TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 61 (No. 4), pp. 733-746, 2005

Sedimentary Responses to an Abrupt Change of Biogenic Silica Flux by a Sediment Model for Long Timescale Simulations

Megumi O. Chikamoto1* and Yasuhiro Yamanaka1,2

1Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
2Frontier Research System for Global Change, Yokohama 236-0001, Japan

(Received 22 March 2004; in revised form 28 November 2004; accepted 29 November 2004)

Abstract: A one-dimensional sediment model was developed by introducing the CIP-CSL2 scheme in the advection term. This enables us to represent fluctuations of the vertical profiles of 100 cm depth, which needs integrations on a longer timescale than 10 kyr, because this scheme avoids smoothing of the vertical profiles due to no numerical diffusion, instead of a commonly used forward scheme. Using the models with 10 and 100 cm depths (hereafter, called the 10 cm model and the 100 cm model, respectively) to predict the contents of biogenic silica and clay, we have evaluated the sedimentary responses to an abrupt change in the biogenic silica rain flux. When the rain flux of biogenic silica abruptly decreases, the 10 cm model underestimates the dissolution flux of biogenic silica compared with the 100 cm model. This is because only clay is supplied from the bottom boundary associated with excess dissolution and also because dissolution of biogenic silica below 10 cm depth is neglected by the 10 cm model. When we consider dissolved matter inputs from sediments to marine biogiochemical cycles, simulations by the 100 cm model would lead to more realistic responses in sediments.

*Corresponding author E-mail: meg@ees.hokudai.ac.jp

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