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Yunfang
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Yunfang
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ArticleEffects of interannual environmental variability on the transport-retention dynamics in haddock Melanogrammus aeglefinus larvae on Georges Bank(Inter-Research, 2013-07-30) Boucher, Jason M. ; Chen, Changsheng ; Sun, Yunfang ; Beardsley, Robert C.Georges Bank is a region of high biological productivity characterized by a well-defined clockwise tidal rectified circulation gyre. Fluctuations in the year-class strength of haddock Melanogrammus aeglefinus on Georges Bank have been attributed to mortality during the highly vulnerable larval stages. While predation and starvation greatly impact on survival, advection to unfavorable regions may result in greatly reduced numbers of individuals. For successful self-recruitment to occur, individuals must remain within the shoal region of Georges Bank until settlement. An individual-based model (IBM) was utilized to estimate the retention of haddock eggs and larvae on Georges Bank annually for 1995 through 2009. The IBM was driven by the Finite-Volume Community Ocean Model (FVCOM) for the Gulf of Maine domain. Biological components of haddock larvae were omitted to restrict analyses to the impact of circulation on passive transport. Inflow over the Scotian Shelf and tidal interaction patterns were identified as the major drivers of variability in interannual transport-retention dynamics. The simulations indicated that retention rates were highest in 2000 and 2003, and lowest in 1997. The above-average retention in 2000 and 2003 with anomalously large recruitment only in 2003 indicates that high retention appears to be necessary but not sufficient to explain large recruitment events of haddock on Georges Bank.
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ArticleTidal dynamics in the Gulf of Maine and New England Shelf : an application of FVCOM(American Geophysical Union, 2011-12-10) Chen, Changsheng ; Huang, Haosheng ; Beardsley, Robert C. ; Xu, Qichun ; Limeburner, Richard ; Cowles, Geoffrey W. ; Sun, Yunfang ; Qi, Jianhua ; Lin, HuichanThe unstructured-grid, Finite-Volume Community Ocean Model (FVCOM) was used to simulate the tides in the Gulf of Maine (GoM) and New England Shelf (NES) for homogeneous and summer stratified conditions. FVCOM captures the near-resonant nature of the semidiurnal tide and energy flux in the GoM and the complex dynamics governing the tide in the NES. Stratification has limited impact on tidal elevation, but can significantly modify the tidal current profile. Internal tides are energetic in the stratified regions over steep bottom topography, but their contribution to the total tidal energy flux is only significant over the northeast flank of Georges Bank. The model suggests that the tidal flushing-induced eddy east of Monomoy Island is the dynamic basis for the locally observed phase lead of the M2 tide. The southward propagating tidal wave east of Cape Cod encounters the northeastward propagating tidal wave from the NES south of Nantucket Island, forming a zone of minimum sea level along a southeast-oriented line from Nantucket Island. These two waves are characterized by linear dynamics in which bottom friction and advection are negligible in the momentum balance, but their superposition leads to a strong nonlinear current interaction and large bottom stress in the zone of lowest sea elevation.
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ArticleImpact of current-wave interaction on storm surge simulation : a case study for Hurricane Bob(John Wiley & Sons, 2013-05-30) Sun, Yunfang ; Chen, Changsheng ; Beardsley, Robert C. ; Xu, Qichun ; Qi, Jianhua ; Lin, HuichanHurricane Bob moved up the U.S. east coast and crossed over southern New England and the Gulf of Maine [with peak marine winds up to 54 m/s (100 mph)] on 19–20 August 1991, causing significant damage along the coast and shelf. A 3-D fully wave-current-coupled finite-volume community ocean model system was developed and applied to simulate and examine the coastal ocean responses to Hurricane Bob. Results from process study-oriented experiments showed that the impact of wave-current interaction on surge elevation varied in space and time, more significant over the shelf than inside the inner bays. While sea level change along the coast was mainly driven by the water flux controlled by barotropic dynamics and the vertically integrated highest water transports were essentially the same for cases with and without water stratification, the hurricane-induced wave-current interaction could generate strong vertical current shear in the stratified areas, leading to a strong offshore transport near the bottom and vertical turbulent mixing over the continental shelf. Stratification could also result in a significant difference of water currents around islands where the water is not vertically well mixed.