Abstract. During the concluding phase of the NASA Operation
IceBridge (OIB), we successfully completed two airborne measurement
campaigns (in 2018 and 2021, respectively) using a compact S and C band radar
installed on a Single Otter aircraft and collected data over Alaskan
mountains, ice fields, and glaciers. This paper reports seasonal snow depths
derived from radar data. We found large variations in seasonal
radar-inferred depths with multi-modal distributions assuming a constant
relative permittivity for snow equal to 1.89. About 34 % of the snow
depths observed in 2018 were between 3.2 and 4.2 m, and close to 30 % of the
snow depths observed in 2021 were between 2.5 and 3.5 m. We observed snow
strata in ice facies, combined percolation and wet-snow facies, and dry-snow facies from
radar data and identified the transition areas from wet-snow facies to ice
facies for multiple glaciers based on the snow strata and radar
backscattering characteristics. Our analysis focuses on the measured strata
of multiple years at the caldera of Mount Wrangell (K'elt'aeni) to estimate the local
snow accumulation rate. We developed a method for using our radar readings
of multi-year strata to constrain the uncertain parameters of interpretation
models with the assumption that most of the snow layers detected by the
radar at the caldera are annual accumulation layers. At a 2004 ice core and
2005 temperature sensor tower site, the locally estimated average snow
accumulation rate is ∼2.89 m w.e. a−1 between the years
2003 and 2021. Our estimate of the snow accumulation rate between 2005 and
2006 is 2.82 m w.e. a−1, which matches closely to the 2.75 m w.e. a−1 inferred from independent ground-truth measurements made the same
year. The snow accumulation rate between the years 2003 and 2021 also showed
a linear increasing trend of 0.011 m w.e. a−2. This trend is
corroborated by comparisons with the surface mass balance (SMB) derived for
the same period from the regional atmospheric climate model MAR (Modèle
Atmosphérique Régional). According to MAR data, which show an
increase of 0.86 ∘C in this area for the period of 2003–2021, the
linear upward trend is associated with the increase in snowfall and rainfall
events, which may be attributed to elevated global temperatures. The
findings of this study confirmed the viability of our methodology, as well
as its underlying assumptions and interpretation models.