warm antarctica

here are a few science daily articles on a very much warmer historical antarctica, warmer than the horizontal level in the game.

Snapshot Of Past Climate Reveals No Ice In Antarctica Millions Of Years Ago

ScienceDaily (July 28, 2008) — A snapshot of New Zealand’s climate 40 million years ago reveals a greenhouse Earth, with warmer seas and little or no ice in Antarctica, according to research recently published in the journal Geology.

The study suggests that Antarctica at that time was yet to develop extensive ice sheets. Back then, New Zealand was about 1100 km further south, at the same latitude as the southern tip of South America – so was closer to Antarctica – but the researchers found that the water temperature was 23-25°C at the sea surface and 11-13°C at the bottom.

“This is too warm to be the Antarctic water we know today,” said Dr Catherine (Cat) Burgess from Cardiff University and lead-author of the paper. “And the seawater chemistry shows there was little or no ice on the planet.”

These new insights come from the chemical analysis of exceptionally well preserved fossils of marine micro-organisms called foraminifers, discovered in marine rocks from New Zealand. The researchers tested the calcium carbonate shells from these fossils, which were found in 40 million-year-old sediments on a cliff face at Hampden Beach, South Island.

“Because the fossils are so well preserved, they provide more accurate temperature records.” added Dr Burgess. “Our findings demonstrate that the water temperature these creatures lived in was much warmer than previous records have shown.”

“Although we did not measure carbon dioxide, several studies suggest that greenhouse gases forty million years ago were similar to those levels that are forecast for the end of this century and beyond.

Our work provides another piece of evidence that, in a time period with relatively high carbon dioxide levels, temperatures were higher and ice sheets were much smaller and likely to have been completely absent.”

The rock sequence from the cliff face covers a time span of 70,000 years and shows cyclical temperature variations with a period of about 18,000 years. The temperature oscillation is likely to be related to the Earth’s orbital patterns.

The research was funded by the Natural Environment Research Council, the Netherlands Organisation for Scientific Research (NOW) and GNS Science, New Zealand.

Issued jointly by the Natural Environment Research Council and Cardiff University.

and here’s one that would make antarctica much higher in elevation, a vast china-like continent and the archipelago.

Scientists Propose Antarctic Location For ‘Missing’ Ice Sheet

ScienceDaily (Aug. 25, 2009) — New research by scientists at UC Santa Barbara indicates a possible Antarctic location for ice that seemed to be missing at a key point in climate history 34 million years ago. The research, which has important implications for climate change, is described in a paper published today in Geophysical Research Letters, a journal of the American Geophysical Union.

“Using data from prior geological studies, we have constructed a model for the topography of West Antarctic bedrock at the time of the start of the global climate transition from warm ‘greenhouse’ earth to the current cool ‘icehouse’ earth some 34 million years ago,” explained Douglas S. Wilson, first author and an associate research geophysicist with UCSB’s Department of Earth Science and Marine Science Institute.

Wilson and his co-author, Bruce Luyendyk, a professor in the Department of Earth Science, discovered that, contrary to most current models for bedrock elevations of West Antarctica, the bedrock in the past was of much higher elevation and covered a much larger area than today. Current models assume that an archipelago of large islands existed under the ice at the start of the climate transition, similar to today, but Wilson and Luyendyk found that does not fit their new model. In fact, the authors state that the land area above sea level of West Antarctica was about 25 percent greater in the past.

The existing theory leaves West Antarctica in a minor role in terms of the ice accumulation beginning 34 million years ago. Ice sheet growth on earth is believed to have developed on the higher and larger East Antarctic subcontinent while West Antarctica joined the process later around 14 million years ago. “But a problem exists with leaving West Antarctica out of the early ice history,” said Wilson. “From other evidence, it is believed that the amount of ice that grew on earth at the 34 million year climate transition was too large to be accounted for by formation on East Antarctica alone, the most obvious location for ice sheet growth. Another site is needed to host the extra missing ice.”

Evidence for that large mass of ice comes from two sources: the chemical and isotopic composition in shell material of marine microfossils, which are sensitive to ocean temperatures and the amount of ice on land; and from geologic records of lowered sea level at the time that indicate how much ice formed on land to produce the sea level drop.

The new study, by showing that West Antarctica had a higher elevation 34 million years ago than previously thought, reveals a possible site for the accumulation of the early ice that is unaccounted for. “Preliminary climate modeling by researchers at Pennsylvania State University demonstrates that this new model of higher elevation West Antarctica bedrock topography can indeed host the missing ice,” said Luyendyk. “Our results, therefore, have opened up a new paradigm for the history of the growth of the great global ice sheets. Both East and West Antarctica hosted the growing ice.”

The new hypothesis may solve another conflict among climate scientists. Given that more ice grew than could be hosted on East Antarctica alone, some researchers have proposed that the missing ice formed in the northern hemisphere. This would have been many millions of years before the well-known documentation of ice growth there, which started about three million years ago; evidence for ice sheets in the northern hemisphere prior to that time is not established. The new bedrock model shows it is not necessary to have ice hosted in the northern polar regions at the start of global climate transition; West Antarctica could have accommodated the extra ice.

Maps of Antarctic topography with restorations for removal of the load of modern ice only (left), and additionally for erosion, sedimentation, thermal contraction, and horizontal plate motion in geologically active regions (right). Models correcting only for ice load have been used in all simulations of ice growth to date, but significant changes result from additionally correcting for other geologic processes. (Credit: Image courtesy of University of California – Santa Barbara)
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Posted on December 6, 2011, in antarctica, research. Bookmark the permalink. Leave a comment.

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