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The amount and spatial extent of Greenland Sea (GS) ice are primarily controlled by the sea ice export across the Fram Strait (FS) and by local seasonal sea ice formation, melting, and sea ice dynamics. In this study, using satellite passive microwave sea ice observations, atmospheric and a coupled ocean-sea ice reanalysis system, TOPAZ4, we show that both the atmospheric and oceanic circulation in the Nordic Seas (NS) act in tandem to explain the SIC variability in the south-western GS. Northerly wind anomalies associated with anomalously low sea level pressure (SLP) over the NS reduce the sea ice export in the south-western GS due to westward Ekman drift of sea ice. On the other hand, the positive wind stress curl strengthens the cyclonic Greenland Sea Gyre (GSG) circulation in the central GS. An intensified GSG circulation may result in stronger Ekman divergence of surface cold and fresh waters away from the south-western GS. Both of these processes can reduce the freshwater content and weaken the upper-ocean stratification in the south-western GS. At the same time, warm and saline Atlantic Water (AW) anomalies are recirculated from the FS region to the south-western GS by a stronger GSG circulation. Under weakly stratified conditions, enhanced vertical mixing of these subsurface AW anomalies can warm the surface waters and inhibit new sea ice formation, further reducing the SIC in the south-western GS. [ABSTRACT FROM AUTHOR]

Substantial marine, terrestrial, and atmospheric changes have occurred over the Greenland region during the last century. Several studies have documented record‐levels of Greenland Ice Sheet (GrIS) summer melt extent during the 2000s and 2010s, but relatively little work has been carried out to assess regional climatic changes in other seasons. Here, we focus on the less studied cold‐season (i.e., autumn and winter) climate, tracing the long‐term (1873–2013) variability of Greenland's air temperatures through analyses of coastal observations and model‐derived outlet glacier series and their linkages with North Atlantic sea ice, sea surface temperature (SST), and atmospheric circulation indices. Through a statistical framework, large amounts of west and south Greenland temperature variance (up to r2 ~ 50%) can be explained by the seasonally‐contemporaneous combination of the Greenland Blocking Index (GBI) and the North Atlantic Oscillation (NAO; hereafter the combination of GBI and NAO is termed GBI). Lagged and concomitant regional sea‐ice concentration (SIC) and the Atlantic Multidecadal Oscillation (AMO) seasonal indices account for small amounts of residual air temperature variance (r2 < ~10%) relative to the GBI. The correlations between GBI and cold‐season temperatures are predominantly positive and statistically‐significant through time, while regional SIC conditions emerge as a significant covariate from the mid‐20th century through the conclusion of the study period. The inclusion of the cold‐season Pacific Decadal Oscillation (PDO) in multivariate analyses bolsters the air temperature variance explained by the North Atlantic regional predictors, suggesting the remote, background climate state is important to long‐term Greenland temperature variability. These findings imply that large‐scale tropospheric circulation has a strong control on surface temperature over Greenland through dynamic and thermodynamic impacts and stress the importance of understanding the evolving two‐way linkages between the North Atlantic marine and atmospheric environment in order to more accurately predict Greenland seasonal climate variability and change through the 21st century. [ABSTRACT FROM AUTHOR]

We provide an updated analysis of instrumental Greenland monthly temperature data to 2019, focusing mainly on coastal stations but also analysing ice‐sheet records from Swiss Camp and Summit. Significant summer (winter) coastal warming of ~1.7 (4.4)°C occurred from 1991–2019, but since 2001 overall temperature trends are generally flat and insignificant due to a cooling pattern over the last 6–7 years. Inland and coastal stations show broadly similar temperature trends for summer. Greenland temperature changes are more strongly correlated with Greenland Blocking than with North Atlantic Oscillation changes. In quantifying the association between Greenland coastal temperatures and Greenland Ice Sheet (GrIS) mass‐balance changes, we show a stronger link of temperatures with total mass balance rather than surface mass balance. Based on Greenland coastal temperatures and modelled mass balance for the 1972–2018 period, each 1°C of summer warming corresponds to ~(91) 116 Gt·yr−1 of GrIS (surface) mass loss and a 26 Gt·yr−1 increase in solid ice discharge. Given an estimated 4.0–6.6°C of further Greenland summer warming according to the regional model MAR projections run under CMIP6 future climate projections (SSP5‐8.5 scenario), and assuming that ice‐dynamical losses and ice sheet topography stay similar to the recent past, linear extrapolation gives a corresponding GrIS global sea‐level rise (SLR) contribution of ~10.0–12.6 cm by 2100, compared with the 8–27 cm (mean 15 cm) "likely" model projection range reported by IPCC in 2019 (SPM.B1.2). However, our estimate represents a lower limit for future GrIS change since fixed dynamical mass losses and amplified melt arising from both melt‐albedo and melt‐elevation positive feedbacks are not taken into account here. [ABSTRACT FROM AUTHOR]

An Empirical Orthogonal Function (EOF) variance analysis was performed to map in detail the spatiotemporal variability in individual stake mass-balances (ba) on Mittivakkat Gletscher (MG) - in a region where at present five out of ~20.000 glaciers have mass-balance observations. The EOF analysis suggested that observed ba was summarized by two modes: EOF1 and EOF2 represented 80% (significant) and 6% (insignificant) of the explained variance, respectively. EOF1 captured a decline in ba that was uniformly distributed in space at all stakes. The decline was correlated with albedo observations and air temperature observations from nearby stations. EOF2, however, described variations in ba that were heterogeneously distributed among stakes and associated with local slope and aspect. Low elevation stakes (~<400 m a.s.l.) showed relatively negative (out of phase) correlation and higher elevated stakes relatively positive (in phase) eigenvector correlation values with EOF2. Such relatively negative and positive eigenvector correlation values were present where the constituted of exposed glacier ice or snow cover, respectively. The results from this study show how EOF analyses can provide information on spatiotemporal patterns of glacier mass-balance. Understanding such detailed variabilities in mass-balance on a Greenlandic glacier is of interest because a fifth of the Arctic contribution from glaciers and ice caps to sea-level rise originates from Greenland. [ABSTRACT FROM AUTHOR]

Empirically based studies of glacier meteorology, especially for the Southern Hemisphere, are relatively sparse in the literature. Here, we use an innovative network of highly portable, low-cost thermometers to report on high-frequency (1-min time resolution) surface air temperature fluctuations and lapse rates (LR) in a ~800-m elevational range (from 3,675 to 4,492 m a.s.l.) across the glacier Olivares Gamma in the central Andes, Chile. Temperatures were measured during an intense field campaign in late Southern summer, 19–27 March 2015, under varying weather conditions. We found a complex dependence of high-frequency LR on time of day, topography, and wider meteorological conditions, with hourly temperature variations during this week that were probably mainly associated with short- and long-wave radiation changes and not with wind speed/direction changes. Using various pairs of sites within our station network, we also analyze spatial variations in LR. Uniquely in this study, we compare temperatures measured at heights of 1-m and 2-m above the glacier surface for the network of five sites and found that temperatures at these two heights occasionally differed by more than ±4°C during the early afternoons, although the mean temperature difference is much smaller (~0.3°C). An implication of our results is that daily, hourly, or even monthly averaged LR may be insufficient for feeding into accurate melt models of glacier change, with the adoption of subhourly (ideally 1–10-min) resolution LR likely to prove fruitful in developing new innovative high-time-resolution melt modelling. Our results are potentially useful as input LR for local glacier melt models and for improving the understanding of lapse rate fluctuations and glacier response to climate change. [ABSTRACT FROM AUTHOR]

ABSTRACT Glacier surface mass balance ( SMB) observations for the Andes Cordillera are limited and therefore estimates of the SMB contribution to sea-level rise are highly uncertain. Here (in Part 3), we simulate glacier surface meteorological and hydrological conditions and trends for the Andes Cordillera (1979/80-2013/14; 35 years), covering the tropical latitudes in the north down to the sub-polar latitudes in the far south, including the Northern Patagonia Icefield ( NPI) and Southern Patagonia Icefield ( SPI). Surface meteorological conditions and heat- and mass-transfer processes were simulated for all glaciers having an area equal to or greater than 0.5 km2. SnowModel - a fully integrated energy balance, blowing-snow distribution, multi-layer snowpack, and runoff routing model - was used to simulate glacier SMBs for the Andes Cordillera. The Randolph Glacier Inventory ( RGI; v. 4.0) and NASA Modern-Era Retrospective Analysis for Research and Applications ( MERRA) products, downscaled in SnowModel, allowed us to conduct relatively high-resolution (1-km horizontal grid; 3-h time step) simulations of glacier air temperature, precipitation, sublimation, evaporation, runoff, and SMB. These simulated glacier SMBs were verified against both independent direct observed annual glacier SMB and satellite gravimetry and altimetry derived SMB, indicating a good agreement. For Andes glaciers, the 35-year mean annual SMB was found to be −1.13 m water equivalent (w.e.), while the cumulative SMB was −39.6 m w.e., which is equal to a cumulative SMB contribution of 3.4 mm sea-level equivalent ( SLE) (∼0.1 mm SLE per year). However, for both NPI and SPI, the mean SMB was positive (where likely calving explains why geodetic estimates are negative). For the Andes Cordillera, the simulated mean glacier-specific runoff was 41 L s−1 km−2, while for NPI and SPI it was 213 and 198 L s−1 km−2, respectively, indicating available water resources from NPI and SPI. [ABSTRACT FROM AUTHOR]

ABSTRACT The spatio-temporal freshwater river run-off pattern from individual basins, including their run-off magnitude and change (1979/1980-2013/2014), was simulated for the Andes Cordillera west of the Continental Divide in an effort to understand run-off variations and freshwater fluxes to adjacent fjords, Pacific Ocean, and Drake Passage. The modelling tool SnowModel/HydroFlow was applied to simulate river run-off at 3-h intervals to resolve the diurnal cycle and at 4-km horizontal grid increments using atmospheric forcing from NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) data sets. Simulated river run-off hydrographs were verified against independent observed hydrographs. For the domain, 86% of the simulated run-off originated from rain, 12% from snowmelt, and 2% from ice melt, whereas for Chile, the water-source distribution was 69, 24, and 7%, respectively. Along the Andes Cordillera, the 35-year mean basin outlet-specific run-off (L s−1 km−2) showed a characteristic regional hourglass shape pattern with highest run-off in both Colombia and Ecuador and in Patagonia, and lowest run-off in the Atacama Desert area. An Empirical Orthogonal Function analysis identified correlations between the spatio-temporal pattern of run-off and flux to the El Niño Southern Oscillation Index and to the Pacific Decadal Oscillation. [ABSTRACT FROM AUTHOR]

ABSTRACT Snow cover presence, duration, properties, and water amount play a major role in Earth's climate system through its impact on the surface energy budget. Snow cover conditions and trends (1979-2014) were simulated for South America - for the entire Andes Cordillera. Recent data sets and SnowModel developments allow relatively high-resolutions of 3-h time step and 4-km horizontal grid increment for this domain. US Geological Survey's Global Multi-resolution Terrain Elevation Data 2010 topography, Global Land Cover ( GlobCover), Randolph Glacier Inventory (v. 4.0) glacier, and NASA modern-era retrospective analysis for research and applications data sets were used to simulate first-order atmospheric forcing (e.g. near-surface air temperature and precipitation, including the fraction of precipitation falling as snow) and terrestrial snow characteristics (e.g. snow cover days, snow water equivalent depth, and snow density). Simulated snow conditions were verified against moderate-resolution imaging spectroradiometer-derived snow cover extent and 3064 individual direct observations of snow depths. Regional variability in mean annual air temperature occurred: positive trends in general were seen in the high Andes Cordillera, and negative trends at relatively lower elevations both east and west of the Cordillera. Snow precipitation showed more heterogeneous patterns than air temperature due to the influence from atmospheric conditions, topography, and orography. Overall, for the Cordillera, much of the area north of 23°S had a decrease in the number of snow cover days, while the southern half experienced the opposite. The snow cover extent changed ∼−15% during the simulation period, mostly between the elevations of ∼3000 and 5000 m above sea level (a.s.l.). However, below 1000 m a.s.l. (in Patagonia) the snow cover extent increased. The snow properties varied over short distances both along and across the Andes Cordillera. [ABSTRACT FROM AUTHOR]

ABSTRACT Snow cover extent, duration, and properties were simulated (1979/1980-2013/2014) for the Rio Olivares Basin (548 km2) in central Chilean Andes, in an effort to understand conditions and trends (linear) at a basin scale. The National Aeronautics and Space Administration Modern-Era Retrospective Analysis for Research and Applications products, together with the snow modelling software package SnowModel allowed simulations of first-order atmospheric forcings (mean annual air temperature ( MAAT) and water-equivalent precipitation) and terrestrial snow features (snow cover extent, duration, snow water-equivalent depth, snow density, and runoff generated from snow melt). Simulated snow cover extent and depletion curves were verified against Moderate Resolution Imaging Spectroradiometer-derived snow cover data. For the Rio Olivares Basin, MAAT was −2.9 ± 0.6 °C with a mean 0° isotherm at 3325 m a.s.l. The greatest temporal and spatial changes in temperature over the 35-year period occurred in January and at the highest elevations, respectively. Mean annual precipitation was 1.86 ± 0.60 m w.e., indicating an increase in precipitation of ∼0.1 m w.e. 100 m−1 increase in elevation. On average, ∼90% of the basin precipitation fell as snow, varying from 70% at ∼2600 m a.s.l., to 95% at ∼4200 m a.s.l. In 20 out of 35 years the snow cover extent went to 0% (no basin snow cover) by end-of-summer (during March), and the snow duration increased on average by ∼10 days 100 m−1 increase in elevation. Approximately 85% of the basin outlet freshwater runoff originated from snowmelt, making snowmelt a dominant contributor to water resources. Snowmelt-derived basin runoff was dominated by variability in snow precipitation rather than by variability in MAAT. [ABSTRACT FROM AUTHOR]

For the Andes Cordillera, where observed mass-balance records are sparse, long-term glacier velocity measurements potentially represent a useful tool for assessing glacier health. Utilising manual and automatic feature-tracking techniques applied to Corona, Landsat and ASTER satellite imagery, this paper presents surface velocity fluctuations for Glaciar Universidad between 1967 and 1969, and 1985 and 2015, the longest such time series available for the Andes Cordillera, outside Patagonia. This time series reveals an increase in the surface velocities of the main glacier trunk between 1967 and 1987 (~90%) followed by a deceleration between 1987 and 2015 (~80%), with ice velocities observed between 2014 and 2015 possibly representing a 48 a low. In response to the surface velocity fluctuations, the glacier front advanced between 1985 and 1992 (cumulative change of 137 ± 14 m), and again to a lesser magnitude during the 1996–98 and 2004–08 periods. Although having exhibited possible surge behaviour during the 1940s, the synchrony of the glacier changes presented for Glaciar Universidad with those reported for nearby glaciers, suggests that this glacier is responding to climatic trends. If the above scenario is true, the results indicate a general pattern of increasingly negative glacier mass-balance conditions since the late 1980s. [ABSTRACT FROM AUTHOR]

To improve our knowledge of glacier area changes in the central Chilean and Argentinean Andes (32°9'S-33°4'S), two new glacier inventories from 1989 to 2013/14 are compared with a reinterpreted inventory from 1955. Comparisons show glacier area retreat of 30 ± 3% since 1955, decreasing from 134 to 94 km² in 2013/14, whilst the annual rate of area loss showed a small increase (insignificant) between the periods of 1955-1989 and 1989-2013/14. Separate analysis of the 1989 and 2013/14 inventories, including a larger sample, revealed a higher rate of glacier change compared with the smaller samples of these inventories. Additionally, an analysis at ~5 year intervals for six major glaciers (1955-2013) indicates large variability in response times and area loss magnitudes. Glacier Olivares Alfa, for example, lost 63% of its ice area, while the Juncal Norte Glacier lost only 10% (1955-2013). The findings from this study improve our current knowledge base concerning widespread glacier decline in the southern Andes, and furthers monitoring efforts in this poorly described region of the world, a region containing vital water resources for populated areas in South America. [ABSTRACT FROM AUTHOR]

Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was -14.68±0.18‰ during the peak flow period. A hydrograph separation analysis revealed that the ice melt component constituted 82±5% of the total run-off and dominated the observed variations during peak flow in August 2004. The snowmelt component peaked between 10:00 and 13:00 local time, reflecting the long travel time and an inefficient distributed subglacial drainage network in the upper part of the glacier. At the Kuannersuit Glacier river on the island Qeqertarsuaq in west Greenland, the δ18O characteristics were examined after the major 1995-1998 glacier surge event. The mean annual δ18O was -19.47±0.55 ‰. Despite large spatial variations in the δ18O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier in the post-surge years. This is likely a consequence of a tortuous subglacial drainage system consisting of linked cavities, which formed during the surge event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers and ice caps (between -23.0 and -13.7 ‰) and the GrIS (between -29.9 and -23.2 ‰). This study demonstrates that water isotope analyses can be used to obtain important information on water sources and the subglacial drainage system structure that is highly desired for understanding glacier hydrology. [ABSTRACT FROM AUTHOR]

Albedo is one of the parameters that govern energy availability for snow and ice surface ablation, and subsequently the surface mass balance conditions of temperate glaciers and ice caps (GIC). Here, we document snow and ice albedo changes for Mittivakkat Gletscher (MG) in Southeast Greenland (2000-2013), for which an 18-year record of direct surface mass balance measurements exists. The MODerate Imaging Spectroradiometer (MODIS MCD43A3) albedo product was used to study MG's snow and ice albedo, evaluated against supraglacial automatic weather station (AWS) observations. In general, by the end of the mass balance year (EBY), MG's AWS observed bare ice albedo reached ∼0.3 only just exceeding values observed for proglacial bedrock ( ∼0.2). The analysis reveals negative mean trends in the MODIS-derived MG EBY albedo for the period 2000-2013 with a significant decline in mean glacier-wide albedo of 0.10. The greatest decline in albedo, of 0.25, occurred near the equilibrium line altitude (ELA), an important surface cover and albedo transitional zone. The EBY albedo correlates significantly with ELA and net winter and summer glacier mass balance records. [ABSTRACT FROM AUTHOR]

The distribution of terrestrial surface runoff to Ilulissat Icefjord, west Greenland, is simulated for the period 2009-13 to better emphasize the spatiotemporal variability in freshwater flux and the link between runoff spikes and observed hydrographic conditions at the Greenland Ice Sheet tidewater glacier margins. Runoff model simulations were forced with automatic weather station data and verified against snow water equivalent depth, equilibrium line altitude, and quasi-continuous salinity and temperature observations obtained by ringed seals. Instrumented seals provide a novel platform to examine the otherwise inaccessible waters beneath the dense ice mélange within the first 0-10 km of the calving front. The estimated mean freshwater flux from land was 70.6 ± 4.2 km3 yr−1, with an 85% contribution of ice discharge from Jakobshavn Isbrae (also known as Sermeq Kujalleq), 14% from runoff, and the remaining 1% from precipitation on the fjord surface area, subglacial geothermal melting, and frictional melting due to basal ice motion. Runoff was simulated to be present from May to November and to vary spatially according to glacier cover and individual catchment size. Salinity and temperature observations correlate (significantly) with simulated runoff for the upper part of both the main fjord and southern fjord arm. Also, at the tidewater glacier margins in the northern and southern arm of Ilulissat Icefjord, salinity changes in the upper water column (upper 50 m) are significant after temporal spikes in runoff during late summer, while small-amplitude runoff variability during the recession of runoff did not create a clear signal in observed salinity variability. Also, in the southern arm near the glacier margin (between 100- and 150-m depth), the heterogeneous distribution in salinity could be because of the mixing of meltwater going upward from passing the grounding line. The effect of runoff spikes on observed salinity is less pronounced near the ice margin of Jakobshavn Isbrae than in the north and south arms. [ABSTRACT FROM AUTHOR]

ABSTRACT Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series compiled from coastal meteorological stations in Greenland and Greenland Ice Sheet ( GrIS) ice cores (including three new ice core records from ACT11D, Tunu2013, and Summit2010). The dataset covers the period from 1890 to 2012, a period of climate warming. For approximately the first decade of the new millennium (2001-2012) minimum and maximum mean annual precipitation conditions are found in Northeast Greenland (Tunu2013 c. 120 mm water equivalent (w.e.) year−1) and South Greenland (Ikerasassuaq: c. 2300 mm w.e. year−1), respectively. The coastal meteorological stations showed on average increasing trends for 1890-2012 (3.5 mm w.e. year−2) and 1961-2012 (1.3 mm w.e. year−2). Years with high coastal annual precipitation also had a: (1) significant high number of precipitation days ( r2 = 0.59); and (2) high precipitation intensity measured as 24-h precipitation ( r2 = 0.54). For the GrIS the precipitation estimated from ice cores increased on average by 0.1 mm w.e. year−2 (1890-2000), showing an antiphase variability in precipitation trends between the GrIS and the coastal regions. Around 1960 a major shift occurred in the precipitation pattern towards wetter precipitation conditions for coastal Greenland, while drier conditions became more prevalent on the GrIS. Differences in precipitation trends indicate a heterogeneous spatial distribution of precipitation in Greenland. An Empirical Orthogonal Function analysis reveals a spatiotemporal cycle of precipitation that is linked instantaneously to the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation and with an ∼6 years lag time response to the Greenland Blocking Index. [ABSTRACT FROM AUTHOR]

ABSTRACT We use observed air temperature data series from 14 meteorological stations in coastal Greenland (located all around the Greenland Ice Sheet) for 1960-2010, where long-term records for five of the stations extend back to 1890, to illustrate the annual and monthly temporal and spatial distribution of temperature extremes, with the main focus on the latest decade 2001-2010 (2000s). We find that the 2000s had the highest number of mean annual air temperature ( MAAT) warm extremes, and the 1890s the highest number of cold extremes, and that a high (low) positive North Atlantic Oscillation ( NAO) Index equals a high number of cold (warm) extreme events. For the 2000s the number of warm extremes was significantly higher by around 50% than the number in the 1940s (the early twentieth century warm period): the latter being the decade with the second highest occurrence of MAAT warm extremes. Since 1960, based on MAAT the number of cold extremes has overall decreased on the decadal timescale, besides a peak in 1980s, while warm extremes have increased, leading to a higher occurrence of extremes (cold plus warm extremes): an almost similar pattern occurred for monthly mean temperatures and monthly mean daily maximum and minimum temperature datasets. Furthermore, a division of Greenland into east and west sectors shows that the occurrence of cold (warm) extremes was more pronounced in the East than in the West in the 1960s and 1970s (mid-1980s to the 2000s). [ABSTRACT FROM AUTHOR]

ABSTRACT The NASA announcement of record surface melting of the Greenland ice sheet in July 2012 led us to examine the atmospheric and oceanic climatic anomalies that are likely to have contributed to these exceptional conditions and also to ask the question of how unusual these anomalies were compared to available records. Our analysis allows us to assess the relative contributions of these two key influences to both the extreme melt event and ongoing climate change. In 2012, as in recent warm summers since 2007, a blocking high pressure feature, associated with negative NAO conditions, was present in the mid-troposphere over Greenland for much of the summer. This circulation pattern advected relatively warm southerly winds over the western flank of the ice sheet, forming a 'heat dome' over Greenland that led to the widespread surface melting. Both sea-surface temperature and sea-ice cover anomalies seem to have played a minimal role in this record melt, relative to atmospheric circulation. Two representative coastal climatological station averages and several individual stations in south, west and north-west Greenland set new surface air temperature records for May, June, July and the whole (JJA) summer. The unusually warm summer 2012 conditions extended to the top of the ice sheet at Summit, where our reanalysed (1994-2012) DMI Summit weather station summer (JJA) temperature series set new record high mean and extreme temperatures in 2012; 3-hourly instantaneous 2-m temperatures reached an exceptional value of 2.2°C at Summit on 11 July 2012. These conditions translated into the record observed ice-sheet wide melt during summer 2012. However, 2012 seems not to be climatically representative of future 'average' summers projected this century. [ABSTRACT FROM AUTHOR]

The article presents a study which documents changes for Mittivakkat Gletscher, which is the peripheral glacier in Greenland. It says that the study attributed the changes to summer warming and lower winter snow accumulation with low vertical strain of the elevation change due to surface mass balance (SMB). It states that Mittivakkat Gletscher summer surface velocities were up to 160% higher during the peak velocity and 50%-60% above winter values.

The article presents a study on the use of transient snowline (TSL)variations on two Arctic glaciers to identify snow ablation rate, equilibrium-line altitude (ELA), accumulation-area ratio (AAR), and net mass balance. It uses TSL observations at Lemon Creek Glacier (LCG) in Alaska and Mittivakkat Gletshcer (MG) to explore the consistency of TSL and snow ablation rate. Results show that both glaciers the estimated ELA and AAR were in accordance with annual fieldwork observations.

An automated layer counting technique is developed to estimate the chronology of a marine sediment core and this technique is validated with Pb210 chronology. The marine sediment core was sampled in front of the delta of Mittivakkat Glacier meltwater river in the Sermilik Fjord, SE Greenland, and is a proxy of the sediment delivery from a glacial drainage basin to a fjord. The estimated time series was based on automatic lamination detection (varves) on a line scan of the core using gray scale intensities, and covered the last two centuries. The estimated time series of sediment accumulation rates was coupled to modelled runoff from the Mittivakkat Glacier and compared with local climatic parameters (air temperature and precipitation) and with the Atlantic Multidecadal Oscillation (AMO) index. Maxima in the sediment accumulation rate at the bottom of the side-fjord, about 1 km from the delta, mostly depended on glacier ablation and consequently on changes in river runoff, which were initiated by the air temperature. This was especially the case during transition from colder periods towards warmer, where short-lived maxima in sediment accumulation rates were followed by lower rates, even though the temperature remained high. This suggested a quite rapid glacial response to changes in climatic forcing, and/or a hysteresis effect, where sediment stored in the glacier/valley system was evacuated soon after a temperature dependent increase in discharge. The air temperature was in turn controlled by the AMO index. [ABSTRACT FROM AUTHOR]

Correlation analysis of Greenland coastal weather station temperatures against the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) indices for the summer season (when Ice Sheet melt and runoff occur) reveals significant temporal variations over the last 100 years, with periods of strongest correlations in the early twentieth century and during recent decades. During the mid-twentieth century, temperature changes at the stations are not significantly correlated with these circulation indices. Greenland coastal summer temperatures and Greenland Ice Sheet (GrIS) runoff since the 1970s are more strongly correlated with the Greenland Blocking Index (GBI) than with the NAO Index (NAOI), making the GBI a potentially useful predictor of ice-sheet mass balance changes. Our results show that the changing strength of NAOI-temperature relationships found in boreal winter also extends to summer over Greenland. Greenland temperatures and GrIS runoff over the last 30-40 years are significantly correlated with AMO variations, although they are more strongly correlated with GBI changes. GrIS melt extent is less significantly correlated with atmospheric and oceanic index changes than runoff, which we attribute to the latter being a more quantitative index of Ice Sheet response to climate change. Moreover, the four recent warm summers of 2007-2010 are characterised by unprecedented high pressure (since at least 1948-the start of the NCEP/NCAR reanalysis record) in the tropospheric column. Our results suggest complex and changing atmospheric forcing conditions that are not well captured using the NAO alone, and support theories of an oceanic influence on the recent increases in Greenland temperatures and GrIS runoff. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The freshwater runoff from the glaciated and snow-covered Sermilik Fjord catchment, SE Greenland, was estimated at annual resolution for the period 1900–2008 and at decadal resolution for the past four millennia. Our simulations were forced with available meteorological station data (1900–2008) and Greenland ice core estimated temperature data (1899 bc–ad 1980) from Dye3 and GISP2. Time series of estimated ice discharge (2000–2009) for the three major outlet glaciers Helheim, Fenris, and Midgård indicate that 53–74% of the ice discharge variations could be explained by variations in areally averaged glacier terminus surface (supraglacial) runoff. Based on these data and together with calculated subglacial geothermal and frictional melting as well as net precipitation for the fjord area, the Sermilik Fjord freshwater flux was deduced for the period 1900–2008. Our simulations indicated that during the last century surface freshwater runoff has equaled 13% of the Sermilik Fjord average freshwater flux of 33.0±5.7×109 m3/yr, covering a periodic runoff variation of 20 years. Ice discharge has accounted for 81%, with 63% of the freshwater flux originated from the Helheim glacier. This indicates that the Helheim outlet glacier plays a dominant role as a freshwater source to both Sermilik Fjord and ultimately the Irminger Sea. For the palaeorecords of the last 4000 years, simulated surface runoff has averaged 4.4±0.2×109 m3/yr. A very weak decreasing trend in runoff over the last 4 k years (1899 bc–ad 1980) is presumably associated with the general insolation-generated Northern Hemisphere cooling since the Holocene Thermal Maximum. Our simulations furthermore indicated centennial- to submillennial-scale variations in surface runoff concurrent with the well-known climate episodes such as the ‘Roman Warm Period’, the ‘Dark Ages Cold Period’, the ‘Medieval Climate Anomaly’, and the ‘Little Ice Age’. During the ‘Little Ice Age’, e.g., the average surface runoff was about 0.7×109 m3/yr lower than today, while the increase in runoff for the Modern Warming, since the late 1800s, was the second strongest and fastest for the last 4 k years. [ABSTRACT FROM PUBLISHER]

The article focuses on a study about the extent and trends in ice sheet surface melt in Greenland from 1960 to 2010. It cites the Greenland ice sheet (GrIS) as the largest reservoir of permanent snow and ice in the Northern Hemisphere, adding that it tends to be highly sensitive to changes in climate and has posted record surface melt extent in 2007 and 2010. Factors behind the importance of the extent and duration of surface melting are given, one is the production of substantial differences in surface albedo and energy and moisture balances as a result of melting. Findings indicate a decline in the melt period from 1960 to 1972 followed by record melt extent in 2010 during which melt duration at the southwestern and western margins exceeded the average.

The article discusses a study on the methodology for estimating the onset, duration and volume of meltwater runoff from a localized basin of the Greenland ice sheet (GrlS) using satellite observations of sediment plume length in the Russell Glacier-Watson River-Kangerlussuaq Fjord system. Moderate Resolution Imaging Spectroradiometer (MODIS) was used to generate satellite imagery. It mentions the influence of wind stress on the structure and distribution of buoyant coastal plumes over daily and seasonal timescales. The Watson River and the Ørkendalen river are cited as the major river systems that transport meltwater from the GrlS into the fjord. It concludes that plume formation is an alternative metric to the melt season to estimate runoff onset and duration.

The article discusses the study which examines the temporal variability of surface snow and glacier melt flux and runoff at the ablation area of Jakobshavn Isbræ, West Greenland. It states the modeled interannual runoff variability has resulted to a value that yields a cumulative runoff at the Jakobshavn Glacier terminus towards the freshwater flux. It notes that the surface runoff forms a minor part of the overall Jakobshavn freshwater flux that originates from the surface runoff which has a moisture that changes phases into solid, liquid, and vapor throughout the year as part of the various physical processes.

The article presents a study that aims to present the observed 2007 and 2008 runoff and suspended sediment load from the Greenland ice sheet (GrIS), a drainage area in Kangerlussuaq, West Greenland. It states that the observations have value to obtain knowledge on terrestrial freshwater and sediment output from part of the GrIS and the strip of land between the ice sheet and the ocean. It adds that the discharge and sediment load shows a decrease of -25 percent in runoff and -40 percent in sediment load from 2007 and 2008 in response to a decrease in the summer accumulated number of positive degree-days.

The article presents a study which measures the surface mass balance (SMB) of the 1995-2007 Greenland Ice Sheet (GrIs), including freshwater flux with the use of the state-of-the-art snow evolution modeling system called SnowModel. It cites that model inputs from meteorological observations from 26 meteorological stations located on the GrIS and in costal Greenland were used. Further, the study aims to improve the quantitative understanding of the GrIS surface melt extent in 2007.

The article presents a study on the terrestrial flux of freshwater runoff from East Greenland to the Greenland-Iceland-Norwegian (GIN) Seas for the periods 1999-2004 and 2071-2100. It states that this study is grounded on vvalidation and calibration of SnowModel with in situ data from the only two long-term permanent automatic meteorological and hydrometric monitoring catchments in East Greenland, which are the Mittivakkat Glacier catchment in Southeast Greenland and the Zackenberg Glacier catchment in Northeast Greenland. It mentions that the freshwater runoff from the Greenland Ice Sheet (GrIS) is more than twice from the present's values, which is based hugely on increasing air temperature rather than from changes in net precipitation.

The article presents the study which quantifies the annual discharge from the snow and glacierized Zackenberg River drainage basin in northeast Greenland. It aims to simulate the time evolution of catchment runoff using the combined hydrologic modelling systems, MIKE SHE and SnowModel. The combined model only include first-order effects of climate change. For the period 2071-2100, the future climate scenarios indicated a mean annual Zackenberg runoff about 1.5 orders of magnitude greater than from 1997-2005. It is mainly base on changes in negative glacier net mass balance.