Net Annual Mass Balance Research Articles

Little Ice Age glacier extent and temporal changes in annual mass balance (2016–2019) of Pensilungpa Glacier, Zanskar Himalaya

Glaciers and climate are known to exhibit positive feedbacks that are important for comprehending the overall glacier state. This relation is poorly understood in the relatively unexplored terrain like the Zanskar Himalaya. We have studied the impact of climate change regarding the past and present response of the Pensilungpa Glacier (PG), Zanskar Himalaya. Reconstructing the recent changes in the mass balance (2016–2019) along with the Little Ice Age (LIA) extent of the PG shows that the PG was joined by the five tributary glaciers during the LIA having an area of ~ 18 km2 and extended ~ 3 km downstream from its present-day snout located at 4470 ± 1 m.a.s.l. Since the LIA, the PG has retreated ~ 2941 ± 75 m, at an average rate of 5.6 ± 0.15 m a−1. Field observations for the last 4 years (2015–2019) show that the glacier now is retreating by ~ 27 ± 11 m at an average rate of 6.7 ± 3 m a−1, which is similar to the one since the LIA. The glaciers in the study area (Suru River valley) are mostly nourished by the Western Disturbances (during the December, January, and February) with maximum solid precipitation, and melt during the ablation period (May–October). The observed recessional trends of the PG may, therefore, be attributed to an increase in the temperature and decrease in precipitation during accumulation period. The ablation data reveal the significant influence of debris-cover on the mass balance and terminus retreat of the PG. Furthermore, the mass balance data for the last 3 years (2016–2019) show a negative trend with a small accumulation area ratio (AAR) (43%). The average net annual mass balance is estimated to be ~ − 3.67 × 106 m3 w.e. a−1 with the − 0.36 m w.e. a−1 specific balance between 2016 and 2019. During the period 2016–2019, the PG has lost ~ 11.03 × 106 m3 w.e. ice volume. The slower retreat rate and low AAR of the PG, compared to other glaciers in the area, suggest that its terrain characteristics (hypsometry, size, aspect, and slope) control the glacier dynamics and the glacier continues to adjust geometrically in response to the negative mass balance.

Comparing simple albedo scaling methods for estimating Arctic glacier mass balance

Mass balance measurements in the Canadian Arctic are limited, particularly for smaller glaciers, which introduces significant uncertainties in regional mass balance assessment. Here we report on the correlations between Moderate Resolution Imaging Spectroradiometer (MODIS) Terra albedo measurements (Version 6) and net annual mass balance for five glaciers in the Canadian Arctic over the period 2002–2016. Three glacier albedo aggregation methods are tested for the melt season (June, July and August): minimum, raw average, and interpolated average. These are evaluated in terms of a 53–71% reduction in observations due to cloud cover in the raw albedo time series. For the minimum method, the whole glacier albedo is calculated from the average of the minimum melt season albedo of each grid cell, irrespective of the day on which they occurred, resulting in R2 values between 0.20 and 0.87. In the raw average method, averaging all albedo values within a glacier outline over the melt season improves the correlation to mass balance to a range of 0.61–0.95. In the interpolated average method, linear interpolation of the raw average albedo values to fill cloud gaps, then averaging them, improves the raw average correlations for all ice masses by ~5% (R2 range 0.68–0.97). Overall, the interpolated average albedo method performs substantially better for the smallest glacier than the minimum or the raw average methods. The most negative net mass balance occurs at Grise Fiord Glacier, which is the smallest (<4.0 km2), but not the lowest elevation, glacier analysed. For this glacier, the interpolated average albedo improves the correlation with mass balance to an R2 = 0.68 (p-value < .05), compared to an R2 = 0.17 for the minimum albedo method (p-value > .05). When the five glaciers' interpolated average albedo is correlated to their ensemble mass balance, an R2 = 0.82 is achieved. These results show that interpolated MODIS Terra melt season albedo measurements can realistically approximate net annual glacier mass balance for Arctic glaciers and ice caps, without additional information about precipitation or temperature, and in the absence of a melt model.

Energy balance model of mass balance and its sensitivity to meteorological variability on Urumqi River Glacier No.1 in the Chinese Tien Shan

Energy exchanges between atmosphere and glacier surface control the net energy available for snow and ice melt. Based on the meteorological records in Urumqi River Glacier No.1 (URGN1) in the Chinese Tien Shan during the period of 2012–2015, an energy-mass balance model was run to assess the sensitivity of glacier mass balance to air temperature (T), precipitation (P), incoming shortwave radiation (Sin), relative humidity (RH), and wind speed (u) in the URGN1, respectively. The results showed that the glacier melting was mainly controlled by the net shortwave radiation. The glacier mass balance was very sensitivity to albedo for snow and the time scale determining how long the snow albedo approaches the albedo for firn after a snowfall. The net annual mass balance of URGN1 was decreased by 0.44 m w.e. when increased by 1 K in air temperature, while it was increased 0.30 m w.e. when decreased by 1 K. The net total mass balance increased by 0.55 m w.e. when increased precipitation by 10%, while it was decreased by 0.61 m w.e. when decreased precipitation by 10%. We also found that the change in glacier mass balance was non-linear when increased or decreased input condition of climate change. The sensitivity of mass balance to increase in Sin, u, and RH were at −0.015 m w.e.%−1, −0.020 m w.e.%−1, and −0.018 m w.e.%−1, respectively, while they were at 0.012 m w.e.%−1, 0.027 m w.e.%−1, and 0.017 m w.e.%−1 when decreasing in those conditions, respectively. In addition, the simulations of coupled perturbation for temperature and precipitation indicated that the precipitation needed to increase by 23% could justly compensate to the additional mass loss due to increase by 1 K in air temperature. We also found that the sensitivities of glacier mass balance in response to climate change were different in different mountain ranges, which were mainly resulted from the discrepancies in the ratio of snowfall to precipitation during the ablation season, the amount of melt energy during the ablation season, and precipitation seasonality in the different local regions.

Temperature and Melt Modeling on the Prince of Wales Ice Field, Canadian High Arctic

Abstract Near-surface temperature variability and net annual mass balance were monitored from May 2001 to April 2003 in a network of 25 sites on the Prince of Wales Ice Field, Ellesmere Island, Canada. The observational array spanned an area of 180 km by 120 km and ranged from 130 to 2010 m in altitude. Hourly, daily, and monthly average temperatures from the spatial array provide a record of mesoscale temperature variability on the ice field. The authors examine seasonal variations in the variance of monthly and daily temperature: free parameters in positive-degree-day melt models that are presently in use for modeling of glacier mass balance. An analysis of parameter space reveals that daily and seasonal temperature variability are suppressed in summer months (over a melting snow–ice surface), an effect that is important to include in melt modeling. In addition, average annual vertical gradients in near-surface temperature were −3.7°C km−1 in the 2-yr record, steepening to −4.4°C km−1 in the summer months. These gradients are less than the adiabatic lapse rates that are commonly adopted for extrapolation of sea level temperature to higher altitudes, with significant implications for modeling of snow and ice melt. Mass balance simulations for the ice field illustrate the sensitivity of melt models to different lapse rate and temperature parameterizations.

Enhanced estimation of glacier mass balance in unsampled areas by means of topographic data

AbstractA new method was developed to estimate the mass balance in unsampled areas from existing datasets. Three years of mass-balance data from two glaciers in the central Italian Alps were used to develop and test a multiple-regression method based exclusively on a 10m resolution digital terrain model. The introduction of a relative elevation attribute, which expresses the degree of wind exposure of the gridcells, notably increased the amount of explainable variance in winter balance with respect to altitude itself. The summer balance is highly correlated with elevation, but, in order to obtain reliable extrapolations, the clear-sky shortwave radiation and the diurnal cloud-cover cycle had to be taken into account. The net annual mass balance on a glacier system comprising the two monitored glaciers was calculated by applying both a single regression of winter and summer balance with altitude and the new regression method. The consistency of results was assessed against measured net balances and snow-cover maps drawn in the ablation season. The results of the new method were in close agreement with observations and proved to be less sensitive to the spatial representation of the sampled areas.

Present And Past Ice-Sheet Mass Balance Simulations For Greenland And The Tibetan Plateau

Net annual mass balance was evaluated for Greenland and the Tibetan Plateau using the meteorological forcings from the NCEP reanalysis and two GCMs (FOAM1.0 and CSM1.4) for modern climate and for different time periods extending back to the beginning of the Holocene (11,000 years ago) for the climate models. The ice-sheet budget calculations, using the degree day methodology, were performed on a finer grid than the model output by interpolating monthly precipitation and surface temperature and correcting the latter to account for the GCM’s smoothed topography. The computed net mass balance for Greenland in the present day is positive and it ranges between 290–300 mm water equivalent (w.e.)/year for the two models, values close to the NCEP estimate of 250 mm/year. The past climate simulations show that the Greenland mass balance has become slightly more positive since the beginning of the Holocene. The Tibetan Plateau’s present-day area average net mass balance is negative and ranges between –1200 and –2000 mm w.e. /year for the two models, values bracketing the NCEP estimate of 1700 mm/year, although the balance is positive over small regions of the plateau consistent with the existence of small ice caps and glaciers. The calculated past mass balance shows an increasingly less negative value for FOAM from 11,000 years ago towards the present and expansion of the positive mass balance areas, mainly due to decreased snow ablation as the summertime insolation decreases with the changes in orbital forcing; in CSM the opposite trend occurs but changes are smaller and less systematic. The result from FOAM shows that the likelihood of ice sheets developing on the Tibetan Plateau may have increased since 11000 years ago, which is consistent with some glacial records.

Mass balance and sliding velocity of the Puget lobe of the cordilleran ice sheet during the last glaciation

An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran ice sheet can be calculated from its reconstructed extent, altitude, and mass balance. Lobe dimensions and surface altitudes are inferred from ice limits and flow-direction indicators. Net annual mass balance and total ablation are calculated from relations empirically derived from modern maritime glaciers. An equilibrium-line altitude between 1200 and 1250 m is calculated for the maximum glacial advance (ca. 15,000 yr B.P.) during the Vashon Stade of the Fraser Glaciation. This estimate is in accord with geologic data and is insensitive to plausible variability in the parameters used in the reconstruction. Resultant sliding velocities are as much as 650 m/a at the equilibrium line, decreasing both up- and downglacier. Such velocities for an ice sheet of this size are consistent with nonsurging behavior. Average meltwater discharge increases monotonically downglacier to 3000 m 3/sec at the terminus and is of a comparable magnitude to ice discharge over much of the glacier's ablation area. Palcoclimatic inferences derived from this reconstruction are consistent with previous, independently derived studies of late Pleistocene temperature and precipitation in the Pacific Northwest.