scholarly journals Calibration and evaluation of a high-resolution surface mass-balance model for Paakitsoq, West Greenland

2012 ◽  
Vol 58 (212) ◽  
pp. 1047-1062 ◽  
Author(s):  
Alison F. Banwell ◽  
Ian C. Willis ◽  
Neil S. Arnold ◽  
Alexandra Messerli ◽  
Cameron J. Rye ◽  
...  
Keyword(s):  
Mass Balance ◽  
Model Performance ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Threshold Temperature ◽  
Mass Balance Model ◽  
Surface Mass ◽  
West Greenland ◽  
Landsat 7 ◽  
Normalized Difference Snow Index

AbstractModelling the hydrology of the Greenland ice sheet, including the filling and drainage of supraglacial lakes, requires melt inputs generated at high spatial and temporal resolution. Here we apply a high spatial (100 m) and temporal (1 hour) mass-balance model to a 450 km2 subset of the Paakitsoq region, West Greenland. The model is calibrated by adjusting the values for parameters of fresh snow density, threshold temperature for solid/liquid precipitation and elevation-dependent precipitation gradient to minimize the error between modelled output and surface height and albedo measurements from three Greenland Climate Network stations for the mass-balance years 2000/01 and 2004/05. Bestfit parameter values are consistent between the two years at 400 kg m-3, 2°C and +14% (100 m)-1, respectively. Model performance is evaluated, first, by comparing modelled snow and ice distribution with that derived from Landsat-7 ETM+ satellite imagery using normalized-difference snow index classification and supervised image thresholding; and second, by comparing modelled albedo with that retrieved from the MODIS sensor M0D10A1 product. Calculation of mass-balance components indicates that 6% of surface meltwater and rainwater refreezes in the snowpack and does not become runoff, such that refreezing accounts for 31% of the net accumulation.

scholarly journals A surface mass balance model for the Greenland Ice Sheet

2005 ◽  
Vol 110 (F4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Marion Bougamont ◽  
Jonathan L. Bamber ◽  
Wouter Greuell
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Mass Balance Model ◽  
Surface Mass

scholarly journals COSIPY v1.2 – An open-source coupled snowpack and ice surface energy and mass balance model

2020 ◽  
Author(s):  
Tobias Sauter ◽  
Anselm Arndt ◽  
Christoph Schneider
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Mass Balance ◽  
Surface Energy Balance ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Mass Balance Model ◽  
Physical Processes ◽  
Surface Mass ◽  
Ice Surface

Abstract. Glacial changes play a key role both from a socio-economical and political, and scientific point of view. The identification and the understanding of the nature of these changes still poses fundamental challenges for climate, glacier and water research. Many studies aim to identify the climatic drivers behind the observed glacial changes using distributed surface mass and energy balance models. Distributed surface mass balance models, which translate the meteorological conditions on glaciers into local melting rates, thus offer the possibility to attribute and detect glacier mass and volume responses to changes in the climatic forcings. A well calibrated model is a suitable test-bed for sensitivity, detection and attribution analyses for many scientific applications and often serves as a tool for quantifying the inherent uncertainties. Here we present the open-source coupled snowpack and ice surface energy and mass balance model in Python COSIPY, which provides a lean, flexible and user-friendly framework for modelling distributed snow and glacier mass changes. The model has a modular structure so that the exchange of routines or parameterizations of physical processes is possible with little effort for the user. The model has a modular structure so that the exchange of routines or parameterizations of physical processes is possible with little effort for the user. The framework consists of a computational kernel, which forms the runtime environment and takes care of the initialization, the input-output routines, the parallelization as well as the grid and data structures. This structure offers maximum flexibility without having to worry about the internal numerical flow. The adaptive sub-surface scheme allows an efficient and fast calculation of the otherwise computationally demanding fundamental equations. The surface energy-balance scheme uses established standard parameterizations for radiation as well as for the energy exchange between atmosphere and surface. The schemes are coupled by solving both surface energy balance and subsurface fluxes iteratively in such that consistent surface skin temperature is returned at the interface. COSIPY uses a one-dimensional approach limited to the vertical fluxes of energy and matter but neglects any lateral processes. Accordingly, the model can be easily set up in parallel computational environments for calculating both energy balance and climatic surface mass balance of glacier surfaces based on flexible horizontal grids and with varying temporal resolution. The model is made available on a freely accessible site and can be used for non-profit purposes. Scientists are encouraged to actively participate in the extension and improvement of the model code.

scholarly journals Surface mass balance model intercomparison for the Greenland ice sheet

2012 ◽  
Vol 6 (5) ◽  
pp. 3999-4036 ◽  
Author(s):  
C. L. Vernon ◽  
J. L. Bamber ◽  
J. E. Box ◽  
M. R. van den Broeke ◽  
X. Fettweis ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Surface Mass ◽  
Process Representation ◽  
Model Average

Abstract. Four simulations of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) are compared over the period 1960–2008. Total SMB estimates for the GrIS are in agreement within 34% of the four model average when a common ice sheet mask is used. When models' native land/ice/sea masks are used this spread increases to 57%. Variation in the spread of components of SMB from their mean: runoff 42% (29% native masks), precipitation 20% (24% native masks), melt 38% (74% native masks), refreeze 83% (142% native masks) show, with the exception of refreeze, a similar level of agreement once a common mask is used. Previously noted differences in the models' estimates are partially explained by ice sheet mask differences. Regionally there is less agreement, suggesting spatially compensating errors improve the integrated estimates. Modelled SMB estimates are compared with in situ observations from the accumulation and ablation areas. Agreement is higher in the accumulation area than the ablation area suggesting relatively high uncertainty in the estimation of ablation processes. Since the mid-1990s each model estimates a decreasing annual SMB. A similar period of decreasing SMB is also estimated for the period 1960–1972. The earlier decrease is due to reduced precipitation with runoff remaining unchanged, however, the recent decrease is associated with increased precipitation, now more than compensated for by increased melt driven runoff. Additionally, in three of the four models the equilibrium line altitude has risen since the mid-1990s, reducing the accumulation area at a rate of approximately 60 000 km2 per decade due to increased melting. Improving process representation requires further study but the use of a single accurate ice sheet mask is a logical way to reduce uncertainty among models.

scholarly journals Analysis of the Surface Mass Balance for Deglacial Climate Simulations

2020 ◽  
Author(s):  
Marie-Luise Kapsch ◽  
Uwe Mikolajewicz ◽  
Florian Andreas Ziemen ◽  
Christian B. Rodehacke ◽  
Clemens Schannwell
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Data Set ◽  
Surface Mass ◽  
Climate Conditions

Abstract. Most studies analyzing changes in the surface mass balance (SMB) of the Greenland ice sheet are limited to the last century, due to the availability of observations and the computational limitations of regional climate modeling. Using transient simulations with a comprehensive Earth System Model (ESM) we extend previous research and study changes in the SMB and equilibrium line altitude (ELA) for deglacial climate conditions. An energy balance model (EBM) is used to downscale atmospheric processes. It determines the SMB on higher spatial resolution and allows to resolve SMB variations due to topographic gradients not resolved by the ESM. An evaluation for historical climate conditions (1980–2010) shows that derived SMBs compare well with SMBs from regional modeling. Throughout the deglaciation changes in insolation dominate the Greenland SMB: 1) The increase in insolation and associated warming early in the deglaciation result in an ELA and SMB increase. The SMB increase is caused by compensating effects of melt and accumulation, as a warmer atmosphere precipitates more. After 13 ka before present (BP) melt begins to dominate and the SMB decreases. 2) The decline in insolation after 9 ka BP leads to an increasing SMB and decreasing ELA. Superimposed on these long-term changes are episodes of significant SMB/ELA decreases, related to slowdowns of the Atlantic Meridional Overturning Circulation (AMOC) that lead to cooling over most of the Northern Hemisphere. To study associated changes in the ice sheet geometry, the SMB data set is made available to the ice sheet modeling community.

scholarly journals An efficient regional energy-moisture balance model for simulation of the Greenland Ice Sheet response to climate change

2010 ◽  
Vol 4 (2) ◽  
pp. 129-144 ◽  
Author(s):  
A. Robinson ◽  
R. Calov ◽  
A. Ganopolski
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Regional Energy ◽  
Temperature And Precipitation ◽  
Moisture Balance

Abstract. In order to explore the response of the Greenland ice sheet (GIS) to climate change on long (centennial to multi-millennial) time scales, a regional energy-moisture balance model has been developed. This model simulates seasonal variations of temperature and precipitation over Greenland and explicitly accounts for elevation and albedo feedbacks. From these fields, the annual mean surface temperature and surface mass balance can be determined and used to force an ice sheet model. The melt component of the surface mass balance is computed here using both a positive degree day approach and a more physically-based alternative that includes insolation and albedo explicitly. As a validation of the climate model, we first simulated temperature and precipitation over Greenland for the prescribed, present-day topography. Our simulated climatology compares well to observations and does not differ significantly from that of a simple parameterization used in many previous simulations. Furthermore, the calculated surface mass balance using both melt schemes falls within the range of recent regional climate model results. For a prescribed, ice-free state, the differences in simulated climatology between the regional energy-moisture balance model and the simple parameterization become significant, with our model showing much stronger summer warming. When coupled to a three-dimensional ice sheet model and initialized with present-day conditions, the two melt schemes both allow realistic simulations of the present-day GIS.

scholarly journals Spatial and seasonal effects of temperature variability in a positive degree-day glacier surface mass-balance model

2013 ◽  
Vol 59 (218) ◽  
pp. 1202-1204 ◽  
Author(s):  
Julien Seguinot
Keyword(s):  
Mass Balance ◽  
Seasonal Effects ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Mass Balance Model ◽  
Glacier Surface ◽  
Surface Mass ◽  
Degree Day ◽  
Positive Degree ◽  
Effects Of Temperature

The positive degree-day model is a parameterization of surface melt widely used for its simplicity (Hock, 2003).

scholarly journals Ice-sheet contributions to future sea-level change

2006 ◽  
Vol 364 (1844) ◽  
pp. 1709-1732 ◽  
Author(s):  
J.M Gregory ◽  
P Huybrechts
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
General Circulation ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
General Circulation Models ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Global Average

Accurate simulation of ice-sheet surface mass balance requires higher spatial resolution than is afforded by typical atmosphere–ocean general circulation models (AOGCMs), owing, in particular, to the need to resolve the narrow and steep margins where the majority of precipitation and ablation occurs. We have developed a method for calculating mass-balance changes by combining ice-sheet average time-series from AOGCM projections for future centuries, both with information from high-resolution climate models run for short periods and with a 20 km ice-sheet mass-balance model. Antarctica contributes negatively to sea level on account of increased accumulation, while Greenland contributes positively because ablation increases more rapidly. The uncertainty in the results is about 20% for Antarctica and 35% for Greenland. Changes in ice-sheet topography and dynamics are not included, but we discuss their possible effects. For an annual- and area-average warming exceeding in Greenland and in the global average, the net surface mass balance of the Greenland ice sheet becomes negative, in which case it is likely that the ice sheet would eventually be eliminated, raising global-average sea level by 7 m.

scholarly journals Surface mass balance, thinning and iceberg production, Columbia Glacier, Alaska, 1948–2007

2011 ◽  
Vol 57 (203) ◽  
pp. 431-440 ◽  
Author(s):  
L.A. Rasmussen ◽  
H. Conway ◽  
R.M. Krimmel ◽  
R. Hock
Keyword(s):  
Mass Balance ◽  
Meteorological Data ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Mass Balance Model ◽  
Surface Mass ◽  
Surface Ablation ◽  
Positive Balance ◽  
Remarkable Result ◽  
The Difference

AbstractA mass-balance model using upper-air meteorological data for input was calibrated with surface mass balance measured mainly during 1977–78 at 67 sites on Columbia Glacier, Alaska, between 135 and 2645 m a.s.l. Root-mean-square error, model vs measured, is 1.0 m w.e. a−1, with r2 = 0.88. A remarkable result of the analysis was that both precipitation and the factor in the positive degree-day model used to estimate surface ablation were constant with altitude. The model was applied to reconstruct glacier-wide components of surface mass balance over 1948–2007. Surface ablation, 4 km3 ice eq. a−1 (ice equivalent), has changed little throughout the period. From 1948 until about 1981, when drastic retreat began, the surface mass balance was positive but changes in glacier geometry were small, so the positive balance was offset by calving, ∼0.9 km3 ice eq. a−1 . During retreat, volume loss of the glacier accounted for 92% of the iceberg production. Calving increased to ∼4.3 km3 ice eq. a−1 from 1982 to 1995, and after that until 2007 to ∼8.0 km3 ice eq. a−1, which was about twice the loss by surface ablation, whereas prior to retreat it was only about a quarter as much. Calving is calculated as the difference between glacier-wide surface mass balance and geodetically determined volume change.

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