice volume

    Correlation of Glacier ELA/Snowlines & Temperature Station data with ERA5 Temperature and Wind Speed, 1979 to 2017

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    This dataset contains the gridded correlation results from a study that sought to better understand the climatic footprint monitored by antipodal mid-latitude glacier populations. Understanding the links between glaciers and climate is critical for accurately interpreting contemporary cryosphere changes, and interrogating the causes of past glacier behavior. However, work is still needed to refine the extent to which they capture regional to hemisphere-scale atmospheric processes. A Pearson's correlation was performed between yearly summer seasonal data from the ERA5 gridded reconstructions of global temperature and wind changes on each available ERA5 pressure level and yearly glacier snowline/ELA elevations in the Southern Alps of New Zealand and in the European Alps. December-Febuary austral summer data was correlated with the Southern Alps records and June-August Northern Hemisphere summer data was correlated with the European Alps. The ERA5 input dataset was regridded onto a new monthly axis representing the true month lengths. Then the weighted seasonal average (December-February and June-August) was calculated. Individuals glaciers with Equilibrium Line Altitude (ELA; European Alps) and End of Summer Snowlines (EOSS; Southern Alps) were selected with respective records covering at least 80% of the 1979-2017/15 analysis period. The records from each glacier were then standardized and an EOF analysis was performed to obtain each location's First Principle Component for input into the Pearson's Correlation. A nearly identical set of analyses was performed using weather stations temperature data instead of glacier ELA/snowlines. The New Zealand station equivalent is from the National Institute of Water and Atmospheric Research (NIWA) New Zealand seven-station (NZ7S) series. The European Alps equivalent is from the HistAlp regional weather station syntheses. This companion analysis allows the glacier's ability to record the climate to be compared to that of meteorological instruments

    Precipitation and temperature anomalies over Aotearoa New Zealand analysed by weather types and descriptors of atmospheric centres of action

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    International audienceWeather 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

    Response to comment on “A global environmental crisis 42,000 years ago”

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    Our paper about the impacts of the Laschamps Geomagnetic Excursion 42,000 years ago has provoked considerable scientific and public interest, particularly in the so-called Adams Event associated with the initial transition of the magnetic poles. Although we welcome the opportunity to discuss our new ideas, Hawks’ assertions of misrepresentation are especially disappointing given his limited examination of the material

    A global environmental crisis 42,000 years ago

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    Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record

    “Beyond Weather Regimes”: Descriptors Monitoring Atmospheric Centers of Action. A case study for Aotearoa New Zealand

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    International audienceAbstract This paper introduces a set of descriptors applied to weather regimes, that allow for a detailed monitoring of the location and intensity of their atmospheric centers of action (e.g. troughs and ridges) and the gradients between them, when applicable. Descriptors are designed to document the effect of climate variability and change in modulating the character of daily weather regimes, rather than merely their occurrence statistics. As a case study, the methodology is applied to Aotearoa New Zealand (ANZ), using ERA5 ensemble reanalysis data for the period 1979-2019. Here, we analyze teleconnections between the regimes and their descriptors, and large-scale climate variability. Results show a significant modulation of centers of action by the phase of the Southern Annular Mode, with a strong relationship identified with the latitude of atmospheric ridges. Significant associations with El Niño Southern Oscillation are also identified. Modes of large-scale variability have a stronger influence on the regimes’ intrinsic features than their occurrence. This demonstrates the usefulness of such descriptors, which help understand the relationship between mid-latitude transient perturbations and large-scale modes of climate variability. In future research, this methodological framework will be applied to analyze (i) low-frequency changes in weather regimes under climate change, in line with the southward shift of storm tracks, and (ii) regional-scale effects on the climate of ANZ, resulting from interaction with its topography
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