Evaluating a Moist Isentropic Framework for Poleward Moisture Transport: Implications for Water Isotopes Over Antarctica

Bailey, Adriana; Singh, H. A.; Nusbaumer, Jesse

doi:10.1029/2019gl082965

Cited by 22 publications

(32 citation statements)

References 52 publications

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“…Observations and modeling have also shown strongly heterogeneous spatial patterns and temporal variability in AIS SMB and its trends (e.g., Thomas et al, 2017;Lenaerts et al, 2018;Medley and Thomas, 2019), suggesting the presence of regional precipitation variability over the AIS, which has been confirmed by previous studies using reanalysis and observational data (e.g., Bromwich et al, 2011;Behrangi et al, 2016;Palerme et al, 2017). Because of the extremely low atmospheric moisture content and low local moisture flux from the ice sheet surface, the formation of precipitation over Antarctica relies on moisture transport from the surrounding oceans (e.g., Tietäväinen and Vihma, 2008).…”

Section: Introductionsupporting

confidence: 77%

Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

et al. 2020

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Abstract. We conduct sensitivity experiments using a general circulation model that has an explicit water source tagging capability forced by prescribed composites of pre-industrial sea-ice concentrations (SICs) and corresponding sea surface temperatures (SSTs) to understand the impact of sea-ice anomalies on regional evaporation, moisture transport and source–receptor relationships for Antarctic precipitation in the absence of anthropogenic forcing. Surface sensible heat fluxes, evaporation and column-integrated water vapor are larger over Southern Ocean (SO) areas with lower SICs. Changes in Antarctic precipitation and its source attribution with SICs have a strong spatial variability. Among the tagged source regions, the Southern Ocean (south of 50∘ S) contributes the most (40 %) to the Antarctic total precipitation, followed by more northerly ocean basins, most notably the South Pacific Ocean (27%), southern Indian Ocean (16 %) and South Atlantic Ocean (11 %). Comparing two experiments prescribed with high and low pre-industrial SICs, respectively, the annual mean Antarctic precipitation is about 150 Gt yr−1 (or 6 %) more in the lower SIC case than in the higher SIC case. This difference is larger than the model-simulated interannual variability in Antarctic precipitation (99 Gt yr−1). The contrast in contribution from the Southern Ocean, 102 Gt yr−1, is even more significant compared to the interannual variability of 35 Gt yr−1 in Antarctic precipitation that originates from the Southern Ocean. The horizontal transport pathways from individual vapor source regions to Antarctica are largely determined by large-scale atmospheric circulation patterns. Vapor from lower-latitude source regions takes elevated pathways to Antarctica. In contrast, vapor from the Southern Ocean moves southward within the lower troposphere to the Antarctic continent along moist isentropes that are largely shaped by local ambient conditions and coastal topography. This study also highlights the importance of atmospheric dynamics in affecting the thermodynamic impact of sea-ice anomalies associated with natural variability on Antarctic precipitation. Our analyses of the seasonal contrast in changes of basin-scale evaporation, moisture flux and precipitation suggest that the impact of SIC anomalies on regional Antarctic precipitation depends on dynamic changes that arise from SIC–SST perturbations along with internal variability. The latter appears to have a more significant effect on the moisture transport in austral winter than in summer.

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Section: Introductionsupporting

confidence: 77%

Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

et al. 2020

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“…Different phases of precipitating events over Adélie Land follow significantly different atmospheric pathways during virga and surface precipitation cases. One may also question possible differences in the origin of moisture leading to snowfall, with potential implications for ice core interpretation (Sodemann and Stohl, 2009;Bailey et al, 2019). Composite maps of moisture uptakes along the precipitating air parcels' back trajectories are presented in Fig.…”

Section: Moisture Originmentioning

confidence: 99%

Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adélie Land in Antarctica

Jullien

Vignon

Sprenger³

et al. 2020

The Cryosphere

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Abstract. Precipitation falling over the coastal regions of Antarctica often experiences low-level sublimation within the dry katabatic layer. The amount of water that reaches the ground surface is thereby considerably reduced. This paper investigates the synoptic conditions and the atmospheric transport pathways of moisture that lead to either virga – when precipitation is completely sublimated – or actual surface precipitation events over coastal Adélie Land, East Antarctica. For this purpose, the study combines ground-based lidar and radar measurements at Dumont d'Urville station (DDU), Lagrangian back trajectories, Eulerian diagnostics of extratropical cyclones and fronts, and moisture source estimations. It is found that precipitating systems at DDU are associated with warm fronts of cyclones that are located to the west of Adélie Land. Virga – corresponding to 36 % of the hours with precipitation above DDU – and surface precipitation cases are associated with the same precipitating system but they correspond to different phases of the event. Virga cases more often precede surface precipitation. They sometimes follow surface precipitation in the warm sector of the cyclone's frontal system, when the associated cyclone has moved to the east of Adélie Land and the precipitation intensity has weakened. On their way to DDU, the air parcels that ultimately precipitate above the station experience a large-scale lifting across the warm front. The lifting generally occurs earlier in time and farther from the station for virga than for precipitation. It is further shown that the water contained in the snow falling above DDU during pre-precipitation virga has an oceanic origin farther away (about 30∘ more to the west) from Adélie Land than the one contained in the snow that precipitates down to the ground surface.

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“…12,38 ). More research is necessary to identify the extent to which warming or cooling over the open Southern Ocean and sea ice zones impacts surface temperatures over high-elevation regions of the Antarctic ice sheet, as the dynamics of the extratropical atmosphere suggests that these regions should be relatively isolated from adjacent low-elevation regions 28,39,40 . Our experiments, for example, show that differences in sea ice loss and warming over the marginal ice zone are not primarily responsible for greater warming over the flattened Antarctic continent.…”

Section: Discussionmentioning

confidence: 99%

“…In the latitude-height plane, flattened Antarctic orography is associated with flattened moist isentropes over the pole, compared to present-day Antarctic orography where isentropes are more sloped (compare, for example, the 270 K moist isentrope in Fig. 5, panels a, c with those in panels b, d); this is true whether atmospheric CO 2 is at preindustrial concentrations ( In the extratropics, moist isentropes effectively act as isolines of the poleward moisture transport streamfunction 26,27 , particularly for moisture transport to the Antarctic continent 28 . The moist static energy (MSE), the sum of atmospheric latent heat, sensible heat, and geopotential, is conserved along a moist isentrope, and can be written as…”

Section: Antarctic Response To Co 2 -Doubling With Flattened Orographymentioning

confidence: 95%

Low Antarctic continental climate sensitivity due to high ice sheet orography

Singh

Polvani

2020

npj Clim Atmos Sci

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The Antarctic continent has not warmed in the last seven decades, despite a monotonic increase in the atmospheric concentration of greenhouse gases. In this paper, we investigate whether the high orography of the Antarctic ice sheet (AIS) has helped delay warming over the continent. To that end, we contrast the Antarctic climate response to CO2-doubling with present-day orography to the response with a flattened AIS. To corroborate our findings, we perform this exercise with two different climate models. We find that, with a flattened AIS, CO2-doubling induces more latent heat transport toward the Antarctic continent, greater moisture convergence over the continent and, as a result, more surface-amplified condensational heating. Greater moisture convergence over the continent is made possible by flattening of moist isentropic surfaces, which decreases humidity gradients along the trajectories on which extratropical poleward moisture transport predominantly occurs, thereby enabling more moisture to reach the pole. Furthermore, the polar meridional cell disappears when the AIS is flattened, permitting greater CO2-forced warm temperature advection toward the Antarctic continent. Our results suggest that the high elevation of the present AIS plays a significant role in decreasing the susceptibility of the Antarctic continent to CO2-forced warming.

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Evaluating a Moist Isentropic Framework for Poleward Moisture Transport: Implications for Water Isotopes Over Antarctica

Cited by 22 publications

References 52 publications

Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

Influence of sea-ice anomalies on Antarctic precipitation using source attribution in the Community Earth System Model

Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adélie Land in Antarctica

Low Antarctic continental climate sensitivity due to high ice sheet orography

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