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

Journal Article · 04 February 2020 · The Cryosphere (Online)

DOI: https://doi.org/10.5194/tc-14-429-2020 · OSTI ID:1597125

Wang, Hailong  ^[1]; Fyke, Jeremy G.  ^[2]; Lenaerts, Jan  ^[3]; Nusbaumer, Jesse M. ^[4]; Singh, Hansi AK ^[1]; Noone, David C. ^[5]; Rasch, Philip J. ^[1]; Zhang, Rudong ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Univ. of Utrecht (Netherlands)
4. Univ. of Colorado, Boulder, CO (United States)
5. Oregon State Univ., Corvallis, OR (United States)

Abstract. We conduct sensitivity experiments using a general circulation model thathas an explicit water source tagging capability forced by prescribedcomposites of pre-industrial sea-ice concentrations (SICs) and correspondingsea surface temperatures (SSTs) to understand the impact of sea-ice anomalies on regional evaporation, moisture transport and source–receptorrelationships for Antarctic precipitation in the absence of anthropogenicforcing. Surface sensible heat fluxes, evaporation and column-integratedwater vapor are larger over Southern Ocean (SO) areas with lower SICs. Changes inAntarctic precipitation and its source attribution with SICs have a strongspatial variability. Among the tagged source regions, the Southern Ocean(south of 50°S) contributes the most (40 %) to the Antarctictotal precipitation, followed by more northerly ocean basins, most notablythe South Pacific Ocean (27%), southern Indian Ocean (16 %) and SouthAtlantic Ocean (11 %). Comparing two experiments prescribed with high andlow pre-industrial SICs, respectively, the annual mean Antarcticprecipitation is about 150 Gt yr- 1 (or 6 %) more in the lower SICcase than in the higher SIC case. This difference is larger than themodel-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 interannualvariability of 35 Gt yr-1 in Antarctic precipitation that originatesfrom the Southern Ocean. The horizontal transport pathways from individualvapor source regions to Antarctica are largely determined by large-scaleatmospheric circulation patterns. Vapor from lower-latitude source regionstakes elevated pathways to Antarctica. In contrast, vapor from the SouthernOcean moves southward within the lower troposphere to the Antarcticcontinent along moist isentropes that are largely shaped by local ambientconditions 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–SSTperturbations along with internal variability. The latter appears to have a more significant effect on the moisture transport in austral winter than in summer.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830; AC05-76RLO1830
• OSTI ID: 1597125
• Alternate ID(s): OSTI ID: 1605001
• Report Number(s): PNNL-SA-147435
• Journal Information: The Cryosphere (Online), Vol. 14, Issue 2; ISSN 1994-0424
• Publisher: European Geosciences UnionCopyright Statement
• Country of Publication: United States
• Language: English