scholarly journals Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modeling

2020 ◽  
Vol 14 (10) ◽  
pp. 3367-3380
Author(s):  
Thore Kausch ◽  
Stef Lhermitte ◽  
Jan T. M. Lenaerts ◽  
Nander Wever ◽  
Mana Inoue ◽  
...  
Keyword(s):  
Mass Balance ◽  
Wind Erosion ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Windward Side ◽  
Leeward Side ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Local Erosion

Abstract. About 20 % of all snow accumulation in Antarctica occurs on the ice shelves. There, ice rises control the spatial surface mass balance (SMB) distribution by inducing snowfall variability and wind erosion due to their topography. Moreover these ice rises buttress the ice flow and represent ideal drilling locations for ice cores. In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO2 and the implications of this SMB variability for ice rises as an ice core drilling site. By combining ground-penetrating radar (GPR) profiles from two ice rises in Dronning Maud Land with ice core dating, we reconstruct spatial and temporal SMB variations from 1983 to 2018 and compare the observed SMB with output from RACMO2 and SnowModel. Our results show snowfall-driven differences of up to 1.5 times higher SMB on the windward side of both ice rises than on the leeward side as well as a local erosion-driven minimum at the ice divide of the ice rises. RACMO2 captures the snowfall-driven differences but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO2 forcing. Observed temporal variability of the average SMBs, retrieved from the GPR data for four time intervals in the 1983–2018 range, are low at the peak of the easternmost ice rise (∼0.06 mw.e.yr-1), while they are higher (∼0.09 mw.e.yr-1) on the windward side of the ice rise. This implies that at the peak of the ice rise, higher snowfall, driven by orographic uplift, is balanced out by local erosion. As a consequence of this, the SMB recovered from the ice core matches the SMB from the GPR at the peak of the ice rise but not at the windward side of the ice rise, suggesting that the SMB signal is damped in the ice core.

Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modelling

2020 ◽  
Author(s):  
Thore Kausch ◽  
Stef Lhermitte ◽  
Jan T.M. Lenaerts ◽  
Nander Wever ◽  
Mana Inoue ◽  
...  
Keyword(s):  
Mass Balance ◽  
Wind Erosion ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Windward Side ◽  
Leeward Side ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Local Erosion

<p>About 20% of all snow accumulation in Antarctica occurs on the ice shelfs and ice rises, locations within the ice shelf where the ice is locally grounded on topography. These ice rises largely control the spatial surface mass balance (SMB) distribution by inducing snowfall variability due to orographic uplift and by inducing wind erosion due altering the wind conditions. Moreover these ice rises buttress the ice flow and represent an ideal drilling locations for ice cores.</p><p>In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO, and the implications of this SMB variability for ice rises as an ice core drilling side. By combining ground penetrating radar profiles from two ice rises in Dronning Maud Land with ice core dating we reconstruct spatial and temporal SMB variations across both ice rises from 1982 to 2017. Subsequently, the observed SMB is compared with output from RACMO, SnowModel to quantify the contribution of the different processes that control the spatial SMB variability across the ice rises. Finally, the observed SMB is compared with Sentinel-1 backscatter data to extrapolate spatial SMB trends over larger areas.</p><p>Our results show snowfall-driven differences of up to ~ 0.24 m w.e./yr between the windward and the leeward side of both ice rises as well as a local erosion driven minimum at the peak of the ice rises. RACMO captures the snowfall-driven differences, but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO forcing. Observed temporal variability of the average SMBs calculated for 4 time intervals in the 1982-2017 range are low at the peak of the easternmost ice rise (~ 0.03 m w.e./yr), while being three times higher (~ 0.1 m w.e./yr) on the windward side of the ice rise. This implicates that at the peak of the ice rise, higher snowfall, driven by regional processes, such as orographic uplift, is balanced out by local erosion.  Comparison of the observed SMB gradients with Sentinel-1 data finally shows the potential of SAR satellite observations to represent spatial variability in SMB across ice shelves and ice rises.</p>

scholarly journals Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modeling

2020 ◽  
Author(s):  
Thore Kausch ◽  
Stef Lhermitte ◽  
Jan T. M. Lenaerts ◽  
Nander Wever ◽  
Mana Inoue ◽  
...  
Keyword(s):  
Mass Balance ◽  
Wind Erosion ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Windward Side ◽  
Leeward Side ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Local Erosion

Abstract. About 20 % of all snow accumulation in Antarctica occurs on the ice shelves. There, ice rises control the spatial surface mass balance (SMB) distribution by inducing snowfall variability and wind erosion due to their topography. Moreover these ice rises buttress the ice flow and represent ideal drilling locations for ice cores. In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO2, and the implications of this SMB variability for ice rises as an ice core drilling site. By combining ground penetrating radar (GPR) profiles from two ice rises in Dronning Maud Land with ice core dating we reconstruct spatial and temporal SMB variations from 1982 to 2017 and compare the observed SMB with output from RACMO2 and SnowModel. Our results show snowfall driven differences of up to 1.5 times higher SMB on the windward side of both ice rises than on the leeward side, as well as a local erosion driven minimum at the ice divide of the ice rises. RACMO2 captures the snowfall driven differences, but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO2 forcing. Observed temporal variability of the average SMBs, retrieved from the GPR data for four time intervals in the 1982–2017 range, are low at the peak of the easternmost ice rise (~ 0.03 m w.e./yr), while being three times higher (~ 0.1 m w.e./yr) on the windward side of the ice rise. This implies that at the peak of the ice rise, higher snowfall, driven by orographic uplift, is balanced out by local erosion. As a consequence of this the SMB recovered from the ice core matches the SMB from the GPR at the peak of the ice rise, but not at the windward side of the ice rise, suggesting that the SMB signal is dampened in the ice core.

scholarly journals Climate dependent contrast in surface mass balance in East Antarctica over the past 216 ka

2016 ◽  
Vol 62 (236) ◽  
pp. 1037-1048 ◽  
Author(s):  
F. PARRENIN ◽  
S. FUJITA ◽  
A. ABE-OUCHI ◽  
K. KAWAMURA ◽  
V. MASSON-DELMOTTE ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Ice Cores ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Last Interglacial ◽  
Surface Mass ◽  
The Past ◽  
Water Stable Isotope ◽  
Global Mean Sea Level

ABSTRACTDocumenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice-sheet contribution to global mean sea-level change. Here we reconstruct past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 a, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. Our results therefore reveal larger amplitudes of changes in SMB at EDC compared with DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared with DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 0.2 from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends.

scholarly journals Temporal and spatial variability of surface mass balance at Dome Fuji, East Antarctica, by the stake method from 1995 to 2006

2008 ◽  
Vol 54 (184) ◽  
pp. 107-116 ◽  
Author(s):  
Takao Kameda ◽  
Hideaki Motoyama ◽  
Shuji Fujita ◽  
Shuhei Takahashi
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Frequency Distributions ◽  
Temporal And Spatial Variability ◽  
The Antarctic ◽  
Height Data

AbstractThe surface mass balance (SMB) at Dome Fuji, East Antarctica, was estimated using 36 bamboo stakes (grid of 6 × 6, placed at 20 m intervals) from 1995 to 2006. The heights of the stake tops from the snow surface were measured at 0.5 cm resolution twice monthly in 1995, 1996, 1997 and 2003, and once a year for the rest of the study period. To account for snow settling, the average snow density at the stake base during the measurements was used for converting the stake-height data to SMB. The annual SMB from 1995 to 2006 at Dome Fuji was 27.3 ± 1.5 kg m−2 a−1. This result agrees well with the annual SMB from AD 1260 to 1993 (26.4 kg m−2 a−1) estimated from volcanic signals in the Dome Fuji ice core. Over the period 1995–2006, there were 37 (8.6% of the measurements) negative or zero annual SMB results. Variation in the multi-year averages of annual SMB decreased with the square root of the number of observation years, and 10 years of observations of a single stake allowed the estimation of annual SMB at ±10% accuracy. The frequency distributions of annual and monthly SMB were examined. The findings clarify the complex behavior of the annual and monthly SMB at Dome Fuji, which will be common phenomena in areas of low snow accumulation of the interior of the Antarctic ice sheet.

scholarly journals Reconciling the surface temperature–surface mass balance relationship in models and ice cores in Antarctica over the last two centuries

2020 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jan T. M. Lenaerts ◽  
Elizabeth R. Thomas
Keyword(s):  
Mass Balance ◽  
Large Scale ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Weak Correlation ◽  
Surface Mass ◽  
The Past ◽  
Ice Core Records

Abstract. Ice cores are an important record of the past surface mass balance (SMB) of ice sheets, with SMB mitigating the ice sheets’ sea level impact over the recent decades. For the Antarctic Ice Sheet (AIS), SMB is dominated by large-scale atmospheric circulation, which collects warm moist air from further north and releases it in the form of snow as widespread accumulation or focused atmospheric rivers on the continent. This implies that the snow deposited at the surface of the AIS should record strongly coupled SMB and surface air temperature (SAT) variations. Ice cores use δ18O as a proxy for SAT as they do not record SAT directly. Here, using isotope-enabled global climate models and the RACMO2.3 regional climate model, we calculate positive SMB-SAT and δ18O-SMB correlations over ∼90 % of the AIS. The high spatial resolution of the RACMO2.3 model allows us to highlight a number of areas where SMB and SAT are not correlated, and show that wind-driven processes acting locally, such as Foehn and katabatic effects, can overwhelm the large-scale atmospheric input in SMB and SAT responsible for the positive SMB-SAT correlations. We focus in particular on Dronning Maud Land, East Antarctica, where the ice promontories clearly show these wind-induced effects. However, using the PAGES2k ice core compilations of SMB and δ18O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak correlation, on the order of 0.1, between SMB and δ18O over the past ~150 years. We obtain an equivalently weak correlation between ice core SMB and the SAT reconstruction of Nicolas and Bromwich (2014) over the past ~50 years, although the ice core sites are not spatially co-located with the areas displaying a low SMB-SAT correlation in the models. To resolve the discrepancy between the measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB-SAT correlation. This increase shows that the weak measured correlation likely results from random noise present in the ice core records, but is not large enough to match the correlation calculated in the models. Our results indicate thus a positive correlation between SAT and SMB in models and ice core reconstructions but with a weaker value in observations that may be due to missing processes in models or some systematic biases in ice core data that are not removed by a simple average.

scholarly journals Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr

2015 ◽  
Vol 11 (1) ◽  
pp. 377-405 ◽  
Author(s):  
F. Parrenin ◽  
S. Fujita ◽  
A. Abe-Ouchi ◽  
K. Kawamura ◽  
V. Masson-Delmotte ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Ice Sheet ◽  
Ice Cores ◽  
Atmospheric Modeling ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Last Interglacial ◽  
Surface Mass ◽  
The Past

Abstract. Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 years, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, decreasing during cold periods and increasing during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within interglacial periods and during the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 30% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not closely related to isotopic changes are one of the possible causes of the observed gaps between the ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for ice sheet modeling (for which SMB is a boundary condition) or atmospheric modeling (our inferred SMB ratio could serve as a test).

scholarly journals Annual Greenland accumulation rates (2009–2012) from airborne snow radar

2016 ◽  
Vol 10 (4) ◽  
pp. 1739-1752 ◽  
Author(s):  
Lora S. Koenig ◽  
Alvaro Ivanoff ◽  
Patrick M. Alexander ◽  
Joseph A. MacGregor ◽  
Xavier Fettweis ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Ultra Wideband ◽  
The Arctic ◽  
Surface Mass Balance ◽  
Accumulation Rates ◽  
Surface Mass

Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2–6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009–2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

Examining the strength of the link between surface temperature and surface mass balance in ice cores and models over the last centuries in Antarctica

2020 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jan T.M. Lenaerts ◽  
Elizabeth R. Thomas
Keyword(s):  
Large Scale ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Regional Model ◽  
Snow Accumulation ◽  
Surface Mass Balance ◽  
Weak Correlation ◽  
Surface Mass ◽  
The Past

<p>Ice cores constitute an important record of the past surface mass balance (SMB) of the ice sheets, with SMB ultimately modulating the ice sheets’ sea level impact. For the Antarctic Ice Sheet (AIS), SMB is dominated by snow accumulation and strongly controlled by atmospheric circulation. Large-scale atmospheric depressions collect warmth and moisture from further north that they then release over the AIS in the form of widespread accumulation or focused atmospheric rivers. This implies that snow deposited at the surface of the AIS should show strongly coupled SMB and surface air temperatures (SAT) variations. Ice cores do not record SAT directly but their d<sup>18</sup>O record is often used as a temperature proxy.</p><p> </p><p>Here, using the PAGES 2k Network ice core compilations of SMB and d<sup>18</sup>O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak correlation between SMB and d<sup>18</sup>O over historical timescales, and an equivalently weak correlation between SMB and SAT based on the Nicolas & Bromwich (2014) SAT reconstructions. However, we calculate a strong and positive SMB-SAT correlation in the majority of regions of the AIS using Global Climate Models (GCM) and the regional model RACMO2.3p2.</p><p> </p><p>To resolve the discrepancy between measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB-SAT correlation. This increase in measured SMB-SAT correlation likely results from noise present in the ice core records, but is not enough to match the strong correlation calculated in the models. On the model side, the high spatial resolution of the RACMO2.3p2 model allows us to highlight a number of areas of the AIS where SMB and SAT are not strongly correlated. We describe how wind-driven processes acting on the SMB and SAT locally, through Foehn and katabatic effects, can overwhelm the large-scale atmospheric input that induces the positive SMB-SAT correlations. In particular, we focus on Dronning Maud Land, East Antarctica, where each ice promontory clearly shows this wind-driven snow redistribution. Nevertheless, those regions displaying a low SMB-SAT correlation cover only a small fraction of the AIS and are not sufficient to explain the model-data discrepancy, suggesting a critical role of processes at a scale smaller than the one resolved by the regional model.</p><p> </p><p>References:</p><p>Thomas, E. R., 2017, Regional Antarctic snow accumulation over the past 1000 years, Climate of the Past, 13, 1491–1513.</p><p>Stenni, B. et al., 2017, Antarctic climate variability on regional and continental scales over the last 2000 years, Climate of the Past, 13, 1609–1634.</p><p>Nicolas, J. P. & Bromwich, D. H., 2014, New reconstruction of Antarctic near-surface temperatures: Multidecadal trends and reliability of global reanalyses, Journal of Climate, 27, 8070–8093.</p>

scholarly journals Annual-layer determinations and 167 year records of past climate of H72 ice core in east Dronning Maud Land, Antarctica

2002 ◽  
Vol 35 ◽  
pp. 471-479 ◽  
Author(s):  
Fumihiko Nishio ◽  
Teruo Furukawa ◽  
Gen Hashida ◽  
Makoto Igarashi ◽  
Takao Kameda ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Tritium Content ◽  
Surface Mass ◽  
Annual Layer ◽  
Dronning Maud Land ◽  
Annual Resolution ◽  
Continuous Accumulation

AbstractTo determine annual layers for reconstructing the past environment at annual resolution from ice cores, we employed snow-stake data back to 1972, tritium content, solid electrical conductivity measurements (ECM) and stratigraphic properties for the 73m ice core at the H72 site, east Dronning Maud Land, Antarctica. the average annual surface mass balance at H72 is 307 mma–1w.e. during the last 27 years from continuous accumulation data, 317 mma–1 w.e. according to the densification model and 311 mma–1 w.e. according to the average surface mass balance for 167 years based on annual-layer counting. the ECM age is closely coincident with tritium age, and corresponds with the snow-stake record back to AD 1972 from the surface to 15 m depth. the H72 ice core is dated as AD 1831by ECMat 73.16 mdepth.The time series of yearly surface mass balance at H72 shows an almost constant 311 mm a–1 w.e. for the last 167 years. the oxygen-isotope records indicate a significant trend to lower values, with negative gradient of 1.7% (100 years)–1.

scholarly journals Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica

2016 ◽  
Vol 10 (5) ◽  
pp. 2501-2516 ◽  
Author(s):  
Morgane Philippe ◽  
Jean-Louis Tison ◽  
Karen Fjøsne ◽  
Bryn Hubbard ◽  
Helle A. Kjær ◽  
...  
Keyword(s):  
Mass Balance ◽  
20Th Century ◽  
Source Region ◽  
Ice Core ◽  
Ice Cores ◽  
First Record ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Dronning Maud Land

Abstract. Ice cores provide temporal records of surface mass balance (SMB). Coastal areas of Antarctica have relatively high and variable SMB, but are under-represented in records spanning more than 100 years. Here we present SMB reconstruction from a 120 m-long ice core drilled in 2012 on the Derwael Ice Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotope (δ18O and δD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the ice core is dated to AD 1759 ± 16, providing a climate proxy for the past  ∼ 250 years. The core's annual layer thickness history is combined with its gravimetric density profile to reconstruct the site's SMB history, corrected for the influence of ice deformation. The mean SMB for the core's entire history is 0.47 ± 0.02 m water equivalent (w.e.) a−1. The time series of reconstructed annual SMB shows high variability, but a general increase beginning in the 20th century. This increase is particularly marked during the last 50 years (1962–2011), which yields mean SMB of 0.61 ± 0.01 m w.e. a−1. This trend is compared with other reported SMB data in Antarctica, generally showing a high spatial variability. Output of the fully coupled Community Earth System Model (CESM) suggests that, although atmospheric circulation is the main factor influencing SMB, variability in sea surface temperatures and sea ice cover in the precipitation source region also explain part of the variability in SMB. Local snow redistribution can also influence interannual variability but is unlikely to influence long-term trends significantly. This is the first record from a coastal ice core in East Antarctica to show an increase in SMB beginning in the early 20th century and particularly marked during the last 50 years.

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