Title : ANCIENT POLAR FOREST UNDERSCORES ANTARCTICA'S WARMER PAST Type : Press Release NSF Org: OD / LPA Date : November 6, 1992 File : pr9298 Cheryl Dybas November 6, 1992 (202) 357-9498 NSF PR 92-98 ANCIENT POLAR FOREST UNDERSCORES ANTARCTICA'S WARMER PAST Remains of a 260-million-year-old forest of deciduous trees have been found in a region of Antarctica that is today just 400 miles from the South Pole. The discovery of fossilized stumps of Glossopteris, a seed fern now extinct, further supports the view that during the Permian period -- from 250 to 280 million years ago -- Antarctica enjoyed a climate much warmer than it is today, according to Edith Taylor, a National Science Foundation-funded research scientist at Ohio State's Byrd Polar Research Center. Deciduous trees -- trees that lose their leaves yearly -- grow in temperate climes. The remains Taylor studied, found on a ridge of Mt. Achernar in the central Transantarctic Mountains, are at about 82 degrees south latitude. That's the furthest from the equator that a forest has ever been found. During the Permian period, the site was probably located at 80 to 85 degrees south latitude. The discovery of such trees, instead of the short, shrubby conifers one might have expected to find, is further biological evidence to refute the claim some climatologists have offered that the South Pole was frigid during the Permian period, Taylor says. "Some climate models for this region have suggested that winter temperatures averaged minus 30 to minus 40 degrees Celsius and summer temperatures hovered around zero." In contrast, Taylor claims that the climate of the Permian was quite favorable to the growth of deciduous trees. The tree stumps are the preserved remnants of a grove of saplings rooted in a swampy area that eventually became shale and siltstone. Taylor analyzed the stumps, which were found in an area slightly larger than the size of a volleyball court. The distribution of the stumps in this area was much more dense than that of a modern forest. The diameter of stumps ranged from 3.6 to 7.2 inches, and, though the largest stump protruded just 8 inches above ground, Taylor estimates these trees grew to be about 18 feet high. Glossopteris have slender, tongue-shaped leaves that may have been 4 to 8 inches long. After studying the tree rings of the preserved stumps, Taylor estimates the trees were close in age, ranging from 7- to 15-years-old. To study the tree rings, a research team brought back several stump samples to Taylor's lab at Ohio State. After etching the petrified wood with acid, acetone and plastic were used to lift off thin layers of the wood to mount on slides. Then, using a microscope, Taylor measured the width of the tree rings, and found them to be extraordinarily wide. While the average width was about one-fifth of an inch, the largest measured almost one-half inch thick. "These are the thickest rings ever found in a polar climate," says Taylor. "Part of the reason that the plant grew such big rings was that, being near the South Pole, it had 24 hours of light throughout the summer." Also, Taylor found no frost rings, the telltale signs of freezing conditions. "This indicates that there were no hard frosts during the growing season when these trees still had their foliage." Frost rings, which appear as a row of disrupted cells, are essentially scars formed in the early spring and late fall when low temperatures destroy living cells. "The fact that we see no frost rings and that the growth rings are so wide suggests that conditions were not marginal. Temperatures were consistently warm enough for steady growth throughout the summer." But such evidence can't determine the exact temperatures this region experienced. "Biological evidence like this should be included along with the physical parameters (such as wind circulation, temperature, etc.) that are used when producing models of ancient climates," says the scientist.