Description: Fresh deposits above the margins of Reedy Glacier show that maximum ice levels during the last glaciation were several hundred meters above present near the glacier mouth and converged to less than 60 m above the present-day surface at the head of the glacier. Exposure ages of samples from five sites along its margin show that Reedy Glacier and its tributaries thickened asynchronously between 17 and 7 kyr BP At the Quartz Hills, located midway along the glacier, maximum ice levels were reached during the period 17-14 kyr BP. Farther up-glacier the ice surface reached its maximum elevation more recently: 14.7-10.2 kyr BP at the Caloplaca Hills; 9.1-7.7 kyr BP at Mims Spur; and around 7 kyr BP at Hatcher Bluffs. We attribute this time-transgressive behavior to two different processes: At the glacier mouth, growth of grounded ice and subsequent deglaciation in the Ross Sea embayment caused a wave of thickening and then thinning to propagate up-glacier. During the Lateglacial and Holocene, increased snow accumulation on the East Antarctic Ice Sheet caused transient thickening at the head of the glacier. An important result of this work is that moraines deposited along Reedy Glacier during the last ice age cannot be correlated to reconstruct a single glacial maximum longitudinal profile. The profile steepened during deglaciation of the Ross Sea, thinning at the Quartz Hills after 13 kyr BP while thickening upstream. Near its confluence with Mercer Ice Stream, rapid thinning beginning prior to 7-8 kyr BP reduced the level of Reedy Glacier to close to its present level. Thinning over the past 1000 years has lowered the glacier by less than 20 m.

Description: Deposits corresponding to multiple periods of glaciation are preserved in ice-free areas adjacent to Reedy Glacier, southern Transantarctic Mountains. Glacial geologic mapping, supported by 10Be surface-exposure dating, shows that Reedy Glacier was significantly thicker than today multiple times during the mid-to-late Cenozoic. Longitudinal-surface profiles reconstructed from the upper limits of deposits indicate greater thickening at the glacier mouth than at the head during these episodes, indicating that Reedy Glacier responded primarily to changes in the thickness of the West Antarctic Ice Sheet. Surface-exposure ages suggest this relationship has been in place since at least 5 Ma. The last period of thickening of Reedy Glacier occurred during Marine Isotope Stage 2, at which time the glacier surface near its confluence with the West Antarctic Ice Sheet was at least 500 m higher than today.

Description: High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979-2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

Description: The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica’s continental ice volume. Over the last few decades, studies on glacialegeological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23e19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on theWeddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different icesheet models have reconstructed conflicting LGM ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the LGM sealevel low-stand of w130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past icesheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the LGM ice-sheet configuration, including time-slice reconstructions for post- LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacialegeological datasets on Antarctic Ice- Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical icesheet models