scholarly journals Variability in retention of Calanus finmarchicus in the Nordic Seas

2005 ◽  
Vol 62 (7) ◽  
pp. 1301-1309 ◽  
Author(s):  
Thomas Torgersen ◽  
Geir Huse
Keyword(s):  
Interannual Variability ◽  
Retention Index ◽  
Vertical Migration ◽  
Barents Sea ◽  
Calanus Finmarchicus ◽  
Nordic Seas ◽  
Physical Forcing ◽  
The Barents Sea ◽  
Initial Location ◽  
Number Of Particles

Abstract Using a regional ocean circulation model and particle tracking, we have studied the probability of the copepod Calanus finmarchicus being retained within the Nordic Seas' population as a function of its initial location, its vertical migration pattern, and the interannual variability in physical forcing. Defining a retention index in terms of the number of particles remaining within the Nordic Seas divided by the initial number of particles released, we found that spatial location had the greatest effect on the retention index during the study period, 1988–1991. Variability as a result of differences in physical forcing among years and among different seasonal vertical migration patterns had smaller but similar effects. The seasonal vertical migration behaviours with the highest advective loss rates and the most sensitive to interannual physical forcing were those that ascended early and descended late from a shallow summer depth. Average retention within the Nordic Seas was 0.40 after one year in simulations with diffusion and advection, and 0.42 in simulations with advection only. The average retention at the end of the four-year sequence was 0.10 and 0.12 with and without diffusion, respectively. Particles located in the western areas of the Nordic Seas had the highest retention, while those along the Norwegian coast showed little or no retention after four years. Initial location has a larger influence on retention than interannual variability in advective fields. C. finmarchicus offspring tend to reside in areas different from their parents, with different probabilities of retention. This spatial variability in retention rate is also experienced as inter-generational variability by members of the population. Model results suggest that almost all of the C. finmarchicus that are advected into the Barents Sea originate from off the Norwegian coast. Thus, predicting C. finmarchicus inflow into the Barents Sea requires knowledge of their abundance on the Norwegian Shelf.

scholarly journals Contribution of Calanus species to the mesozooplankton biomass in the Barents Sea

2017 ◽  
Vol 75 (7) ◽  
pp. 2342-2354 ◽  
Author(s):  
Johanna Myrseth Aarflot ◽  
Hein Rune Skjoldal ◽  
Padmini Dalpadado ◽  
Mette Skern-Mauritzen
Keyword(s):  
Barents Sea ◽  
Zooplankton Community ◽  
Zooplankton Biomass ◽  
Calanus Finmarchicus ◽  
The Arctic ◽  
Arctic Water ◽  
Mesozooplankton Biomass ◽  
The Barents Sea ◽  
Main Driver ◽  
Calanus Species

Abstract Copepods from the genus Calanus are crucial prey for fish, seabirds and mammals in the Nordic and Barents Sea ecosystems. The objective of this study is to determine the contribution of Calanus species to the mesozooplankton biomass in the Barents Sea. We analyse an extensive dataset of Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus, collected at various research surveys over a 30-year period. Our results show that the Calanus species are a main driver of variation in the mesozooplankton biomass in the Barents Sea, and constitutes around 80% of the total. The proportion of Calanus decreases at low zooplankton biomass, possibly due to a combination of advective processes (low C. finmarchicus in winter) and size selective foraging. Though the Calanus species co-occur in most regions, C. glacialis dominates in the Arctic water masses, while C. finmarchicus dominates in Atlantic waters. The larger C. hyperboreus has considerably lower biomass in the Barents Sea than the other Calanus species. Stages CIV and CV have the largest contribution to Calanus species biomass, whereas stages CI-CIII have an overall low impact on the biomass. In the western area of the Barents Sea, we observe indications of an ongoing borealization of the zooplankton community, with a decreasing proportion of the Arctic C. glacialis over the past 20 years. Atlantic C. finmarchicus have increased during the same period.

A satellite-based Lagrangian perspective on Atlantic Water fractionation in the Nordic Seas

2020 ◽  
Author(s):  
Léon Chafik ◽  
Sara Broomé
Keyword(s):  
Arctic Ocean ◽  
Barents Sea ◽  
Bottom Topography ◽  
Atlantic Water ◽  
The Arctic ◽  
Fram Strait ◽  
Nordic Seas ◽  
The Barents Sea ◽  
The Arctic Ocean ◽  
Outer Branch

<p>The Arctic Ocean has been receiving more of the warm and saline Atlantic Water in the past decades. This water mass enters the Arctic Ocean via two Arctic gateways: the Barents Sea Opening and the Fram Strait. Here, we focus on the fractionation of Atlantic Water at these two gateways using a Lagrangian approach based on satellite-derived geostrophic velocities. Simulated particles are released at 70N at the inner and outer branch of the North Atlantic current system in the Nordic Seas. The trajectories toward the Fram Strait and Barents Sea Opening are found to be largely steered by the bottom topography and there is an indication of an anti-phase relationship in the number of particles reaching the gateways. There is, however, a significant cross-over of particles from the outer branch to the inner branch and into the Barents Sea, which is found to be related to high eddy kinetic energy between the branches. This cross-over may be important for Arctic climate variability.</p>

Calanus finmarchicus abundance, production and population dynamics in the Barents Sea in a future climate

2014 ◽  
Vol 125 ◽  
pp. 26-39 ◽  
Author(s):  
G. Skaret ◽  
P. Dalpadado ◽  
S.S. Hjøllo ◽  
M.D. Skogen ◽  
E. Strand
Keyword(s):  
Population Dynamics ◽  
Barents Sea ◽  
Future Climate ◽  
Calanus Finmarchicus ◽  
The Barents Sea

scholarly journals Barents Sea thermal frontal zones variability in 1960–2018

Trudy VNIRO ◽  
2020 ◽  
Vol 180 ◽  
pp. 60-71
Author(s):  
V. A. Ivshin ◽  
A. G. Trofimov ◽  
O. V. Titov
Keyword(s):  
Temperature Gradient ◽  
Interannual Variability ◽  
Barents Sea ◽  
Temperature Gradients ◽  
The Barents Sea ◽  
Mean Temperature ◽  
Frontal Zones ◽  
The 1960S ◽  
Centers Of Mass ◽  
Grid Nodes

This paper discusses our research on the interannual variability in the Barents Sea thermal frontal zones. The length index of the thermal frontal zones (the number of grid nodes with a relevant temperature gradient) and their mean temperature gradients at 50 m depth in August-September 1960–2018 were calculated for an area between 73–78°N, 15–43°E, where the frontal zones are more evident. Thermal frontal zones were identified in the areas where temperature gradients exceeded 0.04 °C/km. Since the beginning of this century, the length index of thermal frontal zones in the Barents Sea has been decreasing and temperature gradients in them have been weakening; in 2010, the length index of frontal zones and the mean temperature gradient reached record low values since 1960. To estimate interannual variability in the positions of thermal frontal zones, their geographical centroids (weighted centers of mass for grid nodes with a relevant temperature gradient) were calculated, taking into account horizontal temperature gradients as weighting coefficients. From the 1960s to the 2010s, the decadal mean centroids of frontal zones shifted northeastwards by 150 km.

Barents Sea thermal frontal zones in 1960–2017: variability, weakening, shifting

2019 ◽  
Vol 76 (Supplement_1) ◽  
pp. i3-i9
Author(s):  
Viktor A Ivshin ◽  
Alexander G Trofimov ◽  
Oleg V Titov
Keyword(s):  
Interannual Variability ◽  
Barents Sea ◽  
Temperature Gradients ◽  
The Barents Sea ◽  
Mean Temperature ◽  
Frontal Zones ◽  
The 1960S

Abstract This paper discusses our research on the interannual variability in the Barents Sea thermal frontal zones. The extent of the frontal zones and their mean temperature gradients at 50 m depth in August–September 1960–2017 were estimated for an area between 73–78°N and 15–43°E, where the frontal zones are more evident. Thermal frontal zones were identified in areas where temperature gradients exceeded 0.04°C km−1. Since the beginning of this century, the extent of the frontal zones has been decreasing and temperature gradients have been weakening. From the 1960s to the 2010s, the decadal mean centroids of thermal frontal zones shifted northeastwards by 150 km.

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