[1] Previous studies have shown strong contrasting trends in annual sea ice duration and in monthly sea ice concentration in two regions of the Southern Ocean: decreases in the western Antarctic Peninsula/southern Bellingshausen Sea (wAP/sBS) region and increases in the western Ross Sea (wRS) region. To better understand the evolution of these regional sea ice trends, we utilize the full temporal (quasi-daily) resolution of satellite-derived sea ice data to track spatially the annual ice edge advance and retreat from 1979 to 2004. These newly analyzed data reveal that sea ice is retreating 31 ± 10 days earlier and advancing 54 ± 9 days later in the wAP/sBS region (i.e., total change over , whereas in the wRS region, sea ice is retreating 29 ± 6 days later and advancing 31 ± 6 days earlier. Changes in the wAP/sBS and wRS regions, particularly as observed during sea ice advance, occurred in association with decadal changes in the mean state of the Southern Annular Mode (SAM; negative in the 1980s and positive in the 1990s) and the high-latitude response to El Niño-Southern Oscillation (ENSO). In general, the high-latitude ice-atmosphere response to ENSO was strongest when -SAM was coincident with El Niño and when +SAM was coincident with La Niña, particularly in the wAP/sBS region. In total, there were 7 of 11 -SAMs between 1980 and 1990 and the 7 of 10 +SAMs between 1991 and 2000 that were associated with consistent decadal sea ice changes in the wAP/sBS and wRS regions, respectively. Elsewhere, ENSO/SAMrelated sea ice changes were not as consistent over time (e.g., western Weddell, Amundsen, and eastern Ross Sea region), or variability in general was high (e.g., central/ eastern Weddell and along East Antarctica).

Many remote and local climate variabilities influence Antarctic sea ice at different time scales. The strongest sea ice teleconnection at the interannual time scale was found between El Niño–Southern Oscillation (ENSO) events and a high latitude climate mode named the Antarctic Dipole. The Antarctic Dipole is characterized by an out-of-phase relationship between sea ice and surface temperature anomalies in the South Pacific and South Atlantic, manifesting itself and persisting 3–4 seasons after being triggered by the ENSO forcing. This study examines the life cycles of ENSO warm and cold events in the tropics and associated evolution of the ADP in high latitudes of the Southern Hemisphere. In evaluating the mechanisms that form the ADP, the study suggests a synthesized scheme that links these high latitude processes with ENSO teleconnection in both the Pacific and Atlantic basins. The synthesized scheme suggests that the two main mechanisms responsible for the formation/maintenance of the Antarctic Dipole are the heat flux due to the mean meridional circulation of the regional Ferrel Cell and regional anomalous circulation generated by stationary eddies. The changes in the Hadley Cell, the jet stream in the subtropics, and the Rossby Wave train associated with ENSO link the tropical forcing to these high latitude processes. Moreover, these two mechanisms operate in phase and are comparable in magnitude. The positive feedback between the jet stream and stationary eddies in the atmosphere, the positive feedback within the air-sea-ice system, and the seasonality all reinforce the anomalies, resulting in persistent Antarctic Dipole anomalies.

This study statistically evaluates the relationship between Antarctic sea ice extent and global climate variability. Temporal cross correlations between detrended Antarctic sea ice edge (SIE) anomaly and various climate indices are calculated. For the sea surface temperature (SST) in the eastern equatorial Pacific and tropical Indian Ocean, as well as the tropical Pacific precipitation, a coherent propagating pattern is clearly evident in all correlations with the spatially averaged (over 12Њ longitude) detrended SIE anomalies (͗SIE*͘). Correlations with ENSO indices imply that up to 34% of the variance in ͗SIE*͘ is linearly related to ENSO. The ͗SIE*͘ has even higher correlations with the tropical Pacific precipitation and SST in the tropical Indian Ocean. In addition, correlation of ͗SIE*͘ with global surface temperature produces four characteristic correlation patterns: 1) an ENSO-like pattern in the Tropics with strong correlations in the Indian Ocean and North America (r Ͼ 0.6); 2) a teleconnection pattern between the eastern Pacific region of the Antarctic and western-central tropical Pacific; 3) an Antarctic dipole across the Drake Passage; and 4) meridional banding structures in the central Pacific and Atlantic expending from polar regions to the Tropics, even to the Northern Hemisphere. The SIE anomalies in the Amundsen Sea, Bellingshausen Sea, and Weddell Gyre of the Antarctic polar ocean sectors show the strongest polar links to extrapolar climate. Linear correlations between ͗SIE*͘ in those regions and global climate parameters pass a local significance test at the 95% confidence level. The field significance, designed to account for spatial coherence in the surface temperature, is evaluated using quasiperiodic colored noise that is more appropriate than white noise. The fraction of the globe displaying locally significant correlations (at the 95% confidence level) between ͗SIE*͘ and global temperature is significantly larger, at the 99.5% confidence level, than the fraction expected given quasiperiodic colored noise in place of the ͗SIE*͘. Based on EOF analysis and multiplicity theory, the four teleconnection patterns the authors found are the ones reflecting correlations most likely to be physically meaningful.

Abstract.This study investigates the nature of interannual variability of Antarctic sea ice and its relationship with the tropical climate. We find that the dominant interannual variance structure in the sea ice edge and surface air temperature fields is organized as a quasi-stationary wave which we call the "Antarctic Dipole" (ADP). It is charac-

We present the first densely-sampled hydrographic survey of the Amundsen Sea Polynya (ASP) region, including a detailed characterization of its freshwater distributions. Multiple components contribute to the freshwater budget, including precipitation, sea ice melt, basal ice shelf melt, and iceberg melt, from local and non-local sources. We used stable oxygen isotope ratios in seawater (d 18 O) to distinguish quantitatively the contributions from sea ice and meteoric-derived sources. Meteoric fractions were high throughout the winter mixed layer (WML), with maximum values of 2-3% (±0.5%). Because the ASP region is characterized by deep WMLs, column inventories of total meteoric water were also high, ranging from 10-13 m (±2 m) adjacent to the Dotson Ice Shelf (DIS) and in the deep trough to 7-9 m (±2 m) in shallower areas. These inventories are at least twice those reported for continental shelf waters near the western Antarctic Peninsula. Sea ice melt fractions were mostly negative, indicating net (annual) sea ice formation, consistent with this area being an active polynya. Independently determined fractions of subsurface glacial meltwater (as one component of the total meteoric inventory) had maximum values of 1-2% (±0.5%), with highest and shallowest maximum values at the DIS outflow (80-90 m) and in iceberg-stirred waters (150-200 m). In addition to these upwelling sites, contributions of subsurface glacial meltwater could be traced at depth along the ~ 27.6 isopycnal, from which it mixes into the WML through various processes. Our results suggest a quasi-continuous supply of melt-laden iron-enriched seawater to the euphotic zone of the ASP and help to explain why the ASP is Antarctica's most biologically productive polynya per unit area.

[1] This study investigates the influence of high-latitude climate variability on the Antarctic sea ice distribution. The climate variability examined here includes distinct climate modes, such as the Southern Annular Mode (SAM), quasi-stationary wave-3 pattern, Pacific South American pattern (PSA) and Semi-Annual Oscillation (SAO). The results reveal that the largest impact comes from PSA in the Antarctic Dipole (ADP) region of the western hemisphere at the interannual timescale, which is related to the teleconnection of El NiñoÀSouthern Oscillation (ENSO). The wave-3 pattern also has a strong and similar influence on sea ice in the ADP regions as PSA does, suggesting a positive interaction between PSA and wave-3 in the region. Measured by correlation coefficients and their significance, SAM has a relatively less significant influence on sea ice than other climate patterns in general, though this global assessment may not apply to particular regions. Sea ice usually responds to large-scale atmospheric anomalies with a 2-month delay. The singular value decomposition (SVD) analysis reveals that the coupled relationships between sea ice and atmospheric pressure, temperature, and wind fields are represented by these known climate modes. The leading coupled modes between sea ice and sea level pressure are accountable for 50% to 60% of total squared covariance for all seasons. The leading modes between sea ice and surface air temperature in winter and summer are also accountable for the same amount of total squared covariance. It indicates that these well-established climate modes/patterns are the dominant factors leading to a strong interaction between the atmosphere and sea ice field in the Antarctic.

The thinning and acceleration of the West Antarctic Ice Sheet has been attributed to basal melting induced by intrusions of relatively warm salty water across the continental shelf. A hydrographic section including lowered acoustic Doppler current profiler measurements showing such an inflow in the channel leading to the Getz and Dotson Ice Shelves is presented here. The flow rate was 0.3-0.4 Sv (1 Sv [ 10 6 m 3 s 21 ), and the subsurface heat loss was estimated to be 1.2-1.6 TW. Assuming that the inflow persists throughout the year, it corresponds to an ice melt of 110-130 km 3 yr 21 , which exceeds recent estimates of the net ice glacier ice volume loss in the Amundsen Sea. The results also show a 100-150-m-thick intermediate water mass consisting of Circumpolar Deep Water that has been modified (cooled and freshened) by subsurface melting of ice shelves and/or icebergs. This water mass has not previously been reported in the region, possibly because of the paucity of historical data.

Evidence of El Niño‐Southern Oscillation (ENSO) teleconnections in the southern high latitude climate has been identified, although the mechanisms that might lead to such far‐reaching teleconnections remain unresolved. Here we propose one such mechanism‐the regional mean meridional atmospheric circulation (the regional Ferrel Cell)‐responsible for the covariability of the ENSO and Antarctic Dipole (ADP; a predominant interannually‐varying signal in the southern high latitudes). It is found that the altered storm tracks associated with the ENSO variability influence the regional Ferrel Cell indirectly by changing the meridional eddy heat flux divergence and convergence, and shifting the latent heat release zone. The changes of the regional Ferrel Cell then influence the southern high latitude climate by modulating the mean meridional heat flux.