Ice Mass Variations Research Articles

Empirical projection of global sea level in 2050 driven by Antarctic and Greenland ice mass variations

Global mean sea level rise, driven by ice mass loss in Antarctic and Greenland Ice Sheets (AIS and GrIS), is a significant consequence of global warming. Although various ice sheet models have attempted to predict the ice mass balance and subsequent sea level changes, non-trivial disagreements between models exist. In this study, we employ an empirical approach to estimate the future (2050) ice mass changes for both ice sheets, assuming their historical patterns of ice dynamics would persist in the coming decades. To achieve this, we estimate decadal-scale ice discharge variations by subtracting the surface mass balance (SMB) from the observed ice mass changes and extrapolate linear trend and acceleration components of ice discharges up to 2050. We also consider future SMB data from Coupled Model Intercomparison Project phase 6 models to estimate net ice mass balance. Our estimates suggest that from 2021 to 2050, the global sea level rise due to AIS and GrIS ranges between 6–19 mm and 15–31 mm, respectively. Additionally, we investigate regional sea level variability resulting from geoid changes induced by ice mass changes in both regions, highlighting that heterogeneous sea level changes may cause more pronounced sea level rises in lower latitude regions, where major cities are located.

Greenland Interannual Ice Mass Variations Detected by GRACE Time‐Variable Gravity

AbstractTo better understand the impact of climate forcing on Greenland ice sheet (GrIS), we study the GrIS mass variations on the interannual timescale as observed by the satellite mission of Gravity Recovery and Climate Experiment (GRACE). By employing the method of empirical orthogonal function) analysis, we find: (a) That the GrIS interannual mass variations are significantly correlated with the Pacific Decadal Oscillation, suggesting a connection to the changes of the Icelandic Low (a permanent low‐pressure system) related to PDO; (b) An East‐West Costal Dipole related to precipitation anomaly subjects to the North Atlantic Oscillation; (c) Certain contribution of the Atlantic Multidecadal Oscillation to GrIS mass variations in the form of temperature and runoff anomalies.

Antarctica ice-mass variations on interannual timescale: Coastal Dipole and propagating transports

The target is the non-secular, non-seasonal, interannual ice-mass redistribution over the Antarctica continent, as observed by the satellite mission GRACE (Gravity Recovery and Climate Experiment) for the period from 2002 to 2016. We employ the empirical orthogonal function (EOF) and complex EOF (CEOF) methods on the GRACE monthly time-variable gravity in the form of the mascon data. We find three separate phenomena on different timescales that are hitherto unreported: (i) EOF Mode 1 represents an interannual standing “seesaw” pattern largely concentrates along the coast, which we refer to as the Antarctica Coastal Dipole (ACD), with turnarounds coincident with ENSO events, relative to precipitation anomalies, whereas Mode 2-3 both correlate with the Antarctica Oscillation (AAO); (ii) the leading CEOF Mode shows two different propagating waves, one is the Eastward Propagation (EP) with the periodicity of ∼4.7 years most evident in the East Antarctica, may be induced by the Antarctica Circumpolar Wave; (iii) another is a Westward Propagation (WP) with ∼2 years periodicity in the West Antarctica that mainly travels from the Ronnie Ice Shelf to the Ross Ice Shelf, may relate to AAO.

Interannual ice mass variations over the Antarctic ice sheet from 2003 to 2017 were linked to El Niño-Southern Oscillation

Interannual variability in the ice mass balance over the Antarctic Ice Sheet (AIS) is closely related to atmospheric circulation and has large impact on estimating the secular trends of mass change. However, the spatiotemporal patterns of the interannual mass balance over the AIS have not been well characterized and their connection with atmospheric circulation remains unclear. To address this limitation, we applied a statistical method to three sets of mass balance data and extracted the interannual mass change signals over the Antarctic Peninsula (AP), the West Antarctic Ice Sheet (WAIS), the East Antarctic Ice Sheet (EAIS), and the whole AIS from 2003 to 2017. Our results reveal that the interannual mass variations over the AP and the WAIS displayed similar temporal patterns, characterized by an increase in 2003-2008, a decrease in 2009-2013, and an increase again in 2014-2016 (relative to the mean of the interannual mass variations in 2003-2017). The interannual mass variations over the EAIS showed opposite patterns, characterized by a decrease in 2003-2008, an increase in 2009-2013, and a decrease again in 2014-2016. These temporal patterns generated a maximum value and a minimum value; the peak-to-valley mass change was −14 Gt for the AP and −129 Gt for the WAIS while the valley-to-peak mass change was 149 Gt for the EAIS. The entire AIS did not exhibit similar patterns to the WAIS or the EAIS but demonstrated oscillations of about three years. We find that the interannual variation in precipitation is the reason for the interannual variation of the mass balance over the AIS and was highly correlated with El Niño-Southern Oscillation (ENSO) in 2003-2017. The interannual precipitation was positively correlated with ENSO in the AP (correlation=0.8) and the WAIS (correlation=0.9) but negatively correlated in the EAIS (correlation=-0.8). We also uncover that ENSO largely modulated the atmospheric circulation over the AIS and its surrounding regions. In 2009-2013 when ENSO was in strong negative phase, precipitation decreased in the AP and the WAIS but increased in the EAIS, conversely, in 2014-2016 when ENSO was in strong positive phase, precipitation increased in the AP and the WAIS but decreased in the EAIS. Overall, the opposite behaviors of precipitation in the WAIS and the EAIS under strong ENSO conditions explained the spatiotemporal patterns of interannual ice mass variations over the AIS in 2003-2017. The findings of the anti-correlation between the ENSO and the precipitation in the EAIS and the opposite temporal patterns between the WAIS and the EAIS are particularly novel and adds new insights to cryosphere studies.

Experimental and numerical study of insulation packages containing dry ice pellets

Shippers of healthcare and food products, in most cases, have regulatory responsibility to ensure quality by maintaining product’s temperature during transportation. Dry ice is commonly used as cold source inside the insulated cold-storage packages which are often transported via air freights. But dry ice sublimation can lead to asphyxiation of crew members or passengers due to which, several regulatory bodies have recommended safe limits of dry ice aboard aircraft mainly based on rule-of-thumb. Prior to establishing the limits, understanding dry ice sublimation is of paramount importance. Therefore the current research, experimentally and numerically explores dry ice sublimation packed in commonly encountered containers made of polystyrene foam. A three dimensional quasi-steady model is developed to predict variation of dry ice mass inside the insulation packages. The model is validated against mass and temperature measurements performed on two types of insulation packages made of different material and geometry. The model is able to fairly predict the reduction in dry ice mass over time and the end-of-sublimation time. Both experimental and numerical results show that the sublimation rate of dry ice can be reduced by covering the inner walls of insulation package with a reflective layer like aluminized mylar foil. The good agreement between model and experimental data of dry ice mass variation makes it possible for the shippers to use the modeling approach in estimating sublimation rates of dry ice.

Antarctic ice mass variations from 1979 to 2017 driven by anomalous precipitation accumulation

Antarctic ice mass balance is determined by precipitation and ice discharge, and understanding their relative contributions to contemporary Antarctic ice mass change is important to project future ice mass loss and resulting sea level rise. There has been evidence that anomalous precipitation affects Antarctic ice mass loss estimates, and thus the precipitation contribution should be understood and considered in future projections. In this study, we revisit changes in Antarctic ice mass over recent decades and examine precipitation contributions over this period. We show that accumulated (time-integrated) precipitation explains most inter-annual anomalies of Antarctic ice mass change during the GRACE period (2003–2017). From 1979 to 2017, accumulated Antarctic precipitation contributes to significant ice mass loss acceleration in the Pacific sector and deceleration in the Atlantic-Indian Sectors, forming a bi-polar spatial pattern. Principal component analysis reveals that such a bi-polar pattern is likely modulated by the Southern Annular Mode (SAM). We also find that recent ice mass loss acceleration in 2007 is related to a variation in precipitation accumulation. Overall ice discharge has accelerated at a steady rate since 1992, but has not seen a recent abrupt increase.

Improving the estimate of the secular variation of Greenland ice mass in the recent decades by incorporating a stochastic process

The irregular interannual variations observed in the Greenland ice sheet (GrIS) mass balance can be interpreted as stochastic. These variations often have large amplitudes, and, if not accounted for correctly in the mass change model parameterization, could have profound impacts on the estimate of the secular trend and acceleration. Here we propose a new mass trajectory model that includes both the conventional deterministic components and a stochastic component. This new model simultaneously estimates the secular rate and acceleration, seasonal components, and the stochastic component of mass changes. Simulations show that this new model improves estimates of model parameters, especially accelerations, over the conventional model without stochastic component. Using this new model, we estimate an acceleration of −1.6 ± 1.3 Gt/yr2 in mass change (minus means mass loss) for 2003-2017 using the Gravity Recovery and Climate Experiment (GRACE) data and an acceleration of −1.1 ± 1.3 Gt/yr2 using the modeled surface mass balance plus observed ice discharge. The corresponding rates are estimated to be −288.2 ± 12.7 Gt/yr and −274.9 ± 13.0 Gt/yr. The greatest discrepancies between the new and the conventional model parameter determinations are found in the acceleration estimates, −1.6 Gt/yr2 vs. −7.5 Gt/yr2 from the GRACE data. The estimated accelerations using the new method are apparently smaller than those estimated by other studies in terms of mass loss. Our quantitative analysis elucidates that the acceleration estimate using the conventional method is the lower bound (i.e., −7.5 Gt/yr2 for 2003–2017) while the acceleration estimated by the new method lies in the middle of the possible ranges. It is also found that these discrepancies between the new and the conventional methods diminish with sufficiently long (>20 yr) observation records.

Observational Requirements for Long-Term Monitoring of the Global Mean Sea Level and Its Components Over the Altimetry Era

Present-day global mean sea level rise is caused by ocean thermal expansion, ice mass loss from glaciers and ice sheets, as well as changes in terrestrial water storage. For that reason, sea level is one of the best indicators of climate change as it integrates the response of several components of the climate system to internal and external forcing factors. Monitoring the global mean sea level allows detecting changes (e.g., in trend or acceleration) in one or more components. Besides, assessing closure of the sea level budget allows us to check whether observed sea level change is indeed explained by the sum of changes affecting each component. If not, this would reflect errors in some of the components or missing contributions not accounted for in the budget. Since the launch of TOPEX/Poseidon in 1992, a precise 27-year continuous record of sea level change is available. It has allowed major advances in our understanding of how the Earth is responding to climate change. The last two decades are also marked by the launch of the GRACE satellite gravity mission and the development of the Argo network of profiling floats. GRACE space gravimetry allows the monitoring of mass redistributions inside the Earth system, in particular land ice mass variations as well as changes in terrestrial water storage and in ocean mass, while Argo floats allow monitoring sea water thermal expansion due to the warming of the oceans. Together, satellite altimetry, space gravity, and Argo measurements provide unprecedented insight into the magnitude, spatial variability, and causes of present-day sea level change. With this observational network, we are now in a position to address many outstanding questions that are important to planning for future sea level rise. Here, we detail the network for observing sea level and its components, underscore the importance of these observations, and emphasize the need to maintain current systems, improve their sensors, and supplement the observational network where gaps in our knowledge remain.

Detection of ice mass variation using gnss measurements at Svalbard

We compare observed uplift rates of Global Navigation Satellite Systems (gnss) with geophysical predictions at sites located on Spitsbergen. We show here that using modern postglacial rebound models, realistic mass balance for Present Day Ice Melting (pdim) and taking the deglaciation of the Little Ice Age (lia) into account, we can close the overall uplift budget at a level of a few millimetres per year. For this study we used gnss data from well-established geodetic sites in Ny-Ålesund and the new data from Hornsund. The significant increase of uplift rates since the beginning of 2011 was observed at both gnss sites. These height changes are attributed to recent increased ice mass loss of 6.0 Gt yr−1 for Svalbard. The total mass loss is estimated at 14.7 Gt yr−1. Ice unloading caused also a noticeable increase of distance between Ny-Ålesund and Hornsund. We show that the specific location of the two sites facilitates inference of differential mass loss within the Svalbard Archipelago.

Transient Variations in Glacial Mass Near Upernavik Isstrøm (West Greenland) Detected by the Combined Use of GPS and GRACE Data

AbstractThe continuously operating Global Positioning System (GPS) sites mounted on bedrock around the coast of Greenland provide important geodetic data sets to quantify the solid Earth's response to historical and present‐day ice mass variations. However, the presence of colored noise and irregular seasonal signals makes it difficult to detect transient changes in GPS time series. Here we apply the multichannel singular spectral analysis to the combination of GPS data and Gravity Recovery and Climate Experiment (GRACE) data so that we can identify and fully utilize the spatial correlations from these two independent data sets. Using the GPS and GRACE data near Upernavik Isstrøm in West Greenland as an example, we demonstrate that this method successfully detects two transient signals in ice mass variations during 2008 and 2014. Our forward modeling of loading displacements due to changes in surface mass balance (SMB) and ice dynamics suggests that the transient change starting in mid‐2008 was due to the combined contributions from dynamically induced mass loss and SMB. The transient change starting in mid‐2011 was mainly due to ablation. Specifically, the ice melted more in 2012 and less in 2013 with little contribution from anomalies in accumulation.

Fire, ice, water, and dirt: A simple climate model.

A simple paleoclimate model was developed as a modeling exercise. The model is a lumped parameter system consisting of an ocean (water), land (dirt), glacier, and sea ice (ice) and driven by the sun (fire). In comparison with other such models, its uniqueness lies in its relative simplicity yet yielding good results. For nominal values of parameters, the system is very sensitive to small changes in the parameters, yielding equilibrium, steady oscillations, and catastrophes such as freezing or boiling oceans. However, stable solutions can be found, especially naturally oscillating solutions. For nominally realistic conditions, natural periods of order 100kyrs are obtained, and chaos ensues if the Milankovitch orbital forcing is applied. An analysis of a truncated system shows that the naturally oscillating solution is a limit cycle with the characteristics of a relaxation oscillation in the two major dependent variables, the ocean temperature and the glacier ice extent. The key to getting oscillations is having the effective emissivity decreasing with temperature and, at the same time, the effective ocean albedo decreases with increasing glacier extent. Results of the original model compare favorably to the proxy data for ice mass variation, but not for temperature variation. However, modifications to the effective emissivity and albedo can be made to yield much more realistic results. The primary conclusion is that the opinion of Saltzman [Clim. Dyn. 5, 67-78 (1990)] is plausible that the external Milankovitch orbital forcing is not sufficient to explain the dominant 100kyr period in the data.

Correlated error reduction in GRACE data over Greenland using extended empirical orthogonal functions

AbstractSurface mass change estimates from Gravity Recovery and Climate Experiment (GRACE) spherical harmonic solutions are contaminated by north‐south stripe noise due largely to aliasing of high‐frequency variations into monthly samples. These meridional stripes are especially troubling for ice mass balance studies of the Greenland Ice Sheet (GrIS) where large ice mass variations are known to occur along north‐south trending coastlines. By assuming that mass variations and noise have different patterns in both space and time over Greenland, we use extended empirical orthogonal functions (EEOFs) to filter out this noise. The method is compared with a conventional approach, by examining both continent‐wide estimates and regional changes. GRACE results are compared with independent regional estimates derived from a climate model. The EEOF filter is effective at separating ice mass change signals from meridional stripe noise, with better rejection of high temporal frequency noise and less signal attenuation and spatial smoothing compared to a conventional method. We use EEOF‐filtered GRACE data to examine regional seasonal variations. Consistent with surface and other data, results show ice mass loss along the west, southwest, and east coasts during summer and gain in these regions during winter. In addition, there is summer ice mass gain in the central region of the GrIS.

Short‐term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

AbstractAs the global climate changes, understanding short‐term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak‐to‐peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS‐measured displacements for estimating seasonal and shorter‐term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half‐space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake‐based observations of loading and melting within the 1 confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice‐yearly stake measurements.

Ice and groundwater effects on long term polar motion (1979–2010)

We examine Earth’s polar motion (PM) for the years 1979–2010 to understand climate related sources of PM excitation at periods longer than a year, and to investigate Antarctic and Greenland ice mass balance contributions to long period PM. There is particular interest in years prior to the GRACE mission (prior to 2002). Although long period PM is dominantly a measure of changes in two spherical harmonic Stokes coefficients (ΔC21 and ΔS21), we remove excitations due to winds and currents by estimating them from ERA-Interim winds and GECCO2 currents. PM estimates of ΔC21 and ΔS21 are compared with model estimates of contributions from the atmosphere, oceans, water stored on the continents, and polar ice sheets. We also include contributions from groundwater depletion and mountain glaciers. PM Stokes coefficient variations agree very well with model estimates over inter-annual time scales. For ΔC21 we find good agreement at long periods, with a common long-period (quadratic) variation, but not for ΔS21. This suggests deficiencies in understanding long period ice mass variations in Antarctica and/or groundwater mass changes in Eurasia and North America.

Experiment investigation on deicing characteristics and energy efficiency using infrared ray as heat source

The adhesion and accretion of ice on ground aircraft always pose potential problem to aircraft engine operation and safety performance. Currently, chemical deicing technology is often used for aircraft deicing. However, it is effective, but not environmental-friendly, cost-effectively and always compromises material performance of aircraft. Infrared ray (IR) deicing technology, by contrast, is proved to be a promising deicing technology due to its high efficiency, safety performance and environment protection. However, the energy efficiency of IR deicing technology and physical process of ice melt have not been fully researched and understood. It is therefore necessary to study them to improve the IR deicing performances. In this paper, some important characteristics of IR deicing were firstly investigated, including ice melt rate, variation of ice temperatures and mass. Secondly, the heat transfer mechanism through whole deicing process was studied. Finally, based on the experiment results, the energy efficiency of IR deicing was calculated and discussed. And the studied results showed that the maximum energy efficiency of IR deicing could reach 53.1% at the highest setting temperature 2273 K. For melting 6.5 kg ice, the melt time was 1746 s and 1002 s at setting temperature 1073 K and 2073 K, respectively.

Uncertainty of GRACE-borne long periodic and secular ice mass variations in Antarctica

Glacial ice mass balance of Antarctica can be observed by the twin satellites of the gravity recovery and climate experiment (GRACE). The gravity fields with monthly resolution enable efficient detection of annual, long periodic and secular variations. The present study delivers an error estimation of the long-periodic and secular variations by determining the linear trend of the observed surface mass anomaly series. Among the error sources, the error of the timing of the trend fitting, the error of the glacial isostatic adjustment correction, and the error of the atmospheric correction of the GRACE monthly solutions are discussed. The investigation concludes that apart from West Antarctica, Wilkes Land, Queen Maud Land and Enderby Land no reliable trend estimates of ice mass variation can be expected, thus any results should be treated with care.

Earth rotation changes since −500 CE driven by ice mass variations

We predict the perturbation to the Earth's length-of-day (LOD) over the Common Era using a recently derived estimate of global sea-level change for this time period. We use this estimate to derive a time series of “clock error”, defined as the difference in timing of two clocks, one based on a theoretically invariant time scale (terrestrial time) and one fixed to Earth rotation (universal time), and compare this time series to millennial scale variability in clock error inferred from ancient eclipse records. Under the assumption that global sea-level change over the Common Era is driven by ice mass flux alone, we find that this flux can reconcile a significant fraction of the discrepancies between clock error computed assuming constant slowing of Earth's rotation and that inferred from eclipse records since 700 CE. In contrast, ice mass flux cannot reconcile the temporal variability prior to 700 CE.

Ice Mass Variation in Antarctica from GRACE Over 2002–2011

ABSTRACTWe detect the mass balance of the Antarctica ice sheet from GRACE for the recent period July 2002 through March 2011. Land hydrology contamination was corrected through global hydrological models and glacial isostatic adjustment (GIA) of the solid Earth since last deglaciation using the IJ05 model, and then a forward model was employed to adjust to bias due to smoothing filters and GRACE's limited resolution. The results show that there are two significant turning points for ice mass losses or gains near the early 2006 and the end of 2008. The ice mass losses in West Antarctica have accelerated dramatically during 2009–2011, while in East Antarctica the rate is positive, mainly caused by snow accumulation. Over the whole studying period, ice loss rates in West Antarctica (−108 ± 36 Gt/yr) are still significantly larger than the increase in East Antarctica (+72 ± 24) Gt/yr. Thus, the total Antarctica contribution to sea level rise is slightly negative −0.18 ± 0.02 mm/yr. The rapid change of the regional ice mass in Antarctic, in the course of only several years, suggests that the Antarctica ice sheet mass balance is more sensitive to regional climate conditions than considered before.

Accelerated ice-sheet mass loss in Antarctica from 18-year satellite laser ranging measurements

<p>Accurate estimate of the ice-sheet mass balance in Antarctic is very difficult due to complex ice sheet condition and sparse in situ measurements. In this paper, the low-degree gravity field coefficients of up to degree and order 5 derived from Satellite Laser Ranging (SLR) measurements are used to determine the ice mass variations in Antarctica for the period 1993–2011. Results show that the ice mass is losing with -36±13 Gt/y in Antarctica, -42±11 Gt/y in the West Antarctica and 6±10 Gt/y in the East Antarctica from 1993 to 2011. The ice mass variations from the SLR 5×5 have a good agreement with the GRACE 5×5, GRACE 5×5 (1&2) and GRACE (60×60) for the entire continent since 2003, but degree 5 from SLR is not sufficient to quantify ice losses in West and East Antarctica, respectively. The rate of ice loss in Antarctica is -28±17 Gt/y for 1993-2002 and -55±17 Gt/y for 2003-2011, indicating significant accelerated ice mass losses since 2003. Furthermore, the results from SLR are comparable with GRACE measurements.</p>

Sea-level responses to erosion and deposition of sediment in the Indus River basin and the Arabian Sea

Changes in sea level are of wide interest because they shape the sedimentary geologic record, modulate flood-related hazards, and reflect Earth's climate. One driver of sea-level change is the erosion and deposition of sediment, which induces changes in sea level by perturbing Earth's crust, gravity field, and rotation axis. Here we use a gravitationally self-consistent global model to explore how sediment erosion and deposition affected sea level during the most recent glacial–interglacial cycle in the northeastern Arabian Sea and the Indus River basin, where fluvial sediment fluxes are among the highest on Earth. We drive the model with a widely used reconstruction of ice mass variations over the last glacial cycle and a sediment loading history that we constructed from published erosion and deposition rate measurements. Our modeling suggests that sediment fluxes from the Indus River are large enough to produce meter-scale changes in sea level near the Indus delta in as little as a few thousand years. These sea-level perturbations are largest closest to the center of the Indus delta, and they grow larger over time as sediment deposition increases. This implies that the elevation of sea-level markers near the Indus delta will be significantly altered by sediment transfer over millennial timescales, and that such deformation should be accounted for in studies that use paleo-sea-level markers to infer past ice sheet volume or explore local processes such as sediment compaction. Our analysis highlights the role that massive fluvial sediment fluxes play in driving sea-level changes over >1000-yr timescales from the Indus River, and, by implication, from other rivers with large sediment fluxes.