Surface Mass Balance Data from Kamelryggen and Verbljud Ice Rises
Dronning Maud Land, Antarctica

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OVERVIEW
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This dataset provides spatially distributed surface mass balance (SMB) derived
from shallow-sounding radar data collected during the austral summer of 2021-22
over Kamelryggen (KAM) and Verbljud ice rises. SMB was calculated by tracking
an internal reflection horizon (IRH) in the shallow radar data and dating it
using firn cores drilled at the summits.

Goel et al., 2025 (in review for The Cryosphere)
https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2037/

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DATASET CONTENTS
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Files:
  KAM_SMB.mat (Kamelryggen - MATLAB format):  ~169,000 data points
  VER_SMB.mat (Verbljud - MATLAB format):     ~178,000 data points
  KAM_SMB.csv (Kamelryggen - CSV format)
  VER_SMB.csv (Verbljud - CSV format)

Spatially averaged SMB:
  Kamelryggen:  0.29 m ice eq. a^-1
  Verbljud:     0.46 m ice eq. a^-1

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METHODOLOGY
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Surface mass balance was derived by tracking the deepest prominent internal
reflection horizon (IRH) visible in the shallow radar data (~10 m depth at
summits) and dating it using firn cores from the ice rise summits. Firn cores
were 16.3 m deep for KAM and 14.6 m deep for VER, dated using annual layer
counting based on δ18O summer maxima and volcanic markers (non-sea salt sulphate).
The mass above the IRH was calculated using firn density profiles from the
summit cores, and SMB was obtained by dividing this mass by the IRH age. The
shallow layer approximation (Waddington et al., 2007) is applied, where vertical
strain effects on IRH depth are negligible due to the shallow depth ratio
(IRH depth / ice thickness ≈ 0.03).

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DATA FORMAT
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MATLAB FORMAT (.mat files):

Each .mat file contains a structure variable (KAM_SMB or VER_SMB) with the
following fields:

Field    Dimensions   Description
------   -----------  --------------------------------------------------------
x        N x 1        Easting (meters, EPSG:3031)
y        N x 1        Northing (meters, EPSG:3031)
z        N x 1        Surface elevation (meters above WGS84 ellipsoid)
twt      N x 1        Two-way travel time to tracked IRH (seconds)
age      scalar       Age of tracked IRH (years)
smb      N x 1        Surface mass balance (meters ice equivalent per year)

where N = number of data points along survey profiles

CSV FORMAT (.csv files):

Contains the same data with the following columns:
  x_m, y_m, z_m, twt_s, irh_age_years, smb_m_ice_eq_per_year

Note: EPSG:3031 = Polar Stereographic projection parallel to 71°S

SMB Calculation: smb = (mass above IRH) / age
where mass is calculated from twt and firn density profile

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RELATED DATASETS
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Source data:
- Shallow Radar (200 MHz) - IRH tracking
- Firn cores - Age dating and density profiles

Companion datasets:
- Ice Thickness and Bed Topography

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ACKNOWLEDGMENTS
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This work was part of the MADICE project, funded by the Ministry of Earth
Sciences (MoES), Government of India and the Research Council of Norway.
Logistical support: Maitri station and Troll station.
