Distribution of Patterned Ground and Surficial Deposits on a Debris-covered Glacier Surface in Mullins Valley and Upper Beacon Valley, Antarctica

Beacon Valley is located in the western Dry Valleys, Antarctica, adjacent to the East Antarctic Ice Sheet (EAIS). The surficial material on the floor of Beacon Valley is segmented into large polygonal landforms separated by trenches. Buried beneath the polygons and surficial material is massive ground ice. One hypothesis is that the buried ice in upper Beacon Valley is glacier ice originating from local debris-covered glaciers. The networks of polygons and trenches form as the buried ice undergoes thermal contraction and sublimation. Contraction cracks that penetrate the surficial material and buried ice in Beacon Valley contain Late Miocene age volcanic ashes. The ashes postdate the buried ice. The preservation of such old ice implies a continuous extreme polar condition in Beacon Valley since late Miocene time. An alternative explanation is that the buried ice in Beacon Valley is modem ground ice that formed from percolation of melted, wind-blown snow that subsequently froze within the sediment mantle. Polygonal landforms would result from the seasonal freeze-thaw of the modem ground ice and surficial material. Continual freeze-thaw action, or cryoturbation, would create a mass of coalesced, modern ice lenses covered with older sediment. The buried ice in this case could be young, and hence could not be used to imply stable climatic conditions in Beacon Valley since the late Miocene. Polygons cover the surface of a debris-covered glacier that fills part of upper Beacon Valley and Mullins Valley. A survey of the debris-covered glacier surface indicates that polygons mature with distance from the equilibrium line. The polygon morphology highlights the transport path of the buried ice in upper Beacon Valley, which can be sourced to the cirque (accumulation zone) at the head of Mullins Valley. The buried ice in upper Beacon Valley is part of a coherent, massive ice body of glacial origin. A gray diamicton is draped over the buried ice. It has textural and weathering characteristics akin to englacial, buried ice sediment. This diamicton is classified as a till that formed from sublimation of buried ice. The sublimation till (28% sand, 69% gravel, and 3% mud) is sorted by narrow contraction cracks in the buried ice that results in sand wedge deposits (83% sand, 11% gravel, and 6% mud). The grain-sizes that comprise sublimation till and sand wedges indicate that sediment is initially derived from sublimation of the buried ice. Deep polygon trenches develop over thermal contraction cracks in the buried ice, and create traps for wind-blown sediment (reworked sublimation till, sand wedge sediment and volcanic ash.) The tops of some contraction cracks were void of sediment, indicative of a sediment starvation. In this case, any primary volcanic ashfall could descend directly into active sand wedges. As sublimation occurs, sand wedges containing volcanic ash can slump over the sublimation till and buried ice. The stratigraphy of massive weathered sand, with stringers of volcanic ash, resting on sublimation till and buried ice is widespread in upper Beacon Valley. Because the contraction cracks and sand wedges are secondary to the buried ice, the ashes contained in them can afford a minimum age for the buried ice. This study supports the concept of the ash chronology previously used (Sugden et al., 1995) to date the buried ice at late Miocene age, and argues for persistent polar conditions in Beacon Valley since that time

Towards a radiocarbon calibration for oxygen isotope stage 3 using New Zealand kauri (Agathis australis)

It is well known that radiocarbon years do not directly equate to calendar time. As a result, considerable effort has been devoted to generating a decadally resolved calibration curve for the Holocene and latter part of the last termination. A calibration curve that can be unambiguously attributed to changes in atmospheric ¹⁴C content has not, however, been generated beyond 26 kyr cal BP, despite the urgent need to rigorously test climatic, environmental, and archaeological models. Here, we discuss the potential of New Zealand kauri (Agathis australis) to define the structure of the ¹⁴C calibration curve using annually resolved tree rings and thereby provide an absolute measure of atmospheric ¹⁴C. We report bidecadally sampled ¹⁴C measurements obtained from a floating 1050-yr chronology, demonstrating repeatable ¹⁴C measurements near the present limits of the dating method. The results indicate that considerable scope exists for a high-resolution ¹⁴C calibration curve back through OIS-3 using subfossil wood from this source

Ice thickness and volume changes across the Southern Alps, New Zealand, from the little ice age to present

Rapid changes observed today in mountain glaciers need to be put into a longer-term context to understand global sea-level contributions, regional climate-glacier systems and local landscape evolution. In this study we determined volume changes for 400 mountain glaciers across the Southern Alps, New Zealand for three time periods; pre-industrial “Little Ice Age (LIA)” to 1978, 1978 to 2009 and 2009 to 2019. At least 60 km3 ± 12 km3 or between 41 and 62% of the LIA total ice volume has been lost. The rate of mass loss has nearly doubled from − 0.4 m w.e year−1 during 1,600 to 1978 to − 0.7 m w.e year−1 at present. In comparison Patagonia has lost just 11% of it’s LIA volume. Glacier ice in the Southern Alps has become restricted to higher elevations and to large debris-covered ablation tongues terminating in lakes. The accelerating rate of ice loss reflects regional-specific climate conditions and suggests that peak glacial meltwater production is imminent if not already passed, which has profound implications for water resources and riverine habitats

Locating Relict Sinter Terrace Sites at Lake Rotomahana, New Zealand, With Ferdinand von Hochstetter's Legacy Cartography, Historic Maps, and LIDAR

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

Post-translational modification directs nuclear and hyphal tip localization of Candida albicans mRNA-binding protein Slr1

The morphological transition of the opportunistic fungal pathogen Candida albicans from budding to hyphal growth has been implicated in its ability to cause disease in animal models. Absence of SR-like RNA-binding protein Slr1 slows hyphal formation and decreases virulence in a systemic candidiasis model, suggesting a role for post-transcriptional regulation in these processes. SR (serine–arginine)-rich proteins influence multiple steps in mRNA metabolism and their localization and function are frequently controlled by modification. We now demonstrate that Slr1 binds to polyadenylated RNA and that its intracellular localization is modulated by phosphorylation and methylation. Wildtype Slr1-GFP is predominantly nuclear, but also co-fractionates with translating ribosomes. The non-phosphorylatable slr1-6SA-GFP protein, in which six serines in SR/RS clusters are substituted with alanines, primarily localizes to the cytoplasm in budding cells. Intriguingly, hyphal cells display a slr1-6SA-GFP focus at the tip near the Spitzenkörper, a vesicular structure involved in molecular trafficking to the tip. The presence of slr1-6SA-GFP hyphal tip foci is reduced in the absence of the mRNA-transport protein She3, suggesting that unphosphorylated Slr1 associates with mRNA–protein complexes transported to the tip. The impact of SLR1 deletion on hyphal formation and function thus may be partially due to a role in hyphal mRNA transport

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

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

The International Surface Pressure Databank version 2

The International Surface Pressure Databank (ISPD) is the world's largest collection of global surface and sea-level pressure observations. It was developed by extracting observations from established international archives, through international cooperation with data recovery facilitated by the Atmospheric Circulation Reconstructions over the Earth (ACRE) initiative, and directly by contributing universities, organizations, and countries. The dataset period is currently 1768–2012 and consists of three data components: observations from land stations, marine observing systems, and tropical cyclone best track pressure reports. Version 2 of the ISPD (ISPDv2) was created to be observational input for the Twentieth Century Reanalysis Project (20CR) and contains the quality control and assimilation feedback metadata from the 20CR. Since then, it has been used for various general climate and weather studies, and an updated version 3 (ISPDv3) has been used in the ERA-20C reanalysis in connection with the European Reanalysis of Global Climate Observations project (ERA-CLIM). The focus of this paper is on the ISPDv2 and the inclusion of the 20CR feedback metadata. The Research Data Archive at the National Center for Atmospheric Research provides data collection and access for the ISPDv2, and will provide access to future versions

The importance and scientific value of long weather and climate records; examples of historical marine data efforts across the globe

The rescue, digitization, quality control, preservation, and utilization of long and high quality meteorological and climate records, particularly related to historical marine data, are crucial for advancing our understanding of the Earth’s climate system. In combination with land and air measurements, historical marine records serve as foundational pillars in linking present and past weather and climate information, offering essential insights into natural climate variability, extreme events in marine areas, baseline data for assessing current changes, and inputs for enhancing predictive climate models and reanalyses. This paper provides an overview of rescue activities covering marine weather data over the past centuries and presents and highlights several ongoing projects across the world and how the data are used in an integrative and international framework. Current and future continuous efforts in data rescue, digitization, quality control, and the development of temporally high-resolution meteorological and climatological observations from oceans, will greatly help to further complete our understanding and knowledge of the Earth’s climate system, including extremes, as well as improve the quality of reanalysis