scholarly journals Sediment plumes as a proxy for local ice-sheet runoff in Kangerlussuaq Fjord, West Greenland

2010 ◽  
Vol 56 (199) ◽  
pp. 813-821 ◽  
Author(s):  
Daniel McGrath ◽  
Konrad Steffen ◽  
Irina Overeem ◽  
Sebastian H. Mernild ◽  
Bent Hasholt ◽  
...  
Keyword(s):  
River Discharge ◽  
Water Storage ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
West Greenland ◽  
Meltwater Runoff ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

AbstractMeltwater runoff is an important component of the mass balance of the Greenland ice sheet (GrIS) and contributes to eustatic sea-level rise. In situ measurements of river runoff at the ˜325 outlets are nonexistent due to logistical difficulties. We develop a novel methodology using satellite observations of sediment plumes as a proxy for the onset, duration and volume of meltwater runoff from a basin of the GrIS. Sediment plumes integrate numerous poorly constrained processes, including meltwater refreezing and supra- and englacial water storage, and are formed by meltwater that exits the GrIS and enters the ocean. Plume characteristics are measured in Moderate Resolution Imaging Spectroradiometer (MODIS, band 1, 250 m) satellite imagery during the 2001-08 melt seasons. Plume formation and cessation in Kangerlussuaq Fjord, West Greenland, are positively correlated (r2 = 0.88, n = 5, p < 0.05; r2 = 0.93, n = 5, p < 0.05) with ablation onset and cessation at the Kangerlussuaq Transect automatic weather station S5 (490 ma.s.l., 6 km from the ice margin). Plume length is positively correlated (r2 = 0.52, n = 35, p < 0.05) with observed 4 day mean Watson River discharge throughout the 2007 and 2008 melt seasons. Plume length is used to infer instantaneous and annual cumulative Watson River discharge between 2001 and 2008. Reconstructed cumulative discharge values overestimate observed cumulative discharge values for 2007 and 2008 by 15% and 29%, respectively.

scholarly journals Consequences of the 2019 Greenland Ice Sheet Melt Episode on Albedo

2021 ◽  
Vol 13 (2) ◽  
pp. 227
Author(s):  
Arthur Elmes ◽  
Charlotte Levy ◽  
Angela Erb ◽  
Dorothy K. Hall ◽  
Ted A. Scambos ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Surface Albedo ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Energy Budget ◽  
Landsat 8 ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Seasonal Snow Cover

In mid-June 2019, the Greenland ice sheet (GrIS) experienced an extreme early-season melt event. This, coupled with an earlier-than-average melt onset and low prior winter snowfall over western Greenland, led to a rapid decrease in surface albedo and greater solar energy absorption over the melt season. The 2019 melt season resulted in significantly more melt than other recent years, even compared to exceptional melt years previously identified in the moderate-resolution imaging spectroradiometer (MODIS) record. The increased solar radiation absorbance in 2019 warmed the surface and increased the rate of meltwater production. We use two decades of satellite-derived albedo from the MODIS MCD43 record to show a significant and extended decrease in albedo in Greenland during 2019. This decrease, early in the melt season and continuing during peak summer insolation, caused increased radiative forcing of the ice sheet of 2.33 Wm−2 for 2019. Radiative forcing is strongly influenced by the dramatic seasonal differences in surface albedo experienced by any location experiencing persistent and seasonal snow-cover. We also illustrate the utility of the newly developed Landsat-8 albedo product for better capturing the detailed spatial heterogeneity of the landscape, leading to a more refined representation of the surface energy budget. While the MCD43 data accurately capture the albedo for a given 500 m pixel, the higher spatial resolution 30 m Landsat-8 albedos more fully represent the detailed landscape variations.

scholarly journals Evidence of meltwater retention within the Greenland ice sheet

2013 ◽  
Vol 7 (5) ◽  
pp. 1433-1445 ◽  
Author(s):  
A. K. Rennermalm ◽  
L. C. Smith ◽  
V. W. Chu ◽  
J. E. Box ◽  
R. R. Forster ◽  
...  
Keyword(s):  
River Discharge ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Cold Season ◽  
Global Ocean ◽  
Hydrologic Processes ◽  
Sheet Surface ◽  
Mass Losses ◽  
Meltwater Runoff

Abstract. Greenland ice sheet mass losses have increased in recent decades with more than half of these attributed to surface meltwater runoff. However, the magnitudes of englacial storage, firn retention, internal refreezing and other hydrologic processes that delay or reduce true water export to the global ocean remain less understood, partly due to a scarcity of in situ measurements. Here, ice sheet surface meltwater runoff and proglacial river discharge between 2008 and 2010 near Kangerlussuaq, southwestern Greenland were used to establish sub- and englacial meltwater storage for a small ice sheet watershed (36–64 km2). This watershed lacks significant potential meltwater storage in firn, surface lakes on the ice sheet and in the proglacial area, and receives limited proglacial precipitation. Thus, ice sheet surface runoff not accounted for by river discharge can reasonably be attributed to retention in sub- and englacial storage. Evidence for meltwater storage within the ice sheet includes (1) characteristic dampened daily river discharge amplitudes relative to ice sheet runoff; (2) three cold-season river discharge anomalies at times with limited ice sheet surface melt, demonstrating that meltwater may be retained up to 1–6 months; (3) annual ice sheet watershed runoff is not balanced by river discharge, and while near water budget closure is possible as much as 54% of melting season ice sheet runoff may not escape to downstream rivers; (4) even the large meltwater retention estimate (54%) is equivalent to less than 1% of the ice sheet volume, which suggests that storage in en- and subglacial cavities and till is plausible. While this study is the first to provide evidence for meltwater retention and delayed release within the Greenland ice sheet, more information is needed to establish how widespread this is along the Greenland ice sheet perimeter.

scholarly journals Automated remote sensing of sediment plumes for identification of runoff from the Greenland ice sheet

2012 ◽  
Vol 58 (210) ◽  
pp. 699-712 ◽  
Author(s):  
Andrew J. Tedstone ◽  
Neil S. Arnold
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Catchment Scale ◽  
Plume Area ◽  
Moderate Resolution ◽  
Control Procedures ◽  
Resolution Imaging ◽  
Satellite Microwave ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Microwave Imager

AbstractThe viability of employing sediment plumes emanating from outlets along the western margin of the Greenland ice sheet as indicators of runoff is assessed. An automated sediment plume quantification system based on daily 250 m Moderate Resolution Imaging Spectroradiometer (MODIS) band 1 reflectance imagery is developed. Coherent plumes are identified using spectral thresholds and polygon tracing. Validation employs imagery quality-control procedures and manual verification of plume areas. Outlets at land-terminating margins with wide and straight fjord geometries deliver the most accurate and consistent results. Plume area observations are also possible at marine-terminating margins with relatively static fronts and low proximal sea-ice concentrations. Variability in plume area is examined with reference to Special Satellite Microwave Imager (SSM/I)-derived daily melt extent at the hydrologic catchment scale. At annual timescales, plume areas tend to co-vary with surface melt extent, indicating that more mass is lost by runoff during years of extensive melting. Some synchronicity in plume areas from different catchments is apparent. At seasonal and daily timescales, plumes from individual outlets primarily relate to catchment-specific melting.

scholarly journals Snow Albedo Seasonality and Trend from MODIS Sensor and Ground Data at Johnsons Glacier, Livingston Island, Maritime Antarctica

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3569
Author(s):  
Calleja ◽  
Corbea-Pérez ◽  
Fernández ◽  
Recondo ◽  
Peón ◽  
...  
Keyword(s):  
Moving Average ◽  
Data Sets ◽  
Snow Albedo ◽  
Livingston Island ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Sky Conditions ◽  
Cloud Mask

The aim of this work is to investigate whether snow albedo seasonality and trend under all sky conditions at Johnsons Glacier (Livingston Island, Antarctica) can be tracked using the Moderate Resolution Imaging Spectroradiometer (MODIS) snow albedo daily product MOD10A1. The time span is from December 2006 to February 2015. As the MOD10A1 snow albedo product has never been used in Antarctica before, we also assess the performance for the MOD10A1 cloud mask. The motivation for this work is the need for a description of snow albedo under all sky conditions (including overcast days) using satellite data with mid-spatial resolution. In-situ albedo was filtered with a 5-day windowed moving average, while the MOD10A1 data were filtered using a maximum filter. Both in-situ and MOD10A1 data follow an exponential decay during the melting season, with a maximum decay of 0.049/0.094 day−1 (in-situ/MOD10A1) for the 2006–2007 season and a minimum of 0.016/0.016 day−1 for the 2009–2010 season. The duration of the decay varies from 85 days (2007–2008) to 167 days (2013–2014). Regarding the albedo trend, both data sets exhibit a slight increase of albedo, which may be explained by an increase of snowfall along with a decrease of snowmelt in the study area. Annual albedo increases of 0.2% and 0.7% are obtained for in-situ and MOD10A1 data, respectively, which amount to respective increases of 2% and 6% in the period 2006–2015. We conclude that MOD10A1 can be used to characterize snow albedo seasonality and trend on Livingston Island when filtered with a maximum filter.

scholarly journals Satellite-Based Estimation of Temporally Resolved Dust Radiative Forcing in Snow Cover

2016 ◽  
Vol 17 (7) ◽  
pp. 1999-2011 ◽  
Author(s):  
Steven D. Miller ◽  
Fang Wang ◽  
Ann B. Burgess ◽  
S. McKenzie Skiles ◽  
Matthew Rogers ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Radiative Forcing ◽  
Hydrological Cycle ◽  
Clear Sky ◽  
Operational Management ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Sky Conditions

Abstract Runoff from mountain snowpack is an important freshwater supply for many parts of the world. The deposition of aeolian dust on snow decreases snow albedo and increases the absorption of solar irradiance. This absorption accelerates melting, impacting the regional hydrological cycle in terms of timing and magnitude of runoff. The Moderate Resolution Imaging Spectroradiometer (MODIS) Dust Radiative Forcing in Snow (MODDRFS) satellite product allows estimation of the instantaneous (at time of satellite overpass) surface radiative forcing caused by dust. While such snapshots are useful, energy balance modeling requires temporally resolved radiative forcing to represent energy fluxes to the snowpack, as modulated primarily by varying cloud cover. Here, the instantaneous MODDRFS estimate is used as a tie point to calculate temporally resolved surface radiative forcing. Dust radiative forcing scenarios were considered for 1) clear-sky conditions and 2) all-sky conditions using satellite-based cloud observations. Comparisons against in situ stations in the Rocky Mountains show that accounting for the temporally resolved all-sky solar irradiance via satellite retrievals yields a more representative time series of dust radiative effects compared to the clear-sky assumption. The modeled impact of dust on enhanced snowmelt was found to be significant, accounting for nearly 50% of the total melt at the more contaminated station sites. The algorithm is applicable to regional basins worldwide, bearing relevance to both climate process research and the operational management of water resources.

scholarly journals GrSMBMIP: Intercomparison of the modelled 1980-2012 surface mass balance over the Greenland Ice sheet

2020 ◽  
Author(s):  
Xavier Fettweis ◽  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Climate Models ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Meltwater Runoff

&lt;p&gt;The Greenland Ice Sheet (GrIS) mass loss has been accelerating at a rate of about 20 +/- 10 Gt/yr&lt;sup&gt;2&lt;/sup&gt; since the end of the 1990's, with around 60% of this mass loss directly attributed to enhanced surface meltwater runoff. However, in the climate and glaciology communities, different approaches exist on how to model the different surface mass balance (SMB) components using: (1) complex physically-based climate models which are computationally expensive; (2) intermediate complexity energy balance models; (3) simple and fast positive degree day models which base their inferences on statistical principles and are computationally highly efficient. Additionally, many of these models compute the SMB components based on different spatial and temporal resolutions, with different forcing fields as well as different ice sheet topographies and extents, making inter-comparison difficult. In the GrIS SMB model intercomparison project (GrSMBMIP) we address these issues by forcing each model with the same data (i.e., the ERA-Interim reanalysis) except for two global models for which this forcing is limited to the oceanic conditions, and at the same time by interpolating all modelled results onto a common ice sheet mask at 1 km horizontal resolution for the common period 1980-2012. The SMB outputs from 13 models are then compared over the GrIS to (1) SMB estimates using a combination of gravimetric remote sensing data from GRACE and measured ice discharge, (2) ice cores, snow pits, in-situ SMB observations, and (3) remotely sensed bare ice extent from MODerate-resolution Imaging Spectroradiometer (MODIS). Our results reveal that the mean GrIS SMB of all 13 models has been positive between 1980 and 2012 with an average of 340 +/- 112 Gt/yr, but has decreased at an average rate of -7.3 Gt/yr&lt;sup&gt;2&lt;/sup&gt; (with a significance of 96%), mainly driven by an increase of 8.0 Gt/yr&lt;sup&gt;2&lt;/sup&gt; (with a significance of 98%) in meltwater runoff. Spatially, the largest spread among models can be found around the margins of the ice sheet, highlighting the need for accurate representation of the GrIS ablation zone extent and processes driving the surface melt. In addition, a higher density of in-situ SMB observations is required, especially in the south-east accumulation zone, where the model spread can reach 2 mWE/yr due to large discrepancies in modelled snowfall accumulation. Overall, polar regional climate models (RCMs) perform the best compared to observations, in particular for simulating precipitation patterns. However, other simpler and faster models have biases of same order than RCMs with observations and remain then useful tools for long-term simulations. It is also interesting to note that the ensemble mean of the 13 models produces the best estimate of the present day SMB relative to observations, suggesting that biases are not systematic among models. Finally, results from MAR forced by ERA5 will be added in this intercomparison to evaluate the added value of using this new reanalysis as forcing vs the former ERA-Interim reanalysis (used in SMBMIP).&amp;#160;&lt;/p&gt;

scholarly journals Seguimiento satelital de las condiciones océano-atmosféricas asociadas a los eventos de precipitación en Colombia durante el evento La Niña 2010–2011

2014 ◽  
pp. 123-134
Author(s):  
Martha Lucero Bastidas Salamanca ◽  
Apolinar Figueroa Casas
Keyword(s):  
La Niña ◽  
La Nina ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
La Niña 2010

La comprensión de la variabilidad climática es un tema de gran interés científico debido a que puede repercutir en las condiciones ambientales y socio-económicas de un país. Este estudio hace uso de datos satelitales para describir los eventos de precipitación ocurridos en el territorio colombiano durante el evento de La Niña 2010-2011 y registrados en estaciones meteorológicas costeras del Caribe. Se utilizaron datos de la temperatura de brillo de las nubes, medida por el Geostationary Operational Envirormental Satellite -GOES-12; datos de temperatura superficial del mar derivados de imágenes mensuales del Moderate Resolution Imaging Spectroradiometer – MODIS, y datos de precipitación intisituto de dos estaciones meteorológicas costeras (Cartagena y Santa Marta). Las imágenes satelitales GOES permitieron describir el evento La Niña 2010-2011 a partir de la identificación de nubes altas y complejos convectivos de mesoescala, los cuales se asocian a elevadas precipitaciones; mientras que las imágenes MODIS evidenciaron un comportamiento oceánico opuesto entre el Caribe colombiano, que exhibió anomalías positivas, y el Pacífico Oriental Tropical, que experimentó la influencia del evento y lo reflejó en anomalías negativas. Modelos lineales empleando datos satelitales de temperatura superficial del mar, in situ de precipitación y del Índice de Oscilación del Sur, revelaron que solamente para la estación ubicada en El Rodadero (Santa Marta), la precipitación fue explicada por la temperatura superficial del mar adyacente, mientras que el IOS no resultó significativo.

scholarly journals River inundation suggests ice-sheet runoff retention

2015 ◽  
Vol 61 (228) ◽  
pp. 776-788 ◽  
Author(s):  
Irina Overeem ◽  
Benjamin Hudson ◽  
Ethan Welty ◽  
Andreas Mikkelsen ◽  
Jonathan Bamber ◽  
...  
Keyword(s):  
River Discharge ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Indirect Evidence ◽  
Greenland Ice Sheet ◽  
Warming Trend ◽  
Global Ocean ◽  
Total Discharge

AbstractThe Greenland ice sheet is experiencing dramatic melt that is likely to continue with rapid Arctic warming. However, the proportion of meltwater stored before reaching the global ocean remains difficult to quantify. We use NASA MODIS surface reflectance data to estimate river discharge from two West Greenland rivers – the Watson River near Kangerlussuaq and the Naujat Kuat River near Nuuk – over the summers of 2000–12. By comparison with in situ river discharge observations, ‘inundation–discharge’ relations were constructed for both rivers. MODIS-based total annual discharges agree well with total discharge estimated from in situ observations (86% of summer discharge in 2009 to 96% in 2011 at the Watson River, and 106% of total discharge in 2011 to 104% in 2012 at the Naujat Kuat River). We find, however, that a time-lapse camera, deployed at the Watson River in summer 2012, better captures the variations in observed discharge, benefiting from fewer data gaps due to clouds. The MODIS-derived estimates indicate that summer discharge has not significantly increased over the last decade, despite a strong warming trend. Also, meltwater runoff estimates derived from the regional climate model RACMO2/GR for the drainage basins are higher than our reconstructions of river discharge. These results provide indirect evidence for a considerable component of water storage within the glacio-hydrological system.

scholarly journals Urban heat islands in the Arctic cities: an updated compilation of in situ and remote-sensing estimations

2021 ◽  
Vol 18 ◽  
pp. 51-57
Author(s):  
Igor Esau ◽  
Victoria Miles ◽  
Andrey Soromotin ◽  
Oleg Sizov ◽  
Mikhail Varentsov ◽  
...  
Keyword(s):  
Land Surface ◽  
Urban Infrastructure ◽  
Urban Heat Islands ◽  
The Arctic ◽  
Heat Islands ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Urban Heat ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. Persistent warm urban temperature anomalies – urban heat islands (UHIs) – significantly enhance already amplified climate warming in the Arctic. Vulnerability of urban infrastructure in the Arctic cities urges a region-wide study of the UHI intensity and its attribution to UHI drivers. This study presents an overview of the surface and atmospheric UHIs in all circum-Arctic settlements (118 in total) with the population larger than 3000 inhabitants. The surface UHI (SUHI) is obtained from the land surface temperature (LST) data products of the Moderate Resolution Imaging Spectroradiometer (MODIS) archive over 2000–2016. The atmospheric UHI is obtained from screen-level temperature provided by the Urban Heat Island Arctic Research Campaign (UHIARC) observational network over 2015–2018. Several other UHI studies are included for comparisons. The analysis reveals strong and persistent UHI during both summer and winter seasons. The annual mean surface UHI magnitudes vary from −0.6 ∘C (Hammerfest) to 4.3 ∘C (Murmansk). Thus, the observed UHI is likely an important climatic factor that must be included in future adjustment of urban construction, safety, and environmental quality codes.

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