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

Abstract

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 moremore » 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.« less

Authors:

Wang, Hailong; Fyke, Jeremy G. ;

• Search DOE PAGES for author "Fyke, Jeremy G."
• Search DOE PAGES for ORCID "0000-0002-4522-3019"

Lenaerts, Jan T. M. ;

• Search DOE PAGES for author "Lenaerts, Jan T. M."
• Search DOE PAGES for ORCID "0000-0003-4309-4011"

Nusbaumer, Jesse M.; Singh, Hansi; Noone, David; Rasch, Philip J.; Zhang, Rudong

Publication Date:

Tue Feb 04 00:00:00 EST 2020

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1597125

Alternate Identifier(s):

OSTI ID: 1605001

Report Number(s):

PNNL-SA-147435
Journal ID: ISSN 1994-0424

Grant/Contract Number:  

AC05-76RLO1830; AC05-76RL01830

Resource Type:

Published Article

Journal Name:

The Cryosphere (Online)

Additional Journal Information:

Journal Name: The Cryosphere (Online) Journal Volume: 14 Journal Issue: 2; Journal ID: ISSN 1994-0424

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Antarctic sea ice; Preciptiation; Water vapor; source attribution; atmospheric circulation