Influence of the uncertainty of the sea level data for the Pleistocene glacial cycles on the analysis of the subsea sediments thermal state

The estimates of the uncertainty for the model simulated subsea permafrost characteristics relative to the uncertainty of paleoclimatic reconstructions of ocean level are obtained. This is done by using the model for thermophysical processes in the subsea sediments. This model is driven by four time series of temperature at the sediment top, TB, which is constructed for the last 400 kyr by using different combinations of the same reconstruction of the past surface air temperature but different sea level reconstructions. At each time instant t and each variable Y, the uncertainty metric is defined as a ratio ▵Y (t) / Ym(t), where ▵Y (t) is spread of the values of Y for different TB time series, and Ym(t) is the mean of Y over different realizations corresponding to different TB. The root-mean-square calculated value of thus defined metric for different time intervals is ≤ 50% for permafrost base depth with the exception of isolated time intervals and / or the deepest part of the shelf. This uncertainty is not symmetric with respect to the sign of the sea level uncertainty. In turn, uncertainty for the hydrate stability zone thickness is small for shallow shelf but becomes pronounced for intermediate and deep shelves. The most uncertainty is due to uncertainty of dates for oceanic regressions and transgressions.

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