December 23, 2011

A testable model addressing the issue of East Antarctica ice sheet stability?

Filed under: Letters from Ionia — Tags: , , , — zankaon @ 2:00 am

A considerable portion of E. Antarctica ice (average of 1.6 km height) rests on bedrock of 2000+ ft above sea level. Ice and water tend to flow down hill. Also at least 150+ sub-glacial lakes, and also ice streams, have been detected at the base of such ice sheet.…ture05554.html How stable is such basal environment? We have a current partial snapshot of such watery world; but no temporal context of 50, 100, or 15,000 yrs. of Holocene. Would such basal world seem isolated from topside weather and climate? Might circum-polar current temperature have any indirect effect? Or does just mass of ice sheet account for such watery world? If the latter were so, then glacial vs inter-glacial period would seem to have no relevancy, other than adding or subtracting mass. How might one ascertain whether or not all of E. Antarctica melted or sustained catastrophic fracturing (ice cube effect); resulting in elevated sea level of perhaps ~180 ft.? Might a 10,000+ ft core sample from the Isthmus of Panama indicate whether or not breaching of such isthmus has occurred, due to elevated sea level? Such 50 mi isthmus (maximum elevation of 84 ft.) formed 3 million years ago, from sea bottom uplift, together with subsequent erosive fill.
Would such a core suffice to cover enough glacial and inter-glacial periods; giving an adequate sample? Would any evidence of oceanic sediment, current flows, foraminifora etc. be consistent with breaching of such isthmus; hence consistent with significant sea level elevation, consistent with E. Antarctica dissolution? Would there be any other possible causes of significant sea level elevation? Might we thus have a historical record of whether or not E. Antarctica is stable; using the Isthmus of Panama as our proxy?
Some studies are consistent with the isthmus being closed since at least Miocene times. (2) Other studies are supportive of lower sea levels, cooling, and increased glaciation for ~2.5-2.7 Myrs ago (1). Hence consistent with non-dissolution of East Antarctic ice sheet.
Rohling E.J., Foster G.L., Grant K.M., Marino G., Roberts A.P., Tamisiea M.E., Williams F., Nature Vol 508, April 24, 2014, p. 477, and references therein.
Montes C., Cardona A. Jaramillo C. et al, Middle Miocene closure of the Central American Seaway, Science vol 348 issue 6231 April 10, 2015, and references therein.

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