In an attempt to rewrite climatic history, certain scientists have claimed that the Little Ice Age and Medieval Warm Period were neither global phenomena nor strong enough where they did occur to have a discernable influence on mean global air temperature, in order to make the putative warming of the last part of the 20th century appear highly unusual, which they equate with anthropogenic-induced, which they associate with the historical rise in the air's CO2 content, which gives them reason to call for dramatic reductions in the use of fossil fuels, which we believe to be unwarranted. Hence, we continually search the emerging scientific literature for evidence that the Little Ice Age and Medieval Warm Period were truly global events. This brief review summarizes what we have learned about the Little Ice Age in Antarctica over the past few years.
Domack et al. (2001) analyzed ocean sediment cores from a prominent depression - the Palmer Deep - located on the inner continental shelf of the western Antarctic Peninsula (64° 51.71' S, 64° 12.47' W) to obtain a high resolution proxy temperature history spanning the past 13,000 years. According to the authors, the proxy records displayed five prominent palaeoenvironmental intervals: (1) a "Neoglacial" cool period beginning 3360 years ago and continuing to the present, (2) a mid-Holocene climatic optimum from 9070 to 3360 years ago, (3) a cool period beginning 11,460 years ago and ending at 9070 years ago, (4) a warm period from 13,180 to 11,460 years ago, and (5) cold glacial conditions prior to 13,180 years ago. Spectral analyses of the data revealed that, superimposed upon these broad climatic intervals, were decadal and centennial-scale temperature cycles. Throughout the current Neoglacial period, the authors report finding "very significant" (above the 99% confidence level) peaks, or oscillations, that occurred at intervals of 400, 190, 122, 85 and 70 years, which they suggest are perhaps driven by solar variability. Additionally, the authors note the presence of a "Little Ice Age" that started about 700 years before present and ended approximately 100 years ago.
Not far away, Khim et al. (2002) analyzed a number of sediment properties and different types of geochemical data obtained from a core removed from the eastern Bransfield Basin just off the northern tip of the Antarctic Peninsula (61°58.9'S, 55°57.4'W). The authors' data clearly depict, as they clearly state, the presence of the "Little Ice Age and Medieval Warm period, together with preceding climatic events of similar intensity and duration." The authors say that "two of the most significant climatic events during the late Holocene are the Little Ice Age (LIA) and Medieval Warm Period (MWP), both of which occurred globally (Lamb, 1965; Grove, 1988)," noting further that "evidence of the LIA has been found in several studies of Antarctic marine sediments (Leventer and Dunbar, 1988; Leventer et al., 1996; Domack et al., 2000)." Indeed, analysis of a sediment core from beneath the Amery Ice Shelf, East Antarctica, suggests that since the cessation of the ice shelf's retreat some 750 14C yr B.P., there has been a major seaward extension of the ice shelf's edge, possibly driven by the cooling associated with the development of the Little Ice Age (Hemer and Harris, 2003).
More evidence that the cold grip of the Little Ice Age enveloped Antarctica comes from the study of Stenni et al. (2002), who examined a number of paleoclimatic indicators in two firn cores that were retrieved from the Talos Dome area of East Antarctica and compared them with those of other East Antarctica ice core records obtained from Dome C EPICA, Taylor Dome and the South Pole. In the words of these authors, the several records "suggest cooler climate conditions between the middle of [the] 16th and the beginning of [the] 19th centuries, which might be related to the Little Ice Age (LIA) cold period." In addition, they documented a decrease in snow accumulation rate "during part of the LIA followed by an increment of about 11% in accumulation during the 20th century." After discussing still other findings, the authors conclude that "more and more evidence coming from ice core records, glacier extension and other proxy records are leading to the idea that the Antarctic continent or at least East Antarctica also experienced the LIA cool episode."
Lastly, we note the study of Hall and Denton (2002), who, over the course of several field seasons, 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. 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)."
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.
In conclusion, it is clear that the emerging scientific literature continues to report ever more evidence for the occurrence of the Little Ice Age in Antarctica, in contradiction of the claims of climate alarmists that this climatic interval was localized to regions about the North Atlantic Ocean. Such literature also highlights the inherent natural variability of climate, and suggests the high probability that recent 20th century warming is not of anthropogenic origin, but the result of natural variability, as the earth has recovered from the now-demonstrated global chill of the Little Ice Age.
References
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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.
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