What was done
Over the course of several field seasons, the authors mapped the distribution and elevation of surficial deposits along the southern Scott Coast of Antarctica in the vicinity of the Wilson Piedmont Glacier, which runs parallel to the coast of the western Ross Sea from McMurdo Sound north to Granite Harbor.  The chronology of the raised beaches was determined from more than 60 ¹⁴C dates of incorporated organic materials they had previously collected from hand-dug excavations (Hall and Denton, 1999).  They also evaluated more recent changes in snow and ice cover based on aerial photography and observations carried out since the late 1950s.

What was learned
Near the end of the Medieval Warm Period - "as late as 890 ¹⁴C yr BP," as the authors put it - "the Wilson Piedmont Glacier was still less extensive than it is now."  Hence, they rightly conclude the glacier had to have advanced within the last several hundred years, although they note that its eastern margin has retreated "within the last 50 years."

The authors also report a number of similar observations by other investigators.  Citing evidence collected by Baroni and Orombelli (1994a), they note there was "an advance of at least one kilometer of the Hell's Gate Ice Shelf ... within the past few hundred years."  And they report that Baroni and Orombelli (1994b) "documented post-fourteenth century advance of a glacier near Edmonson's Point."  Summarizing these and other findings, they conclude that evidence from the Ross Sea area suggests "late-Holocene climatic deterioration and glacial advance (within the past few hundred years) and twentieth century retreat."

In speaking of the significance of the "recent advance of the Wilson Piedmont Glacier," Hall and Denton report that it "overlaps in time with the readvance phase known in the Alps [of Europe] as the 'Little Ice Age'," which they further note "has been documented in glacial records as far afield as the Southern Alps of New Zealand (Wardle, 1973; Black, 2001), the temperate land mass closest to the Ross Sea region."  They further note that "Kreutz et al. (1997) interpreted the Siple Dome [Antarctica] glaciochemical record as indicating enhanced atmospheric circulation intensity at AD ~1400, similar to that in Greenland during the 'Little Ice Age' (O'Brien et al., 1995)."  In addition, they report that "farther north, glaciers in the South Shetland Islands adjacent to the Antarctic Peninsula underwent a late-Holocene advance, which has been correlated with the 'Little Ice Age' (Birkenmajer, 1981; Clapperton and Sugden, 1988; Martinex de Pison et al., 1996; Bjoreck et al., 1996)."

What it means
The authors note that "the Wilson Piedmont Glacier appears to have undergone advance at approximately the same time as the main phase of the 'Little Ice Age', followed by twentieth-century retreat at some localities along the Scott Coast," although they say "the magnitude of the late-Holocene advance of the Wilson Piedmont Glacier does not approach that of similar-sized glaciers in the Swiss Alps."  Nevertheless, Hall and Denton conclude that "the Wilson Piedmont Glacier record is tantalizing in that it shows glacier advance about the same time as seen in the 'Little Ice Age' elsewhere," which clearly testifies of the global scope of that cold climatic period.

References
Baroni, C. and Orombelli, G.  1994a.  Abandoned penguin rookeries as Holocene paleoclimatic indicators in Antarctica.  Geology 22: 23-26.

Baroni, C. and Orombelli, G.  1994b.  Holocene glacier variations in the Terra Nova Bay area (Victoria Land, Antarctica).  Antarctic Science 6: 497-505.

Birkenmajer, K.  1981.  Lichenometric dating of raised marine beaches at Admiralty Bay, King George Island (South Shetland Islands, West Antarctica).  Bulletin de l'Academie Polonaise des Sciences 29: 119-127.

Bjorck, S., Olsson, S., Ellis-Evans, C., Hakansson, H., Humlum, O. and de Lirio, J.M.  1996.  Late Holocene paleoclimate records from lake sediments on James Ross Island, Antarctica.  Palaeogeography, Palaeoclimatology, Palaeoecology 121: 195-220.

Black, J.  2001.  Can a Little Ice Age Climate Signal Be Detected in the Southern Alps of New Zealand?  MS Thesis, University of Maine.

Clapperton, C.M. and Sugden, D.E.  1988.  Holocene glacier fluctuations in South America and Antarctica.  Quaternary Science Reviews 7: 195-198.

Hall, B.L. and Denton, G.H.  1999.  New relative sea-level curves for the southern Scott Coast, Antarctica: evidence for Holocene deglaciation of the western Ross Sea.  Journal of Quaternary Science 14: 641-650.

Kreutz, K.J., Mayewski, P.A., Meeker, L.D., Twickler, M.S., Whitlow, S.I. and Pittalwala, I.I.  1997.  Bipolar changes in atmospheric circulation during the Little Ice Age.  Science 277: 1294-1296.

Martinez de Pison, E., Serrano, E., Arche, A. and Lopez-Martinez, J.  1996.  Glacial geomorphology.  BAS GEOMAP 5A: 23-27.

O'Brien, S.R., Mayewski, P.A., Meeker, L.D., Meese, D.A., Twickler, M.S. and Whitlow, S.I.  1995.  Complexity of Holocene climate as reconstructed from a Greenland ice core.  Science 270: 1962-1964.

Wardle, P.  1973.  Variations of the glaciers of Westland National Park and the Hooker Range, New Zealand.  New Zealand Journal of Botany 11: 349-388.