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A Riccati model for Denmark Strait overflow variability
Author(s) -
Käse R. H.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl026915
Subject(s) - hindcast , inflow , outflow , hydrography , forcing (mathematics) , noise (video) , constant (computer programming) , environmental science , current meter , geology , climatology , meteorology , oceanography , physics , artificial intelligence , computer science , image (mathematics) , programming language
A controlled volume box model of the western basins of the Nordic Seas for water denser than 1027.8 kg m −3 is constructed, where accumulation in volume () is driven by net imbalances between prescribed net inflow from the northern, eastern and top boundaries ( Q s ) and hydraulically limited outflow through the Denmark Strait. The resulting Riccati equation is solved analytically for filling and flushing experiments with constant Q s and numerically for stochastic forcing Q s ( t ). For small perturbations to Q s with white noise spectrum, the overflow response is red noise with a time scale between 5 and 15 years depending on the mean interface height and area. For Q s proportional to the NAO index, the overflow is positively correlated with the NAO. A 140 years integration reveals variations in the overflow between 2.5 Sv in the 1970s and a maximum of 4 Sv in the 1990s. Hydraulic transport calculations from hydrographic data north of Iceland show good agreement with the model hindcast.