Total Ice Volume Research Articles

Mapping geodetically inferred Antarctic ice surface height changes into thickness changes: a sensitivity study

Abstract. Determining recent Antarctic ice volume changes from satellite altimeter measurements of ice surface height requires a correction for contemporaneous vertical crustal deformation. This correction must consider two main sources of crustal deformation: (1) ongoing glacial isostatic adjustment (GIA), that is, the deformational, gravitational, and rotational response to Late Pleistocene and Holocene ice and ocean mass changes and (2) modern ice mass change. In this study, we seek to quantify the uncertainties associated with each of these corrections. Corrections of ice surface height changes for correction 1 have generally involved the adoption of global models of GIA defined by some preferred combination of ice history and mantle viscoelastic structure. We have computed the GIA correction generated from a coupled ice sheet–sea level model and a realistic Earth model incorporating three-dimensional viscoelastic structure. Integrating the difference between this correction and those from recent GIA analyses widely adopted in the literature yields an uncertainty in total present-day ice volume change equivalent to approximately 10 % of Antarctic ice mass loss inferred for the period 2010–2020. This reinforces earlier work indicating that ice histories characterized by relatively high excess ice volume at the Last Glacial Maximum may be introducing a significant error in estimates of modern melt rates. Regarding correction 2, a spatially invariant scaling has commonly been used to convert GIA-corrected ice surface height changes obtained from satellite altimetry to ice volume estimates. We adopt modeling results based on a projection of Antarctic ice mass change over the period 2015–2055 to demonstrate a spatial variability in the scaling of up to 10 % across the ice sheet. Furthermore, using these calculations, we find a systematic error of ∼ 3 % in the projected net ice volume change, with most of the difference arising in areas of West Antarctica above mantle zones of low viscosity.

The foundations of the Patagonian icefields

The two vast Patagonian icefields are a global hotspot for ice-loss. However, not much is known about the total ice volume they store - let alone its spatial distribution. One reason is that the abundant record of direct thickness measurements has never been systematically exploited. Here, this record is combined with remotely-sensed information on past ice thickness mapped from glacier retreat. Both datasets are incorporated in a state-of-the-art, mass-conservation approach to produce a well-informed map of the basal topography beneath the icefields. Its major asset is the reliability increase of thicknesses values along the many marine- and lake-terminating glaciers. For these, frontal ice-discharge is notably lower than previously reported. This finding implies that direct climatic control was more influential for past ice loss. We redact a total volume for both icefields in 2000 of 5351 km3. Despite the wealth of observations used in this assessment, relative volume uncertainties remain elevated.

Некоторые оценки тяжелых ледовых условий (сжатий) в Печорском море по данным наблюдений и моделирования (моделирование и анализ)

The work continues the study focused on the analysis of the severe ice conditions’ formation in the Pechora Sea during navigation in 2003 and 2018 (published in vol.12, no.4, 2022). Using a numerical model, the authors reproduce the dynamics and some elements of the morphometry of the ice cover during the indicated ice seasons. Thus, they reveal that the significant ice pressure (100—150 kPa and more) is caused by the strong on-shore wind, while the ice pressure related to the tidal phenomena have the predominant value at the weak winds. The tidal ice pressure occurs permanently and regularly, and varies mainly within the range of 10—50 kPa. The contribution of ice hummocks to the total ice volume becomes significant when strong ice pressure happens at the background of high ice thickness (close to the seasonal maximum, i.e. more than 60—70 cm). With small ice thicknesses, even strong ice pressure, as a rule, does not lead to a significant increase in the equivalent thickness of hummocks.

Deep Learning Low-cost Photogrammetry for 4D Short-term Glacier Dynamics Monitoring

AbstractShort-term monitoring of alpine glaciers is crucial to understand their response to climate change. This paper presents a low-cost multi-camera system tailored for 4D glacier monitoring using deep learning stereo-photogrammetry. Our approach integrates multi-temporal 3D reconstruction from stereo cameras and surface velocity estimation from a monoscopic camera through digital image correlation. To address the challenges posed by wide camera baselines in complex environments, we have integrated state-of-the-art deep learning feature matching algorithms into ICEpy4D, a Python toolkit designed for 4D monitoring (https://github.com/franioli/icepy4d). In a pilot study conducted on the debris-covered Belvedere Glacier (Italian Alps), our stereoscopic setup, with a camera base–height ratio close to one, captured daily images from May to November 2022. Our approach utilized SuperPoint and SuperGlue for feature matching, resulting in a daily 3D reconstruction of the glacier terminus, as traditional SIFT-like feature matching fails in this scenario. Using dense point clouds with decimetric accuracy, we estimated daily ice volume loss and glacier retreat at the terminus. The total ice volume loss was $$63\,000\,\text{m}$$ 63 000 m $${}^{3}$$ 3 and the retreat was $$17.8\,\text{m}$$ 17.8 m . Surface kinematics revealed three times higher surface velocity during the warm season (May–September) than in the fall (September–November). Daily analyses revealed a significant short-term correlation between air temperature, glacier surface velocity and ice ablation, providing insight into the glacier’s response to external forces. The low cost and ease of deployment of the proposed system facilitates replication at other sites for short-term monitoring of glacier dynamics.

Numerical simulations of recent and future evolution of Monte Perdido glacier

Glaciers are globally retreating due to climate change, and the Pyrenees Mountain range is no exception. This study uses the Open Global Glacier Model (OGGM) to explore the dynamics of the Monte Perdido glacier, one of the largest remaining glaciers in the Pyrenees. We explored three calibration approaches to assess their performances when reproducing observed volume decreases. The first approach involved mass balance calibration using terrestrial laser scanning data from 2011 to 2022 and climate data from a nearby weather station. The second approach used terrestrial laser scanning calibration with default climate data provided by OGGM (GSWP3-W5E5). The third approach used default geodetic mass balance calibration and default climate data. By comparing these calibration strategies and analysing historical data (terrestrial laser scanning and ground penetrating radar), we obtain insights of the applicability of OGGM to this small, mild conditions, Pyrenean glacier. The first calibration approach is identified as the most effective, emphasising the importance of selecting appropriate climate data and calibration methods. Additionally, we conducted future volume projections using an ensemble of General Circulation Models (GCMs) under the RCP2.6 and RCP8.5 scenarios. The results indicate a potential decrease in total ice volume ranging from 91.60% to 95.16% by 2100, depending on the scenario. Overall, this study contributes to the understanding of the Monte Perdido glacier’s behaviour and its response to climate change through the calibration of the OGGM, while also providing the first estimate of its future melting under different emission scenarios.

Late Neogene and Quaternary Lacustrine History of the Great Salt Lake-Bonneville Basin

The Great Salt Lake-Bonneville basin has contained lakes for many millions of years and has been hydrographically closed for most of its history. Lakes in the lacustrine system have ranged from saline to fresh, and from shallow to deep. Tectonics, specifically crustal extension, which began roughly 20 million years ago as part of the formation of the Basin and Range Province, is the cause of lake-basin formation. Much of the rock record of lakes from Miocene time is faulted and has been eroded and/or buried. Pliocene and Quaternary lakes are better known. For much of the past ~5 Ma the basin has probably appeared similar to today, with a shallow saline terminal lake in a dry desert surrounded by mountains. Freshwater marshes and fluvial systems existed on the basin floor during part of the past ~5 Ma, probably were caused by the lack of inflow from the upper Bear River during the Neogene Period and most of the Pleistocene Epoch (that river was diverted into the basin during the Late Pleistocene), combined with a warm and dry climate. The largest deep-lake cycles were caused by changes to a cold and wet climate, which affected the water budget of the lake system and were correlated with periods of global glaciation. Based on limited data, the total length of time deep lakes existed in the basin is thought to be less than 10% of the past ~773 ka. Lake Bonneville, the most-recent of the deep-lake cycles, was probably the deepest and largest manifestation of the lake system in the history of the basin. Named deep-lake cycles during the past ~773 ka, are Lava Creek (~620 ka), Pokes Point (~430 ka), Little Valley (~150 ka), Cutler Dam (~60 ka), and Bonneville (~30 -13 ka). Of the Quaternary deep-lake cycles, only Lake Bonneville is represented by lacustrine landforms, outcrops, and cores of offshore deposits; no landforms from older deep-lake cycles exist (some may be buried under Lake Bonneville deposits but are not visible at the surface), and pre-Bonneville lakes are represented by sediments in limited outcrops and drill holes (including a set of cores taken by A.J. Eardley in the mid 20th century). During the past ~773 ka, deep-lake cycles were correlated with changes in the total volume of global glacial ice; the available evidence indicates that prior to ~773 ka deep-lake cycles were rare.

Rapid mass losses of Urumqi River Basin glaciers, eastern Tianshan Mountains revealed from multi-temporal DEMs, 1964–2021

ABSTRACT Glacier volume changes have remarkable impacts on regional water resources; however, their estimation uncertainties remain large. In this study, the surface elevations of seven glaciers at the headwaters of the Urumqi River exhibited obvious thinning at the rate of 0.32 m a−1 from 1964 to 2021. Correlations between the ice volume change (dV) derived from surface elevation conversion and the area change (dS) were established for valley, cirque, and hanging glaciers. The ice volumes of valley, cirque, and hanging glaciers in the Urumqi River Basin decreased by 0.99 km3, 0.18 km3, and 0.59 km3, respectively, and the total ice volume decreased by 1.76 km3 during 1964–2021. Ice volume losses are accelerating. The correlation between dV and dS for valley glaciers produced a large estimation difference for the ice volume change of Urumqi Glacier No. 1 (UG1) compared with the glaciological mass balance (15%), while the estimation differences of ice volume changes for the three types of glaciers in the Urumqi River Basin were within acceptable limits (10%) based on the geodetic results. This new method has vast potential in estimating ice volume changes at the basin or regional scale, or even across western China.

Short- and Mid-Term Forecasting of Pan-Arctic Sea Ice Volume Using Variational Mode Decomposition and Bidirectional Long Short-Term Memory

The well-documented decrease in the annual minimum Arctic sea ice extent over the past few decades is an alarming indicator of current climate change. However, much less is known about the thickness of the Arctic sea ice. Developing accurate forecasting models is critical to better predict its changes and monitor the impacts of global warming on the total Arctic sea ice volume (SIV). Significant improvements in forecasting performance are possible with the advances in signal processing and deep learning. Accordingly, here, we set out to utilize the recent advances in machine learning to develop non-physics-based techniques for forecasting the sea ice volume with low computational costs. In particular, this paper aims to provide a step-wise decision process required to develop a more accurate forecasting model over short- and mid-term horizons. This work integrates variational mode decomposition (VMD) and bidirectional long short-term memory (BiLSTM) for multi-input multi-output pan-Arctic SIV forecasting. Different experiments are conducted to identify the impact of several aspects, including multivariate inputs, signal decomposition, and deep learning, on forecasting performance. The empirical results indicate that (i) the proposed hybrid model is consistently effective in time-series processing and forecasting, with average improvements of up to 60% compared with the case of no decomposition and over 40% compared with other deep learning models in both forecasting horizons and seasons; (ii) the optimization of the VMD level is essential for optimal performance; and (iii) the use of the proposed technique with a divide-and-conquer strategy demonstrates superior forecasting performance.

Reconstruction of palaeoglaciers and palaeoclimate in Zheduo Shan, Eastern Tibetan Plateau, during the Last Glacial Maximum

Reconstructing the extent and timing of palaeoglaciers and their associated climate is of great importance for understanding the responses of glaciers to climate change. Glacial landforms are well-preserved in Zheduo Shan, one of the high mountain ranges on the eastern Tibetan Plateau (TP). However, few studies have constrained glacial chronologies and estimated palaeoclimate in this area. We investigated the glacial advance during the Last Glacial Maximum (LGM) in Zheduo Shan using 10Be surface exposure dating. We then reconstructed the extent and thickness of LGM glaciers based on geomorphological mapping and a flowline-based glacial model-PalaeoIce. Eleven 10Be exposure ages confirmed a major LGM glacial advance between 20.0 ± 3.2 ka and 19.3 ± 2.8 ka. The reconstructed LGM glaciers in this mountain range covered an area of 499.16 km2 with an average ice thickness of 54.4 m and a total ice volume of 52.82 km3. The regional average equilibrium-line altitude (ELA) was estimated as 4524 ± 140 m, 535 ± 140 m lower than the present value. Based on the empirical relationship between precipitation and temperature (P-T model) at the ELAs on the TP, the temperature and precipitation were estimated as 3.10–5.27 °C and 10–16% lower during the LGM than the present values, respectively. These results suggest that the LGM glacial advance was more sensitive to temperature than precipitation in Zheduo Shan.

Glacier slowdown and rapid ice loss in the Tinguiririca and Cachapoal Basin, Central Andes of Chile

The central region of Chile is home to nearly 10 million people, 60% of the country's population. This area's water supply is reliant on glacial meltwater from the Andes, especially during the dry summer months. However, the current ice volumes and rates of ice loss remain uncertain in many glacierized Andean basins. Our study investigated the dynamics of glaciers located in the high-altitude Tinguiririca and Cachapoal Basin over the period 2016–2022, by measuring their surface velocity and inverting for changes in ice thickness. We measured the glacier surface velocities using the Glacier Image Velocimetry toolbox on Sentinel 2 images, merging over 6000 individual velocity measurements into median annual velocity maps. We then used ice velocities as input for ice-thickness inversions to calculate ice-thickness maps and ice volumes using an ensemble of four different methods. We detect a decrease in surface velocity from 2016 to 2022 on the Universidad, Cortaderal, Norte Cipreses glaciers and southern part of the Palomo glacier, while the Cipreses glacier and the northern part of the Palomo glacier showed a decrease in velocity between 2016 and 2021 and then an acceleration in 2022. Ice thickness data shows an ice volume loss of between 0.34 ± 0.22 and 0.43 ± 0.18 km3/yr depending on the method used, equivalent to ∼25% of the total ice volume lost from 2016 to 2022. The current rates of ice volume loss are unsustainable beyond the next two decades, reducing or entirely removing the glacial contribution to streamflow and increasing pressure on local water resources.

Southern limit of the Patagonian Ice Sheet

The southern limit of the Patagonian Ice Sheet at glacial maxima is poorly constrained due to a paucity of field data. This particularly applies to southern outlet glaciers of the Cordillera Darwin whose full extents have been debated by glacial geologists since 1899 CE, introducing uncertainty into estimates of total ice volume. Here we report on the stratigraphy of exposed stratigraphic sections on the west coast of Isla Hermite which include glacial diamict with discontinuous boulder pavement, overlain by successions of peats and sandy silt. The location of these sections, orientation of clasts within the glacial diamict, and geomorphology of the adjacent marine trough, suggest that an ice stream extended south from an ice centre at Cordillera Darwin across an extended Magellan outwash plain, through Paso Mantellero, to Islas Hermite and Cabo de Hornos (Cape Horn). This was similar in extent to the Canal Beagle and Lago Fagnano Ice Lobes which extended to the east. Retreat occurred sometime before 12,880 cal yr BP based on radiocarbon dated peat macrofossils immediately overlying the glacial diamict. We discuss whether this is a close minimum age, or a product of delayed onset of peat accumulation at the sampling site.

Three-dimensional imaging of martian glaciated terrain using Mars Reconnaissance Orbiter Shallow Radar (SHARAD) observations

We present a three-dimensional radargram of a 13° x 11° region of Deuteronilus Mensae, produced from 457 Mars Reconnaissance Orbiter Shallow Radar (SHARAD) observations. We assess the viability of the 3D imaging algorithms developed to work with SHARAD observations in mid-latitude regions of interest. The quality of subsurface imaging in topographically complex regions is highly improved due to the proper positioning and mitigation of off-nadir reflections in the resulting image. The initial analysis of debris-covered glaciers using 3D radargrams has yielded results that are consistent with previous 2D-based mapping efforts. However, the use of 3D radargrams has enabled the analysis of 3× more area resulting in more accurate estimates of total ice volume, indicating over 9% more ice than previously estimated. Such discrepancies have important implications for Mars climate history studies and in situ resource utilization. The success of this imaging study paves the way for future 3D radargrams in the martian mid-latitudes and stands to increase our confidence in the distribution of many subsurface features of interest.

Brief communication: Rapid ∼ 335 × 106 m3 bed erosion after detachment of the Sedongpu Glacier (Tibet)

Abstract. Following the 130 ± 5 × 106 m3 detachment of the Sedongpu Glacier, south-eastern Tibet, in October 2018, the Sedongpu Valley, which drains into the Yarlung Tsangpo (Brahmaputra) River, underwent rapid large-volume landscape changes. Between December 2018 and 2022 and in particular during summer 2021, an enormous volume of in total ∼ 335 ± 5 × 106 m3 was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width, and almost 4 km length. The 2021 erosion peak happened through massive but still gradual retrogressive erosion into the former glacier bed. Several rock–ice avalanches of in total ∼ 150 ± 5 × 106 m3 added to the total rock, sediment, and ice volume of over 600 × 106 m3 (0.6 km3) that has been exported from the basin since around 2017. The recent erosion volumes at Sedongpu are by order of magnitude equivalent to the average annual denudation volume of the entire Brahmaputra basin upstream of the location where the river leaves the Himalayas. This high-magnitude low-frequency event illustrates the potential for rapid post-glacial landscape evolution and associated hazards that has rarely been observed and considered at such high intensity so far.

Microplastics Records from the Southern Ocean Sediments

ABSTRACT The study records the extent of microplastics distribution in the surficial sediments of the Southern Ocean. This represents the first study of microplastics in the sediments of Prydz Bay, Southern Ocean. Prydz Bay is the largest embayment located in the Indian Ocean Sector of the Southern Ocean and receives sediments supplied by the Lambert Glacier/Amery Ice Shelf, draining approximately 10% of the total ice volume of Antarctica. It is an important site of circumpolar deep water (CDW) and Antarctic bottom water (AABW) formation. This study focuses on the distribution of microplastics in the sediments of the Prydz Bay, Southern Ocean with special reference to the ecological risk factor of these microplastics. The type distribution of microplastics revealed percent content as bead > fiber > fragment. Ecological risk factors (CF and PLI) of microplastics in sediment samples revealed a minor to major risk of these pollutants in the analyzed environment. Statistical analyses such as principal component analysis (PCA), ANOVA, Tukey's HSD test, and correlation analysis were performed to highlight the interrelationship of MPN with CF, PLI, pH, TOC, and sediment texture. The levels of microplastic pollution in the Prydz Bay are significant on a local scale, particularly around research stations. This report underlines the immediacy of microplastic pollution management in the Southern Ocean to maintain the serenity of this pristine marine habitat. So further research on the information of microplastics policy discussions to develop appropriate management responses.

Effects of cryogenic condition and chemistry on the properties of synthetic and biopolymer cryogels

We discuss here the properties of seven different synthetic and biopolymer cryogels prepared under identical conditions, and how the cryogenic condition and chemistry affect their properties. The monomers used in the study are acrylamide (AAm), N, N-dimethylacrylamide (DMAA), sodium acrylate (NaAA), sodium methacrylate (NaMA), and 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS). Silk fibroin (SF), and double-stranded deoxyribonucleic acid (DNA) are selected as the biopolymers for the preparation of the cryogels. The nonionic monomers AAm and DMAA produce cryogels with the largest total pore volumes and average pore diameters while ionic cryogels exhibit a small pore volume due to the collapse of the pores during their drying. Moreover, SF cryogel has the most mechanically stable porous structure followed by AAm and DMAA cryogels. The experimental findings can be explained with the cryogenic conditions namely, the total ice volume in the cryogelation system and the true concentration of the monomers or polymers in the unfrozen domains after cryoconcentration, as determined from DSC measurements. The extent of cryoconcentration and hence the true concentration of the monomers or polymers regulate the mechanical stability of the cryogel pore walls.

Comparative Analysis of Sea Ice Between the Antarctic and the Arctic

Polar regions have a profound impact on global climate change, because polar regions are one of the world’s largest sources of cold. Sea ice is the main influencing factor in the polar regions, which has a great influence on the heat transfer, which in turn affects the global climate system. In the past two decades, Arctic sea ice has decreased year by year, while Antarctic sea ice has increased. The use of passive satellite remote sensing data for long-term observation and analysis of polar sea ice will provide an important theoretical basis for studying global climate change and an important data source for polar sea ice research. This study uses the data of the Antarctic and Arctic sea ice density data from 1998 to 2018 to compare and analyze the changes in time and space to find out the changes of the sea ice in the south and Arctic. Using the SSM / I data of the US National Defense Meteorological Satellite and the NASA TEAM algorithm, the sea ice data from 1998 to 2018 was compared and analyzed. The specific process is to use the NASA TEAM algorithm to invert the Arctic and Arctic sea ice, obtain multi-year ice, one-year ice, and overall sea ice density data, and then determine the sea ice area. Through comparative analysis, it is found that the area of Antarctic sea ice is significantly larger than that of the North Pole, and the change trend of the two is similar. The downward trend is greater than that of the South Pole; the total annual ice volume of the South Pole is greater than that of the North Pole, both of which have an upward trend, and the Arctic has a greater increase; the overall sea ice has fallen, and the multi-year ice has decreased while the annual ice has increased. Sea ice has a tendency to transform from multi-year ice to one-year ice; Antarctic multi-year ice is mainly distributed in the Weddell Sea, with stable areas accounting for 60% of the multi-year ice area; Antarctica is dominated by one-year ice, and one-year ice stable area accounts for one 80.1% of the total annual ice area; Arctic multi-year ice mainly exists in the central area of the Arctic Ocean. The Arctic multi-year ice stable area only accounts for 35.06%; the Arctic one-year ice is mainly distributed around the multi-year ice periphery, and the stable existence area accounts for the total annual ice area 48.5%.

Mapping of Glaciers on Horseshoe Island, Antarctic Peninsula, with Deep Learning Based on High-Resolution Orthophoto

Antarctica plays a key role in the hydrological cycle of the Earth’s climate system, with an ice sheet that is the largest block of ice that reserves Earth’s 90% of total ice volume and 70% of fresh water. Furthermore, the sustainability of the region is an important concern due to the challenges posed by melting glaciers that preserve the Earth’s heat balance by interacting with the Southern Ocean. Therefore, the monitoring of glaciers based on advanced deep learning approaches offers vital outcomes that are of great importance in revealing the effects of global warming. In this study, recent deep learning approaches were investigated in terms of their accuracy for the segmentation of glacier landforms in the Antarctic Peninsula. For this purpose, high-resolution orthophotos were generated based on UAV photogrammetry within the Sixth Turkish Antarctic Expedition in 2022. Segformer, DeepLabv3+ and K-Net deep learning methods were comparatively analyzed in terms of their accuracy. The results showed that K-Net provided efficient results with 99.62% accuracy, 99.58% intersection over union, 99.82% precision, 99.76% recall and 99.79% F1-score. Visual inspections also revealed that K-Net was able to preserve the fine details around the edges of the glaciers. Our proposed deep-learning-based method provides an accurate and sustainable solution for automatic glacier segmentation and monitoring.

Towards accurate quantification of ice content in permafrost of the Central Andes – Part 2: An upscaling strategy of geophysical measurements to the catchment scale at two study sites

Abstract. With ongoing climate change, there is a pressing need to better understand how much water is stored as ground ice in areas with extensive permafrost occurrence, as well as how the regional water balance may alter in response to the potential generation of meltwater from permafrost degradation. However, field-based data on permafrost in remote and mountainous areas such as the South American Andes are scarce. Most current ground ice estimates are based on broadly generalized assumptions such as volume–area scaling and mean ground ice content estimates of rock glaciers. In addition, ground ice contents in permafrost areas outside of rock glaciers are usually not considered, resulting in a significant uncertainty regarding the volume of ground ice in the Andes and its hydrological role. In Part 1 of this contribution, Hilbich et al. (2022a) present an extensive geophysical data set based on electrical resistivity tomography and refraction seismic tomography surveys to detect and quantify ground ice of different landforms and surface types in several study regions in the semi-arid Andes of Chile and Argentina with the aim to contribute to the reduction of this data scarcity. In Part 2 we focus on the development of a strategy for the upscaling of geophysics-based ground ice quantification to an entire catchment to estimate the total ground ice volume (and its approximate water equivalent) in the study areas. In addition to the geophysical data, the upscaling approach is based on a permafrost distribution model and classifications of surface and landform types. In this paper, we introduce our upscaling strategy, and we demonstrate that the estimation of large-scale ground ice volumes can be improved by including (i) non-rock-glacier permafrost occurrences and (ii) field evidence through a large number of geophysical surveys and ground truthing information. The results of our study indicate that (i) conventional ground ice estimates for rock-glacier-dominated catchments without in situ data may significantly overestimate ground ice contents and (ii) substantial volumes of ground ice may also be present in catchments where rock glaciers are lacking.

Modeling the climate sensitivity of Patagonian glaciers and their responses to climatic change during the global last glacial maximum

Investigation of the behavior of the former ice sheet over Patagonia aids better understanding of ice-climate interactions and has important implications for deciphering how modern glaciers will respond to rapid increase in global temperature. Here, we use a 1-km resolution ice sheet model to identify the climate sensitivity of Patagonian glaciers and examine their responses to climatic change during the global Last Glacial Maximum (gLGM). Our results demonstrate that the total glacier area increases by ∼78 × 103 km2 and the equilibrium-line altitude (ELA) lowers by ∼163 m for every 1 °C of cooling under modern precipitation regime. Keeping temperature unchanged, there is an increase of total glacier area by ∼21 × 103 km2 and a ΔELA by ∼64 m for every doubling in precipitation. According to the multimodel ensemble mean of 21 PMIP models, an overall colder and drier climate prevails over Patagonia during the gLGM, with a decrease of annual mean temperature and precipitation by ∼4.7 °C and 12%, respectively. Under the modeled gLGM climate, there is an extensive ice sheet (∼387 × 103 km2) almost completely covering the Patagonian Andes, which results largely from the cooling with positive contribution from sea-level fall. The Patagonian ice sheet is drained by ice streams at the western margins and fast-flowing outlet glaciers to the east, with a north-to-south ice divide mainly extending the southern Patagonian Andes. Additionally, the erosion potential induced by the ice sheet exhibits a very strong localization over the fjords and valleys, resembling the pattern of ice velocity. The modeled ice sheet extent and ice flow pattern during the gLGM match well with the latest empirical reconstructions (though with spatial discrepancies), whereas the total ice volume is underestimated. However, the modeled Patagonian ice sheet exhibits high sensitivity to climatic forcing and the values of ice sheet model parameters used.

Effects of ocean mesoscale eddies on atmosphere–sea ice–ocean interactions off Adélie Land, East Antarctica

Heat and momentum exchanges at the Southern Ocean surface are crucial for the Earth’s Climate, but the importance of the small-scale spatial variability of these surface fluxes is poorly understood. Here, we explore how small-scale heterogeneities of the surface conditions due in particular to ocean eddies affect the atmosphere–sea ice–ocean interactions off Adélie Land, in East Antarctica. To this end, we use a high-resolution regional atmosphere–sea ice–ocean coupled model based on the NEMO-LIM and MAR models. We explore how the atmosphere responds to small-scale heterogeneity of the ocean or sea ice surface conditions, how eddies affect the sea ice and atmosphere, and how the eddy-driven surface fluxes impact the heat, freshwater, and momentum budget of the ocean. The atmosphere is found to be more sensitive to small-scale surface temperature gradients above the ice-covered than above the ice-free ocean. Sea ice concentration is found to be weaker above anticyclonic than cyclonic eddies due to increased sea ice melting or freezing (0.8 cm/day) partly compensated by sea ice convergence or divergence. The imprint of ice-free eddies on the atmosphere is weak, but in the presence of sea ice, air warming (+ 0.3 ^{circ }C) and wind intensification (+ 0.1 m/s) are found above anticyclonic eddies, while cyclonic eddies have the opposite effects. Removing the interactions of eddies with the sea ice or atmosphere does not affect the total sea ice volume, but increases the ocean kinetic energy by 8% and weakens northward advection of sea ice, leading to a 15% decrease in freshwater flux north of 62.5 ^{circ }S and weaker ocean restratification.