Antarctic Atmospheric River Climatology and Impacts

Abstract

<p>Atmospheric rivers, broadly defined as narrow yet long bands of strong horizontal vapor transport typically imbedded in a low level jet ahead of a cold front of an extratropical cyclone, provide a sub-tropical connection to the Antarctic continent and are observed to significantly impact the affected region’s surface mass balance over short, extreme events. When an atmospheric river makes landfall on the Antarctic continent, their signature is clearly observed in increased downward longwave radiation, cloud liquid water content, surface temperature, snowfall, surface melt, and moisture transport.</p><p>Using an atmospheric river detection algorithm designed for Antarctica and regional climate simulations from MAR, we created a climatology of atmospheric river occurrence and their associated impacts on surface melt and snowfall. Despite their rarity of occurrence over Antarctica (maximum frequency of ~1.5% over a given point), they have produced significant impacts on melting and snowfall processes. From 1979-2017, atmospheric rivers landfalls and their associated radiative flux anomalies and foehn winds accounted for around 40% of the total summer surface melt on the Ross Ice Shelf (approaching 100% at higher elevations in Marie Byrd Land) and 40-80% of total winter surface melt on the ice shelves along the Antarctic Peninsula. On the other side of the continent in East Antarctica, atmospheric rivers have a greater influence on annual snowfall variability. There atmospheric rivers are responsible for 20-40% of annual snowfall with localized higher percentages across Dronning Maud Land, Amery Ice Shelf, and Wilkes Land.</p><p>Atmospheric river landfalls occur within a highly amplified polar jet pattern and often are found in the entrance region of a blocking ridge. Therefore, atmospheric river variability is connected with atmospheric blocking variability over the Southern Ocean. There has been a significant increase in atmospheric river activity over the Amundsen-Bellingshausen sea and coastline and into Dronning Maud Land region from 1980-2018. Meanwhile, there is a significant decreasing trend in the region surrounding Law Dome. Our results suggest that atmospheric rivers play a significant role in the Antarctic surface mass balance, and that any future changes in atmospheric blocking or tropical-polar teleconnections may have significant impacts on future surface mass balance projections.</p>

Synoptic Drivers of Atmospheric River Induced Precipitation Near Dronning Maud Land, Antarctica

“…MERRA-2 3 hourly single level and pressure level data are available via the Global Modeling and Assimilation Office (Global Modeling and Assimilation Office (GMAO), 2015a; Global Modeling and Assimilation Office (GMAO), 2015b). The code for the AR detection algorithm discussed in this study is publicly available (Wille, 2020). The SLP data associated with each SOM node and the dates from MERRA-2 assigned to each node and AR event is archived at the University of Colorado Boulder (Baiman, 2022)…”

Spatiotemporal variability of extreme precipitation events and associated atmospheric processes over Dronning Maud Land, East Antarctica

“…These bands frequently originate in the tropics or subtropics and then extend southward, carrying large quantities of water vapour (Ralph et al, 2004;Zhu & Newell, 1998). Due to the significant intrusions of warm moist air, ARs landfalling in coastal Antarctica contribute to heavy snowfall, accounting for about 70% to 80% of the surface mass balance (SMB) and also affect melt processes in the ice sheet (Bozkurt et al, 2018;Gorodetskaya et al, 2014;Wille et al, 2019). Wille et al (2021), in their Antarctic-wide climatological analysis of ARs from 1980-2018, showed a significant increase in the number of ARs across DML.…”

Future Atmospheric Rivers in Antarctica : intensity and impacts

“…Future variations in the snowfall are expected to follow the Clausius-Clapeyron relation, but remain largely uncertain. Currently, the SMB is driven mainly by variations in heavy precipitation events (Turner et al, 2019), in particular by Atmospheric Rivers (ARs) (Wille et al, 2021).…”

“…ARs are atmospheric water vapor transport events that are rare but contribute significantly to the exchanges between mid and high latitudes (around 90% of meridional water vapor transport is linked to ARs, (Nash et al, 2018)). Over Antarctica, they dominate the variability of snowfall (Gorodetskaya et al, 2014), but can also lead to rainfall and warm extremes through advection of warm air and increased downward longwave radiation from liquid-laden clouds (Wille et al, 2019), which will contribute negatively to the SMB.…”