Snow precipitation at four ice core sites in East Antarctica: provenance, seasonality and blocking factors

Abstract

Snow precipitation is the primary mass input to the Antarctic ice sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from ice cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the ice sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), seasonality (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low (>10 days) and high (2–6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60–70°S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies.

Appendix 1: acronyms

AAO:

Antarctic Oscillation

AN:

Antarctica Sector

ATL:

Atlantic Ocean Sector

CPT:

CircumPolar Trough

DC:

Dome C

DdU:

Dumont D’Urville

ECMWF:

European Centre Medium Range Weather Forecast

EPICA:

European Project for Ice Coring in Antarctica

ERA:

European Re-Analysis

FLEXPART:

Lagrangian Particle Dispersion Model

HYSPLIT:

Hybrid Single-Particle Lagrangian Integrated Trajectory

IND:

Indian Ocean Sector

LWD:

Law Dome

NOAA:

National Oceanic and Atmospheric Administration

PO:

Pacific Ocean Sector

PSA:

Pacific South American

RS:

Ross Sea Sector

TALDICE:

TAlos Dome Ice CorE

TDN:

Talos Dome

TLD:

Taylor Dome

VSK:

Vostok

E _u :

Eliassen-Palm flux vector

f:

Coriolis parameter

GP :

Geopotential fields

GP _ANOM :

Anomaly in GP field with respect to the long term annual mean

RH _w :

Relative Humidity with respect to water

SF:

Precipitation

T :

Temperature

u :

Zonal wind component

v :

Meridional wind component

w :

Vertical wind component

ϕ :

Latitude

σ :

Static stability

CL:

Cluster group

$CL_{IND1}^{TDN}$ :

Cluster for TJ starting from TDN and coming from high latitude over the Indian Ocean Sector

$CL_{IND2}^{TDN}$ :

Cluster for TJ starting from TDN and coming from low latitude over the Indian Ocean Sector

$CL_{ROSS}^{TDN}$ :

Cluster for TJ starting from TDN and coming from the Ross Sea Sector

$CL_{PAC}^{TDN}$ :

Cluster for TJ starting from TDN and coming from the Pacific Ocean Sector

$CL_{IND}^{DC}$ :

Cluster for TJ starting from DC and coming from the Indian Ocean Sector

$CL_{PAC}^{DC}$ :

Cluster for TJ starting from DC and coming from the Pacific Ocean Sector

$CL_{IND1}^{LWD}$ :

Cluster for TJ starting from LWD and coming from high latitude over the Indian Ocean Sector

$CL_{IND2}^{LWD}$ :

Cluster for TJ starting from LWD and coming from low latitude over the Indian Ocean Sector

$CL_{ROSS}^{TLD}$ :

Cluster for TJ starting from TLD and coming from the Ross Sea Sector

$CL_{PAC}^{TLD}$ :

Cluster for TJ starting from TLD and coming from the Pacific Ocean Sector

MPts :

Map time series

MPts ^GP :

Map time series for Geopotential field

$MPts_{{}}^{{E_{u} }}$ :

Map time series for E-P flux vector

$MPts_{{}}^{{\nabla \cdot E_{u} }}$ :

Map time series for E-P flux vector divergence

TJ:

Back Trajectory

TMR:

Blocking index as defined in Tibaldi et al. (1995)