Recently, Huizi Dong, the postdoctoral fellow of School of Oceanography, Shanghai Jiao Tong University (SJTU-SOO), published a research article titled “Dynamical Controls of the Eastward Transport of Overwintering Calanus finmarchicus From the Lofoten Basin” as the first author in the authoritative international Journal of Geophysical Research: Oceans.
The paper was completed by the Postdoctor Huizi Dong (first author), Professor Meng Zhou (corresponding author) at SJTU-SOO in in collaboration with Professor Walker O. Smith at SJTU-SOO, Postdoctor Baosheng Li at Second Institute of Oceanography MNR, Associate Researcher Ziyuan Hu at Institute of Oceanology, Chinese Academy of Sciences, Associate Professor Sünnje L. Basedow at UiT the Arctic University of Norway, Researcher Frank Gaardsted at Akvaplan-niva Fram Centre and Associate Professor Zhaoru Zhang and Yisen Zhong at SJTU-SOO.
Diapausing populations of Calanus finmarchicus at depth in the Lofoten Basin (LB) return to the continental shelf and slope off the Lofoten-Vesterålen Islands during the phytoplankton spring bloom to feed and spawn, forming surface swarms with a great abundance. To study how overwintering populations of C. finmarchicus move with the deep currents and return to the shelf, Lagrangian transport characteristics of particles in deep water between 2008 and 2019 were analyzed using Global Ocean Reanalysis and Simulation re-analysis data and Lagrangian Coherent Structures (LCSs). Our analyses revealed that persistent eastward transport of diapausing C. finmarchicus between LB and continental slope occurred mainly between 600 and 1,100 m in the Arctic Intermediate Water. The consistency of the vertical distributions of C. finmarchicus abundance and salinity further suggests that physical factors control the horizontal distribution of the species. Hovmöller diagrams of kinetic energy indicate that there is an eastward advection of mean current at depth. The co-occurrence between the eastward transport of LCSs and the eastward advection of the mean current provides direct evidence that the life history of C. finmarchicus is subjected to physical control in the Norwegian Sea (Figure 1).
Figure 1. Conceptual diagram of the seasonal life cycle of the copepod Calanus finmarchicus in the basin-slope-shelf areas in the northern Norwegian Sea.
This study demonstrates the importance of horizontal transport of overwintering populations from the LB for C. finmarchicus shelf populations and further establishes the region as a key source for the C. finmarchicus population on the Lofoten shelf in early spring. The stability of eastward transport at 600–1,100 m in AIW during winter can play a significant role in transporting diapausing C. finmarchicus to the continental slope each year. This process is a part of the potential regular spatial and temporal closure of C. finmarchicus population at the basin-slope-shelf areas in the northern Norwegian Sea.
The eastward propagation of the MKE is the main dynamical control that results in C. finmarchicus overwintering in the LB to reach the continental slope by early February. Further dynamical diagnostics indicate that nonlocal kinetic energy feeding and energy conversion from eddy to mean currents produce a stable eastward transport mechanism for C. finmarchicus from LB to the continental slope at overwintering depths.
Figure 2. (a)(b) Paths and origins of the water parcels from Lagrangian particle tracking simulations over 60 days superposed on the Global Ocean Reanalysis and Simulation-derived finite-size Lyapunov exponent (FSLE) (d−1) fields. The longitudinal advections for 60 days prior to (c) 11 December 2016, and (d) 1 January 2014.
Figure 3. Hovmöller diagrams of the composite terms for (a) <∂MKE/∂t>, (b) <∂EKE/∂t>, (c)
The research is supported by the Sino-Norwegian Collaborative STRESSOR Project, funded by the Natural Science Foundation of China (NSFC Grant No. 41861134040) and the Research Council of Norway (RCN Grant No. 287043). This study is also supported by the NSFC Special Program (Grant No. 41941008), the Shanghai Frontiers Science Center of Polar Science (SCOPS), and the Overseas Visiting Program for Outstanding PhD Students of Shanghai Jiao Tong University.
Link 1 to the article：
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022JC018909
Link 2 to the article：
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021JC017408
