scholarly journals Impact of Cloud Physics on the Greenland Ice Sheet Near‐Surface Climate: A Study With the Community Atmosphere Model

2020 ◽  
Vol 125 (7) ◽  
Author(s):  
Jan T. M. Lenaerts ◽  
Andrew Gettelman ◽  
Kristof Van Tricht ◽  
Leo Kampenhout ◽  
Nathaniel B. Miller
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Cloud Physics ◽  
Near Surface ◽  
Community Atmosphere Model ◽  
Surface Climate ◽  
Atmosphere Model

scholarly journals Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation

2014 ◽  
Vol 8 (2) ◽  
pp. 801-814 ◽  
Author(s):  
J. T. M. Lenaerts ◽  
C. J. P. P. Smeets ◽  
K. Nishimura ◽  
M. Eijkelboom ◽  
W. Boot ◽  
...  
Keyword(s):  
High Frequency ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Size Distributions ◽  
Near Surface ◽  
Drifting Snow ◽  
Surface Climate ◽  
Meteorological Observations ◽  
Regional Atmospheric Climate Model

Abstract. This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency snow particle counter (SPC) observations at ~ 1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the horizontal snow transport at this level, which can be related to an overestimation of saltation and the typical size of drifting snow particles.

scholarly journals Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation

2014 ◽  
Vol 8 (1) ◽  
pp. 21-53 ◽  
Author(s):  
J. T. M. Lenaerts ◽  
C. J. P. P. Smeets ◽  
K. Nishimura ◽  
M. Eijkelboom ◽  
W. Boot ◽  
...  
Keyword(s):  
High Frequency ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Size Distributions ◽  
Near Surface ◽  
Drifting Snow ◽  
Surface Climate ◽  
Meteorological Observations ◽  
Regional Atmospheric Climate Model

Abstract. This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency Snow Particle Counter (SPC) observations at ~1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short-lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the typical size of drifting snow particles, as well as the horizontal snow transport at this level.

scholarly journals Long-term surface energy balance of the western Greenland ice sheet and the role of large-scale circulation variability

2020 ◽  
Author(s):  
Baojuan Huai ◽  
Michiel R. van den Broeke ◽  
Carleen H. Reijmer
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climate Variables ◽  
Large Scale Circulation ◽  
Near Surface ◽  
Surface Climate

Abstract. We present the surface energy balance (SEB) of the west Greenland ice sheet (GrIS), using an energy balance model forced with hourly observations from nine automatic weather stations (AWS) along two transects: the K-transect with seven AWS in the southwest and the T-transect with two AWS in the northwest. Modeled and observed surface temperatures for non-melting conditions agree well, with RMSEs of 1.1–1.6 K, while reasonable agreement is found between modeled and observed 10-day cumulative ice melt. Absorbed shortwave radiation (Snet) is the main energy source for melting (M), followed by the sensible heat flux (Qh). The multi-year average seasonal cycle of SEB components show that Snet and M peak in July at all AWS. The turbulent fluxes of sensible (Qh) and latent heat (Ql) decrease significantly with elevation, and the latter becomes negative at higher elevations, partly offsetting Qh. Average June, July, August (JJA) albedo values are  0.7 for the higher stations. The near-surface climate variables and surface energy fluxes from reanalysis products ERA-interim, ERA5 and the regional climate model RACMO2.3 were compared to the AWS values. The newer ERA5 product only significantly improves on ERA-interim for albedo. The regional model RACMO2.3, which has higher resolution (5.5 km) and a dedicated snow/ice module, unsurprisingly outperforms the re-analyses for (near-) surface climate variables, but the reanalyses are indispensable to detect dependencies of west Greenland climate and melt on large-scale circulation variability. We correlate ERA5 with the AWS data to show a significant positive correlation of western GrIS summer surface temperature and melt with the Greenland Blocking Index (GBI), and weaker and opposite correlations with the North Atlantic Oscillation (NAO). This analysis may further help to explain melting patterns in the western GrIS from the perspective of circulation anomalies.

scholarly journals Climate of the Greenland ice sheet using a high-resolution climate model – Part 2: Near-surface climate and energy balance

2010 ◽  
Vol 4 (2) ◽  
pp. 603-639 ◽  
Author(s):  
J. Ettema ◽  
M. R. van den Broeke ◽  
E. van Meijgaard ◽  
W. J. van de Berg
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Katabatic Wind ◽  
Surface Cooling ◽  
Near Surface ◽  
Surface Climate

Abstract. The near-surface climate of the Greenland ice sheet is characterized by persistent katabatic winds and quasi-permanent temperature deficit. Using a high resolution (11 km) regional climate model allows for detailed study of the spatial variability in these phenomena and the underlying atmospheric processes. The near-surface temperature distribution over the ice sheet is clearly affected by elevation, latitude, large scale advection, meso-scale topographic features and the occurrence of summer melt. The lowest annual temperatures of −30.5 °C are found north of the highest elevations of the GrIS, whereas the lowest southern margins are warmest (−3.5 °C). Over the ice sheet, a persistent katabatic wind system develops due to radiative surface cooling and the gently slope of the surface. The strongest wind speeds are seen in the northeast where the strong large scale winds, low cloud cover and concave surface force a continuous supply of cold air, which enhances the katabatic forcing. The radiative cooling of the surface is controlled by the net longwave emission and transport of heat towards the surface by turbulence. In summer this mechanism is much weaker, leading to less horizontal variability in near-surface temperatures and wind speed.

scholarly journals Brief communication: Interest of a regional climate model against ERA5 to simulate the near-surface climate of the Greenland ice sheet

2019 ◽  
Author(s):  
Alison Delhasse ◽  
Christoph Kittel ◽  
Charles Amory ◽  
Stefan Hofer ◽  
Xavier Fettweis
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Regional Climate Models ◽  
Near Surface ◽  
Weather Forecasts ◽  
Surface Climate ◽  
Medium Range

Abstract. The ERA5 reanalysis, recently made available by the European Centre for Medium-Range Weather Forecasts (ECMWF), is a new reanalysis product at a higher resolution which will replace ERA-Interim, considered to be the best reanalysis over Greenland until now. However, so far very little is known about the performance of ERA5 when compared to ERA-Interim over the Greenland Ice Sheet (GrIS). This study shows (1) that ERA5 improves not significantly the ERA-Interim comparison with near-surface climate observations over GrIS, (2) polar regional climate models (e.g. MAR) are still a useful tool to study the GrIS climate compared to ERA5, in particular in summer, and (3) that MAR results are not sensitive to the forcing used at its lateral boundaries (ERA5 or ERA-Interim).

scholarly journals Brief communication: Evaluation of the near-surface climate in ERA5 over the Greenland Ice Sheet

2020 ◽  
Vol 14 (3) ◽  
pp. 957-965 ◽  
Author(s):  
Alison Delhasse ◽  
Christoph Kittel ◽  
Charles Amory ◽  
Stefan Hofer ◽  
Dirk van As ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Climate Models ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Regional Climate Models ◽  
The Arctic ◽  
Homogeneous Surface ◽  
Near Surface ◽  
Surface Climate

Abstract. The ERA5 reanalysis, recently made available by the European Centre for Medium-Range Weather Forecasts (ECMWF), is a new reanalysis product at a high resolution replacing ERA-Interim and is considered to provide the best climate reanalysis over Greenland to date. However, so far little is known about the performance of ERA5 over the Greenland Ice Sheet (GrIS). In this study, we compare the near-surface climate from the new ERA5 reanalysis to ERA-Interim, the Arctic System Reanalysis (ASR) as well as to a state-of-the-art polar regional climate model (MAR). The results show (1) that ERA5 does not outperform ERA-Interim significantly when compared with near-surface climate observations over GrIS, but ASR better models the near-surface temperature than both ERA reanalyses. (2) Polar regional climate models (e.g., MAR) are still a useful tool to downscale the GrIS climate compared to ERA5, as in particular the near-surface temperature in summer has a key role for representing snow and ice processes such as the surface melt. However, assimilating satellite data and using a more recent radiative scheme enable both ERA and ASR reanalyses to represent more satisfactorily than MAR the downward solar and infrared fluxes. (3) MAR near-surface climate is not affected when forced at its lateral boundaries by either ERA5 or ERA-Interim. Therefore, forcing polar regional climate models with ERA5 starting from 1950 will enable long and homogeneous surface mass balance reconstructions.

scholarly journals Long-term surface energy balance of the western Greenland Ice Sheet and the role of large-scale circulation variability

2020 ◽  
Vol 14 (11) ◽  
pp. 4181-4199
Author(s):  
Baojuan Huai ◽  
Michiel R. van den Broeke ◽  
Carleen H. Reijmer
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climate Variables ◽  
Large Scale Circulation ◽  
Near Surface ◽  
Surface Climate

Abstract. We present the surface energy balance (SEB) of the western Greenland Ice Sheet (GrIS) using an energy balance model forced with hourly observations from nine automatic weather stations (AWSs) along two transects: the Kangerlussuaq (K) transect with seven AWSs in the southwest and the Thule (T) transect with two AWSs in the northwest. Modeled and observed surface temperatures for non-melting conditions agree well with RMSEs of 1.1–1.6 K, while reasonable agreement is found between modeled and observed 10 d cumulative ice melt. Absorbed shortwave radiation (Snet) is the main energy source for melting (M), followed by the sensible heat flux (Qh). The multiyear average seasonal cycle of SEB components shows that Snet and M peak in July at all AWSs. The turbulent fluxes of sensible (Qh) and latent heat (Ql) decrease significantly with elevation, and the latter becomes negative at higher elevations, partly offsetting Qh. Average June, July and August (JJA) albedo values are <0.6 for stations below 1000 m a.s.l. and >0.7 for the higher stations. The near-surface climate variables and surface energy fluxes from reanalysis products ERA-Interim, ERA5 and the regional climate model RACMO2.3 were compared to the AWS values. The newer ERA5 product only significantly improves ERA-Interim for albedo. The regional model RACMO2.3, which has higher resolution (5.5 km) and a dedicated snow/ice module, unsurprisingly outperforms the reanalyses for (near-)surface climate variables, but the reanalyses are indispensable in detecting dependencies of west Greenland climate and melt on large-scale circulation variability. We correlate ERA5 with the AWS data to show a significant positive correlation of western GrIS summer surface temperature and melt with the Greenland Blocking Index (GBI) and weaker and opposite correlations with the North Atlantic Oscillation (NAO). This analysis may further help to explain melting patterns on the western GrIS from the perspective of circulation anomalies.

Estimating near-surface climatology of multi-reanalyses over the Greenland Ice Sheet

2021 ◽  
pp. 105676
Author(s):  
Wuying Zhang ◽  
Yetang Wang ◽  
Paul C.J.P. Smeets ◽  
Carleen H. Reijmer ◽  
Baojuan Huai ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Near Surface

scholarly journals Seasonal variability in the dynamics of marine-terminating outlet glaciers in Greenland

2010 ◽  
Vol 56 (198) ◽  
pp. 601-613 ◽  
Author(s):  
Ian M. Howat ◽  
Jason E. Box ◽  
Yushin Ahn ◽  
Adam Herrington ◽  
Ellyn M. McFadden
Keyword(s):  
Ice Sheet ◽  
Drainage System ◽  
Surface Air Temperature ◽  
Greenland Ice Sheet ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Sea Ice Concentration ◽  
Seasonal Behavior ◽  
Near Surface ◽  
Front Position

AbstractRecent studies indicate that the dynamics of fast-flowing, marine-terminating outlet glaciers of the Greenland ice sheet may be sensitive to climate and ocean forcing on sub-annual timescales. Observations of seasonal behavior of these glaciers at such high temporal resolution, however, are currently few. Here we present observations of front position, flow speed, near-surface air temperature and ocean conditions for six large marine-terminating glaciers in the Uummannaq region of West Greenland, to investigate controls on short-term glacier dynamics. As proposed by other studies, we find that seasonal front advance and retreat correlates with the formation and disappearance of an ice melange. Our data suggest that high sea-surface temperature, anomalously low sea-ice concentration and reduced melange formation in early 2003 have triggered multi-year retreat of several glaciers in the study area, which is consistent with other regions in Greenland. Of the stable glaciers, only Rink Isbræ exhibits a seasonal speed variation that correlates with variations in front position, with the others undergoing mid-summer deceleration that indicates the effects of subglacial meltwater discharge and drainage system evolution. Drainage of supraglacial lakes and water-filled crevasses results in substantial decreases in speed (40–60%) on fast-flowing glaciers. Our results demonstrate that attempts to model ice-sheet evolution must take into account short-timescale flow dynamics resulting from drainage events and oceanographic conditions.

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