Instituto Nacional de Ciência e Tecnologia da Criosfera

Abstract. We describe the seasonal and interannual variability of volume transports in the Weddell and Ross Seas using the 1/12° 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5 ± 2.9 Sv (1 Sv ≡ 106 m3 s−1) and 13.4 ± 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW) (defined by neutral density γn ≥ 28.27 kg m−3) from the Weddell and Ross Seas of 10.6 ± 3.1 Sv and 0.5 ± 0.7 Sv, respectively, agree with the range reported in historical observational studies. The export of Weddell Sea dense water in OCCAM is primarily determined by the strength of the Weddell Gyre. Variability in AABW export is predominantly at periods of ~1 yr and 2–4 yr.

Glaciers are natural sensors to identify changes in climate and weather patterns, so the importance of monitoring them in a forceful way. In this paper, we show the development and application of a set of low cost sensors, customized for the characteristics of glacial environments. Two modules are part of the project: (1) an Automatic Weather Station; and (2) an Electronic Ablation Station. We also show the results of field tests performed on glaciers of southern Patagonia. Keywords: AWS, Glaciology, Climatology, Arduino, Ice Melting

Among the regions of the Southern Ocean, the northern Antarctic Peninsula (NAP) has emerged as a hotspot of climate change investigation. Nonetheless, studies have indicated issues and knowledge gaps that must be addressed to expand the understanding of the carbonate system in the region. Therefore, we focused on identifying current knowledge about sea-air CO2 fluxes (FCO2), anthropogenic carbon (Cant) and ocean acidification along NAP and provide a better comprehension of the key physical processes controlling the carbonate system. Regarding physical dynamics, we discuss the role of water masses formation, climate modes, upwelling and intrusions of Circumpolar Deep Water, and mesoscale processes. For FCO2, we show that the summer season corresponds to a strong sink in coastal areas, leading to CO2 uptake that is greater than or equal to that of the open ocean. We highlight that the prevalence of summer studies prevents comprehending processes occurring throughout the year and the net annual CO2 balance in the region. Thus, temporal investigations are necessary to determine natural environmental fluctuations and to distinguish natural variability from anthropogenically driven changes. We emphasize the importance of more studies regarding Cant uptake rate, accumulation, and export to global oceans.

ABSTRACT This paper reports a comparative analysis performed on a fraction-image time series of the Antarctic Peninsula from the period 1999–2009 generated by multiresolution remote-sensing images (SSM/I and SSMI/S with 25 km and QuikSCAT with 2.225 km spatial resolutions) for snow-melt detection. Our method is based on the (a) preprocessing of multitemporal remote-sensing data, (b) subpixel mixture analysis of SSMI and QuikSCAT image time series, and (c) evaluation of subpixel analysis, including an assessment of fraction images of wet snow using an independent ASAR dataset and sensitivity analysis on the melt metrics measured by these images. The temporal dynamics of the melt indices derived from the wet-snow fraction images presented a more realistic pattern than the traditional melt metrics measured by Boolean snow-melt detection approaches. Because the snow melt actually occurs at the pixel fractions, the multiscale analysis that was performed suggests an overestimation of the melt metrics calculated using Boolean approaches (which assume that the entire area of the detected pixel shows snow melt). The melt metrics measurements show an overestimation according to the decrease in spatial resolution related to the multiplicative effect of a larger pixel area.

Global warming and its consequences on polar regions have been thoroughly discussed in recent times. One of those consequences is the freshwater flux and the associated cooling and freshening that result from iceberg melting. Despite the potential impact, large uncertainties exist resulting mostly from the complexity to follow icebergs from space, which make the few existing estimates essentially model-based. This study takes advantage of state-of-art machine learning methods to present novel prevalent trajectories and potential freshwater input from 450 icebergs ranging from 1 to 2765 km2 across the northwestern Weddell Sea, Antarctica. The main results highlight the predominance of a northward flux and the entrance of icebergs up to 10 km2 into Bransfield Strait associated with the main current systems along the Antarctic Peninsula. The present analysis on such a large number of icebergs unveils an average drift speed of 3.4 ± 2.7 km day-1 and an average disintegration rate of ~62% per year, representing an integrated potential regional freshwater input of 133.62 Gt yr-1. Altogether, this study adds new knowledge to the complex problem of autonomous applications for iceberg detection and tracking, further exploring such methods on a very dynamic region of singular importance for the ocean and climate studies.

Similar to the Patagonian Icefields, the Cordillera Darwin Icefield in Tierra del Fuego experienced important ice loss during the last decades. The difficult accessibility and the harsh weather conditions in that area result in scarce in-situ observations of climatic conditions and glacier mass balances. Under these challenging conditions, this study investigates calibration strategies of surface mass balance models in the Monte Sarmiento Massif, western Cordillera Darwin, with the goal to achieve realistic simulations of the regional surface mass balance in the period 2000-2022.We apply three calibration strategies ranging from a local single-glacier calibration to a regional calibration with and without the inclusion of a snowdrift parametrization. Furthermore, we apply four models of different complexity ranging from an empirical degree-day model to a fully-fledged surface energy balance model. This way, we examine the model transferability in space, the benefit of including regional mass change observations as calibration constraint and the advantage of increasing the model complexity regarding included processes. In-situ measurements comprise ablation stakes, ice thickness surveys and weather station records at Schiaparelli Glacier as well as elevation changes and flow velocity from satellite data for the entire study site. Performance of simulated surface mass balance is validated against geodetic mass changes and stake observations of surface melting.Results show that transferring mass balance models in space is a challenge, and common practices can produce distinctly biased estimates. The use of remotely sensed regional observations can significantly improve model performance. Increasing the complexity level of the model does not result in a clear improvement in our case where all four models perform similarly. Including the process of snowdrift, however, significantly increases the agreement with geodetic mass balances. This highlights the important role of snowdrift for the surface mass balance in the Cordillera Darwin, where strong and consistent westerly winds prevail.

Abstract This paper provides the first evidence for sea-ice formation in the Cordillera Darwin (CD) fjords in southern Chile, which is farther north than sea ice has previously been reported for the Southern Hemisphere. Initially observed from a passenger plane in September 2015, the presence of sea ice was then confirmed by aerial reconnaissance and subsequently identified in satellite imagery. A time series of Sentinel-1 and Landsat-8 images during austral winter 2015 was used to examine the chronology of sea-ice formation in the Cuevas fjord. A longer time series of imagery across the CD was analyzed from 2000 to 2017 and revealed that sea ice had formed in each of the 13 fjords during at least one winter and was present in some fjords during a majority of the years. Sea ice is more common in the northern end of the CD, compared to the south where sea ice is not typically present. Is suggested that surface freshening from melting glaciers and high precipitation reduces surface salinity and promotes sea-ice formation within the semi-enclosed fjord system during prolonged periods of cold air temperatures. This is a unique set of initial observations that identify questions for future research in this remote area.

For an analysis of the region of Manaus (AM), they were of great importance the collection and analysis of GPR data. GPR, has become increasingly popular in the acquisition of geophysical data because it is a device that presents greater ease in its operation. But although it does not require a deep understanding of physical concepts, it is of great importance for the operator to know the fundamental concepts of the method and also understand about data collection and processing. The processing of the data collected by GPR consisted in the treatment and filtering of images applying filters and gains, thus facilitating their identification and interpretation. This processing allowed the visualization of supposed faults in places that have a high factor of weathering and of difficult surface observation.

We show high-quality images of a constructed multi-channel radar dataset along a shore–normal profile on Marambaia Barrier Island. The multi-channel dataset was constructed by assembling traces from seven collinear fixed offset profiles obtained with a 100 MHz bistatic equipment. The traces are binned and stacked as sparse 7-trace common-source gathers along the entire profile. We deal with the alias of each common-source gather through trace interpolation, yielding adequately sampled, unaliased, dense gathers. With the interpolated gathers we have produced a stack section and estimated a 2-D velocity model spanning over the whole profile. We have also produced pre-stack time and depth migrated sections of the subsurface. All sections obtained from the common-source gathers have a degree of quality far beyond what would be possible to obtain with a usual fixed-offset survey, eventually complemented with a limited number of multi offset gathers for the estimation of 1-D velocity models. In addition, the 1-D velocity model derived from a CMP gather is even unable to estimate the velocity distribution at its central point. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 207A (Anaheim Convention Center) Presentation Type: Oral

This work uses a GPR dataset acquired at West Antarctica to demonstrate a viable methodology in estimating the depth to bedrock by the observed increasing dip with depth seen in the reflectors, which we have heuristically hypothesized to be linked to a quasi-static flow of ice downhill to the SW, and then curving toward the NW, following the general trend of the ice sheet to the ocean. We have resorted to the first-order shear deformation plate theory in order to numerically model the static, flexural response of a homogeneous, isotropic, elastic, ice plate due to the loading of its overburden combined to its own weight.

In this work, several fixed-offset GPR data was acquired in Marambaia barrier island. These data are processed to simulate multi-channels acquisition and thus allow the estimation of the 2-D velocity model in time of the subsurface area data. The imaging data obtained from these reflectors focused best shown with greater number of refractions being collapsed, when compared with the imaging obtained in conventional manner GPR data, which is used 1-D velocity model.

Abstract. We describe the seasonal and interannual variability of volume transports in Weddell and Ross Seas using the 1/12° 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5 ± 2.9 Sv (1 Sv ≡ 106 m3 s−1) and 13.4 ± 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW) (defined by neutral density γn ≥ 28.27 kg m−3) from the Weddell and Ross Seas of 10.6 ± 3.1 Sv and 0.5 ± 0.7 Sv, respectively, agree with the range reported in historical observational studies. Variability in AABW export is predominantly at periods of ~1 yr and 2–4 yr. The transit time taken by AABW sourced in the Southern Weddell Sea to reach the main Weddell export zone is ~2 yr. Lagged correlation between the thermohaline properties of AABW source waters and AABW export indicates that recent shelf waters freshening trends are likely related to changes in the AABW outflow rates.

Abstract. This study investigates strategies for melt model calibration in the Monte Sarmiento Massif (MSM), Tierra del Fuego, with the goal to achieve realistic simulations of the regional surface mass balance (SMB). Applied calibration strategies range from a local single-glacier calibration to a regional calibration with the inclusion of a snowdrift parametrization. We apply four SMB models of different complexity. This way, we examine the model transferability in space, the benefit of regional mass change observations and the advantage of increasing the complexity level regarding included processes. Measurements include ablation and ice thickness observations at Schiaparelli Glacier as well as elevation changes and flow velocity from satellite data for the entire study site. Performance of simulated SMB is validated against geodetic mass changes and stake observations of surface melting. Results show that transferring SMB models in space is a challenge, and common practices can produce distinctly biased estimates. Model performance can be significantly improved by the use of remotely sensed regional observations. Furthermore, we have shown that snowdrift does play an important role for the SMB in the Cordillera Darwin, where strong and consistent winds prevail. The massif-wide average annual SMB between 2000 and 2022 falls between -0.25 and -0.07 m w.e. yr-1, depending on the applied model. SMB is mainly controlled by surface melting and snowfall. The model intercomparison does not indicate one obviously best-suited model for SMB simulations in the MSM.

O propósito deste artigo é discutir a evolução dos métodos de simulação do retroespalhamento radar/SAR em massas de neve e gelo, compreendendo as abordagens físicas e empíricas neste processo. O presente trabalho busca compilar os diversos modelos de retroespalhamento radar/SAR de neve e gelo na faixa de microondas compreendida pela banda X propostos na literatura, comparando seus resultados, contribuições e limitações a fim de promover um material de orientação para pesquisa e emprego dos diversos modelos de retroespalhamento atualmente disponíveis. Assim, os principais modelos de retroespalhamento atuais serão descritos, implementados e finalmente comparados. Como fonte de validação dos modelos, serão considerados dados comuns de entrada, constituídos de dados estratigráficos e de temperatura da neve em um perfil de 2m de profundidade e dados radar/SAR Cosmo-SkyMed na banda X coletados na região da geleira Union no verão antártico de 2011-2012.