Assessing Present-Day Atmospheric Control Over the Surface Mass Balance
of Patagonian Icefields Through Modeling
Abstract
The Patagonian Icefields (Northern Patagonia Icefield and Southern
Patagonia Icefield) are the largest ice bodies in the Southern
Hemisphere outside Antarctica. Nonetheless, little is known about their
main meteorological and glaciological features (mean state, variability
and trends) in present climate (last ~30 years). The
lack of temporarily and spatially dense observational data in this area
has imposed a limitation on the assessment of the atmosphere-cryosphere
interaction, a key issue for understanding the past, present and future
evolution of these ice bodies and more generally, the southern Andes
cryosphere. In this work, we overcome the absence of surface data by
modeling the present-day atmospheric surface conditions for southern
Andes. We first use a regional climate model (RegCMv4) to dynamically
downscale the ERA-Interim reanalysis at 10-km spatial resolution for the
period 1980-2015. Then, we statistically downscale its outputs to a
450-m resolution grid. This meteorological forcing is used later as an
input for a simplified surface mass balance model. The surface mass
balance output is analyzed particularly for spatial and temporal
variability as well as trends. This allows us to have a better
understanding of the local-scale atmospheric control (i.e., surface
temperature, solar radiation and precipitation) over the surface mass
balance of Patagonian Icefields. In order to assess the large-scale
control over the surface mass balance of Patagonian Icefields, time
series of spatially-averaged modeled fields are projected upon main
atmospheric fields obtained from ERA-Interim reanalysis. Main results
show that years of relatively high (low) surface mass balance are
associated with low (high) pressure anomalies near the Bellingshausen
Sea, causing an anomalous cyclonic (anticyclonic) circulation that
enhances (reduces) the westerlies impinging the Patagonian Icefields
which in turn increments (decrements) the surface mass balance. Only
weak correlations between the mass balance and the main atmospheric
modes of variability (ENSO, PDO, SAM) were found, suggesting little
dependency between these modes and the surface mass balance of the
Patagonian Icefields.