nasa-gesdisc/es-publications-researchareas huggingface dataset:
Sediment-laden sea ice in southern Hudson Bay: Entrainment, transport, and biogeochemical implications (2021)

During a research expedition in Hudson Bay in June 2018, vast areas of thick (>10 m), deformed sediment-laden sea ice were encountered unexpectedly in southern Hudson Bay and presented difficult navigation conditions for the Canadian Coast Guard Ship Amundsen. An aerial survey of one of these floes revealed a maximum ridge height of 4.6 m and an average freeboard of 2.2 m, which corresponds to an estimated total thickness of 18 m, far greater than expected within a seasonal ice cover. Samples of the upper portion of the ice floe revealed that it was isothermal and fresh in areas with sediment present on the surface. Fine-grained sediment and larger rocks were visible on the ice surface, while a pronounced sediment band was observed in an ice core. Initial speculation was that this ice had formed in the highly dynamic Nelson River estuary from freshwater, but 18O isotopic analysis revealed a marine origin. In southern Hudson Bay, significant tidal forcing promotes both sediment resuspension and new ice formation within a flaw lead, which we speculate promotes the formation of this sediment-laden sea ice. Historic satellite imagery shows that sediment-laden sea ice is typical of southern Hudson Bay, varying in areal extent from 47 to 118 km2 during June. Based on an average sediment particle concentration of 0.1 mg mL1 in sea ice, an areal extent of 51,924 km2 in June 2018, and an estimated regional end-of-winter ice thickness of 1.5 m, we conservatively estimated that a total sediment load of 7.8  106 t, or 150 t km2, was entrained within sea ice in southern Hudson Bay during winter 2018. As sediments can alter carbon concentrations and light transmission within sea ice, these first observations of this ice type in Hudson Bay imply biogeochemical impacts for the marine system.

Research areas: Cryospheric Indicators
Increasing dust emission from ice free terrain in southeastern Greenland since 2000 (2021)

Mineral dust plays a key role in both local and global climates. At high latitudes, atmospheric dust can affect ice-nuclei formation, and surface dust can reduce the albedo as well as increase subsequent ice melting. As a proxy for past climate, mineral dust is preserved in ice cores, but few studies have examined deposited dust in ice cores during the Anthropocene, especially after 2000. We measured dust concentrations in an ice core at the southeastern dome in Greenland (SE-Dome), and reconstructed the annual and seasonal dust fluxes during 19602014. We find the annual average flux during 19602014 to be 34.8  13.5 mg m2 yr1, a value about twice that of ice cores further inland. The more recent part of that period, 20002014, has the higher annual flux of 46.6  16.2 mg m2 yr1. The annual and autumn dust fluxes highly correlate with air temperature in Tasiilaq (r = 0.61 and 0.50, respectively), a coastal location in southeastern Greenland. Our results suggest that the local dust emissions at the coastal region are increasing due to a decreasing seasonal snow-cover area arising from coastal Greenland warming after 2000.

Research areas: Cryospheric Indicators
Spatio-temporal Analyses of Sea Ice Conditions over Two Seas of Arctic Ocean (2023)

Sea ice conditions over the Arctic can be studied remotely using various satellites. In the current paper, two seas of the Arctic, Beaufort and Laptev are considered. The difference in the sea ice conditions of Beaufort and Laptev is separately observed using the parameters; Sea Ice Area, Concentration and Thickness for the span of 20102021. In order to understand the peripheral and lateral condition of sea ice in a given region for a given time, we have attempted to understand each derivable product of the sea ice spatially and temporally throughout its life cycle. It has been found that the Laptev which is a major warehouse of arctic sea ice with an average outflow of 483,000 km2 per year is found to have a low range of Sea Ice Area and Thickness. Laptev Sea Ice Thickness maxima shift from 1 to 1.21.3 to 1.4 m from January to February to March. Whereas over Beaufort, the peak of Sea Ice Thickness shifts from 1.2 to 1.5 to 1.7 m from January to February to March. This means the variability in Beaufort is higher than that in Laptev. The method discussed in this paper presents a unique idea of using the Sea Ice Thickness variable over Sea Ice Area and Concentration, especially during winter months, for a better understanding of the sea ice growth. The information obtained using these sea ice parameters would be further utilized by modelers, navigators, etc., which in turn helps improve, forecast studies.

Research areas: Cryospheric Indicators
Has Arctic sea ice loss contributed to increased surface melting of the Greenland ice sheet? (2016)

Abstract In recent decades, the Greenland ice sheet has experienced increased surface melt. However, the underlying cause of this increased surface melting and how it relates to cryospheric changes across the Arctic remain unclear. Here it is shown that an important contributing factor is the decreasing Arctic sea ice. Reduced summer sea ice favors stronger and more frequent occurrences of blocking-high pressure events over Greenland. Blocking highs enhance the transport of warm, moist air over Greenland, which increases downwelling infrared radiation, contributes to increased extreme heat events, and accounts for the majority of the observed warming trends. These findings are supported by analyses of observations and reanalysis data, as well as by independent atmospheric model simulations using a state-of-the-art atmospheric model that is forced by varying only the sea ice conditions. Reduced sea ice conditions in the model favor more extensive Greenland surface melting. The authors find a positive feedback between the variability in the extent of summer Arctic sea ice and melt area of the summer Greenland ice sheet, which affects the Greenland ice sheet mass balance. This linkage may improve the projections of changes in the global sea level and thermohaline circulation.

Research areas: Cryospheric Indicators
Mass evolution of the Antarctic Peninsula over the last 2 decades from a joint Bayesian inversion (2022)

Abstract. The Antarctic Peninsula has become an increasingly important component of the Antarctic Ice Sheet mass budget over the last 2 decades, with mass losses generally increasing. However, due to the challenges presented by the topography and geometry of the region, there remain large variations in mass balance estimates from conventional approaches and in assessing the relative contribution of individual ice sheet processes. Here, we use a regionally optimized Bayesian hierarchical model joint inversion approach that combines data from multiple altimetry studies (ENVISAT, ICESat, CryoSat-2 swath), gravimetry (GRACE and GRACE-FO), and localized DEM differencing observations to solve for annual mass trends and their attribution to individual driving processes for the period 20032019. This is first time that such localized observations have been assimilated directly to estimate mass balance as part of a wider-scale regional assessment. The region experienced a mass imbalance rate of -191.1 Gt yr1 between 2003 and 2019, predominantly driven by accelerations in ice dynamic mass losses in the first decade and sustained thereafter. Inter-annual variability is driven by surface processes, particularly in 2016 due to increased precipitation driven by an extreme El Nino, which temporarily returned the sector back to a state of positive mass balance. In the West Palmer Land and the English Coast regions, surface processes are a greater contributor to mass loss than ice dynamics in the early part of the 2010s. Our results show good agreement with conventional and other combination approaches, improving confidence in the robustness of mass trend estimates, and in turn, understanding of the region's response to changes in external forcing.

Research areas: Cryospheric Indicators, Atmospheric/Ocean Indicators
A Full-Stokes 3-D Calving Model Applied to a Large Greenlandic Glacier (2018)

Iceberg calving accounts for around half of all mass loss from both the Greenland and Antarctic ice sheets. The diverse nature of calving and its complex links to both internal dynamics and climate make it challenging to incorporate into models of glaciers and ice sheets. Here we present results from a new open-source 3-D full-Stokes calving model developed in Elmer/Ice. The calving model implements the crevasse depth criterion, which states that calving occurs when surface and basal crevasses penetrate the full thickness of the glacier. The model also implements a new 3-D rediscretization approach and a time-evolution scheme which allow the calving front to evolve realistically through time. We test the model in an application to Store Glacier, one of the largest outlet glaciers in West Greenland, and find that it realistically simulates the seasonal advance and retreat when two principal environmental forcings are applied. These forcings are (1) submarine melting in distributed and concentrated forms and (2) ice mélange buttressing. We find that ice mélange buttressing is primarily responsible for Store Glacier's seasonal advance and retreat. Distributed submarine melting prevents the glacier from forming a permanent floating tongue, while concentrated plume melting has a disproportionately large and potentially destabilizing effect on the calving front position. Our results also highlight the importance of basal topography, which exerts a strong control on calving, explaining why Store Glacier has remained stable during a period when neighboring glaciers have undergone prolonged interannual retreat.

Research areas: Cryospheric Indicators
Backward and forward drift trajectories of sea ice in the northwestern (2019)

To track sea ice motion, four ice‑tethered buoys were deployed at 84.6°N and 144.3°W, 87.3°N and 172.3°W, 81.1°N and 157.4°W, and 82.8°N and 166.5°W in summers of 2008, 2010, 2014, and 2016, respectively. In addition, the remote sensed ice motion product provided by National Snow and Ice Data Center was used to reconstruct backward and forward ice drifting trajectories from the buoy deployment sites during 1979–2016. Sea ice in the central Arctic Ocean in late summer is trending to have travelled from lower latitudes, and to be advected to the region more involved in the Transpolar Drift Stream (TDS) during 1979–2016. The strengthened TDS has played a crucial role in Arctic sea ice loss from a dynamic perspective. The trajectory of ice is found to be significantly related to atmosphere circulation indices. The Central Arctic Index (CAI), defined as the difference in sea level pressure between 84°N, 90°W and 84°N, 90°E, can explain 34–40% of the meridional displacement along the backward trajectories, and it can explain 27–40% of the zonal displacement along the forward trajectories. The winter Beaufort High (BH) anomaly can explain 18–27% of the zonal displacement. Under high positive CAI values or high negative winter BH anomalies, floes from the central Arctic tended to be advected out of the Arctic Ocean through Fram Strait or other marginal gateways. Conversely, under high negative CAI values or high positive winter BH anomalies, ice tended to become trapped within a region close to the North Pole or it drifted into the Beaufort Gyre region. The long‑term trend and spatial change in Arctic surface air temperature were more remarkable during the freezing season than the melt season because most energy from the lower troposphere is used to melt sea ice and warm the upper ocean during summer.

Research areas: Cryospheric Indicators
Spatiotemporal variability of surface velocities of monsoon temperate glaciers in the Kangri Karpo Mountains, southeastern Tibetan Plateau (2021)

Influenced by the Indian monsoon, the Kangri Karpo Mountains (KKM) of the southeastern Tibetan Plateau is the most humid part of the plateau, and one of the most important regions with numerous monsoon temperate glaciers. Glacier mass balance estimates have been strongly negative in the KKM over recent decades, but the spatiotemporal characteristics of surface velocity are poorly understood. Using phase-correlation feature tracking on Landsat images, this study estimates spatiotemporal variabilities of monsoon temperate glaciers for the period of 19882019. Results show that a significant slowdown was observed below an elevation of 4900 m, while an accelerated ice flow was found at an elevation of 49005800 m over the past 30 years. The trend of slowdown was 0.1 m a1 dec1 during 19882000, and then it increased to 0.5 m a1 dec1 during 20012019.

Research areas: Cryospheric Indicators
Surface melting over the Greenland ice sheet derived from enhanced resolution passive microwave brightness temperatures (1979–2019) (2021)

Abstract. Surface melting is a major component of the Greenland ice sheet surface mass balance, and it affects sea level rise through direct runoff and the modulation of ice dynamics and hydrological processes, supraglacially, englacially and subglacially. Passive microwave (PMW) brightness temperature observations are of paramount importance in studying the spatial and temporal evolution of surface melting due to their long temporal coverage (1979present) and high temporal resolution (daily). However, a major limitation of PMW datasets has been the relatively coarse spatial resolution, which has historically been of the order of tens of kilometers. Here, we use a newly released PMW dataset (37 GHz, horizontal polarization) made available through a NASA Making Earth System Data Records for Use in Research Environments (MeASUREs) program to study the spatiotemporal evolution of surface melting over the Greenland ice sheet at an enhanced spatial resolution of 3.125 km. We assess the outputs of different detection algorithms using data collected by automatic weather stations (AWSs) and the outputs of the Modele Atmospherique Regional (MAR) regional climate model. We found that sporadic melting is well captured using a dynamic algorithm based on the outputs of the Microwave Emission Model of Layered Snowpack (MEMLS), whereas a fixed threshold of 245 K is capable of detecting persistent melt. Our results indicate that, during the reference period from 1979 to 2019 (from 1988 to 2019), surface melting over the ice sheet increased in terms of both duration, up to 4.5 (2.9) d per decade, and extension, up to 6.9 % (3.6 %) of the entire ice sheet surface extent per decade, according to the MEMLS algorithm. Furthermore, the melting season started up to 4.0 (2.5) d earlier and ended 7.0 (3.9) d later per decade. We also explored the information content of the enhanced-resolution dataset with respect to the one at 25 km and MAR outputs using a semi-variogram approach. We found that the enhanced product is more sensitive to local-scale processes, thereby confirming the potential of this new enhanced product for monitoring surface melting over Greenland at a higher spatial resolution than the historical products and for monitoring its impact on sea level rise. This offers the opportunity to improve our understanding of the processes driving melting, to validate modeled melt extent at high resolution and, potentially, to assimilate these data in climate models.

Research areas: Cryospheric Indicators
Accelerated sea ice loss in the Wandel Sea points to a change in the Arctic's Last Ice Area (2021)

The Arctic Oceans Wandel Sea is the easternmost sector of the Last Ice Area, where thick, old sea ice is expected to endure longer than elsewhere. Nevertheless, in August 2020 the area experienced record-low sea ice concentration. Here we use satellite data and sea ice model experiments to determine what caused this record sea ice minimum. In our simulations there was a multi-year sea-ice thinning trend due to climate change. Natural climate variability expressed as wind-forced ice advection and subsequent melt added to this trend. In spring 2020, the Wandel Sea had a mixture of both thin andunusual for recent yearsthick ice, but this thick ice was not sufficiently widespread to prevent the summer sea ice concentration minimum. With continued thinning, more frequent low summer sea ice events are expected. We suggest that the Last Ice Area, an important refuge for ice-dependent species, is less resilient to warming than previously thought.

Research areas: Cryospheric Indicators
Comparison of Variations in Concentration of Arctic Marine Ice and Duration of Snow Period of Northern Eurasia under Conditions of Present-Day Climate According … (2018)

The short period variability of the duration of the occurrence of stable snow cover and the concentration of marine ice is revealed and compared for Northern Eurasia and the adjacent area of the Arctic Ocean against a background of multiannual variations in indices of atmospheric correlation in 20002015. The main principles of multiannual variations in the characteristics are determined. No correlation between the multiannual tendencies and interannual variability is found. Nonetheless, the calculation of the Fourier harmonics allowed identification of three five-year periods similar for all characteristics: 20002004, 20052009, and 20102014. The most intense variations of the duration of the occurrence of stable snow cover and concentration of marine ice from one five-year period to another are typical of the East European Platform in contrast to the noticeable but small variations for Siberia.

Research areas: Cryospheric Indicators, Atmospheric/Ocean Indicators
Assessing the performance of methods for monitoring ice phenology of the world's largest high Arctic lake using high-density time series analysis of Sentinel-1 data (2020)

Lake ice is a dominant component of Canadas landscape and can act as an indicator for how freshwater aquatic ecosystems are changing with warming climates. While lake ice monitoring through government networks has decreased in the last three decades, the increased availability of remote sensing images can help to provide consistent spatial and temporal coverage for areas with annual ice cover. Synthetic aperture radar (SAR) data are commonly used for lake ice monitoring, due to the acquisition of images in any condition (time of day or weather). Using Sentinel-1 A/B images, a high-density time series of SAR images was developed for Lake Hazen in Nunavut, Canada, from 20152018. These images were used to test two different methods of monitoring lake ice phenology: one method using the first difference between SAR images and another that applies the Otsu segmentation method. Ice phenology dates determined from the two methods were compared with visual interpretation of the Sentinel-1 images. Mean errors for the pixel comparison of the first difference method ranged 310 days for ice-on and ice-off, while average error values for the Otsu method ranged 210 days. Mean errors for comparisons of different sections of the lake ranged 015 days for the first difference method and 217 days for the Otsu method. This research demonstrates the value of temporally consistent image acquisition for improving the accuracy of lake ice monitoring.

Research areas: Cryospheric Indicators
Loss of floating glacier tongues from the Yelverton Bay region, Ellesmere Island, Canada (2019)

A total of eight floating glacier tongues have shrunk in area by >85% from the Yelverton Bay region of Northern Ellesmere Island since 1959, with unusually large losses since 2005. To better understand the causes of these losses, this study undertakes the first examination of ice tongue changes in this region, including an assessment of changes in surrounding marine ice (i.e. sea ice, sikussak and melange), and atmospheric and oceanographic forcings. From 1959 to 2017, the total ice tongue area decreased by 49.07 km2, with the majority of this loss occurring from 2005 to 2009 (34.68 km2). The loss of ice tongues since 2005 occurred when open water replaced multi-year landfast sea ice (MLSI) and first-year sea ice in the regions adjacent to the ice tongues. These changes were accompanied by an increase in mean annual mid-depth (i.e. 100 and 200 m) ocean temperatures from 0.29C from 1999 to 2005 to 0.67C from 2006 to 2012. Despite the recent return of ocean temperatures to below pre-2006 levels, atmospheric summer temperatures have continued to rise (+0.15C decade1 between 1948 and 2016), with open water continuing to occur. Without the sustained presence of MLSI in this region the ice tongues are unable to stabilize, making it unlikely that they will re-form in the current climate.

Research areas: Cryospheric Indicators
Impact of Shortened Winter Road Access on Costs of Forest Operations (2019)

A significant portion of the forest harvesting in the cooler regions of North America occurs in the winter when the ground is frozen and can support machine traffic. Climate change may influence the cost of forestry operations by reducing the period of winter access in those cold regions. In this study, we examined the impact of a shortened period of frozen ground conditions on logging operation and costs. To adapt to shorter period of frozen soil conditions, logging contractors might need to provide more machines and labor to complete logging in a shorter period of frozen conditions. The objectives were to calculate the costs of logging operations of a hypothetical forestry company in Alberta, Canada under two conditions: first, when the wood was hauled to the mill directly; and second, when part of the wood was hauled to satellite yards close to the logging area, thereby minimizing the annual number of idle hauling trucks. General Circulation Models were used to predict future winter weather conditions. Using the current type of harvesting machines and hauling directly to the mill, the unit cost of logging operations ($/m3) was projected to increase by an average of 1.6% to 2.5% in 2030s, 2.8% to 5.3% in the 2050s and 4.8% to 10.9% in the 2080s compared to the base year of 20152016. With use of satellite yards during the winter logging, the total logging cost will increase over direct haul, by 1.8% to 2.8% in the 2030s, 3.1% to 5.7% in the 2050s and 5.2% to 11.4% in the 2080s. Using satellite yards, however, will provide year-around employment for hauling truckers and more consistent and reliable hauling operations.

Research areas: Cryospheric Indicators
Parameter estimation and motion tracking of pack ice from FY-3/MERSI images (2020)

Abstract. A method to estimate the shape parameters and track the motion velocity of pack ice is presented. The method consists of sea ice recognition, pack ice extraction, parameters estimation and motion tracking. We try to estimate the shape parameters and track the motion velocity from FY-3/MERSI images of Fram strait, which were covered by cloud less than 30%. It found that the pack ice concentration significantly decreases faster than sea ice concentration. The two parameters indicate the distribution difference between sea ices and pack ices. The change of the perimeter and mean clamp diameter are obvious owing to they were sensitive to the edge of the pack ices. But the small change of roundness, convexity and width-height ratio indicate the shape similarity of pack ices in various size. More than 80% of the pack ices in the study region are tracked successfully by the proposed method. The resulting motion vectors in the overlapping zones are found to match well with the polar daily grid sea ice motion vectors provided by the National Snow and Ice Data Centre. The method can provide the actual motion vector of pack ices to improve the distribution and details of the grid-to-grid motion vectors.

Research areas: Cryospheric Indicators