Physical and Structural Properties of the Siple Dome Core

Department Of Army Cold Regions Research & Engineering Lab, Vicksburg MS

Investigators

Abstract

This award supports a 2-year renewal program to continue research on the physical and structural properties of the Siple Dome ice core. This work will include continued monitoring of the core relaxation process, additional examination of the volcanic ash and dust record preserved in the Siple Dome core and its relationship to the timing and distribution pattern of widespread infall of tephra in the Byrd core, and possible climatic implications, additional thin sectioning of ice from below 800 m to obtain a more accurate picture of the response of the deeper ice to increased deformation and elevated temperatures, and measurements of total air content in the basal debris-bearing ice to evaluate mechanisms by which debris is incorporated at the bed. Especially intriguing are ongoing attempts to resolve the climate record at Siple Dome and to refine the time scale. Currently, we are working to obtain the best possible depth-age scale that utilizes annual layer counting based on visual stratigraphy and ECM in conjunction with the gas record. Many climate-related records from the Siple Dome core have recently been presented showing a possible hiatus at approximately 680 m and a potential major climatic event at around 720 m. However, the layer structure in the Siple Dome core shows reversed inclined layering as high as 559 m and evidence of disturbed and steeply inclined layering in deeper ice. It is critical that we determine whether this kind of structural disturbance has resulted in discontinuities in the climate record or is some other structural artifact that has not impacted the continuity of the record. In addition to conducting further visual examination of the core, we plan to prepare vertical thick sections in several regions of disturbed ice structure to determine if the crystal structure reveals evidence of deformation. Until this is complete, we will not know how deep into the core a continuous climate record exists.