Faglige interesser
- Havets dynamikk ved høye breddegrader
- Baroklin instabilitet og virveldynamikk
- Numerisk havmodellering
Undervisning
Emneord:
Oseanografi
Publikasjoner
-
Sterl, Miriam F.; Lacasce, Joseph Henry; Groeskamp, Sjoerd; Nummelin, Aleksi Henrynpoika; Isachsen, Pål Erik & Baatsen, Michiel L. J.
(2024).
Suppression of mesoscale eddy mixing by topographic PV gradients.
Journal of Physical Oceanography.
ISSN 0022-3670.
doi:
10.1175/JPO-D-23-0142.1.
-
-
Espenes, Håvard; Isachsen, Pål Erik & Nøst, Ole Anders
(2023).
Observations and modeling of tidally generated high-frequency velocity fluctuations downstream of a channel constriction.
Ocean Science.
ISSN 1812-0784.
19(6),
s. 1633–1648.
doi:
10.5194/os-19-1633-2023.
Fulltekst i vitenarkiv
Vis sammendrag
We investigate data from an acoustic Doppler current profiler deployed in a constricted ocean channel showing a tidally dominated flow with intermittent velocity extrema during outflow from the constriction but not during inflow. A 2D numerical ocean model forced by tides is used to examine the spatial flow structure and underlying dynamical processes. We find that flow-separation eddies generated near the tightest constriction point form a dipole pair which propagates downstream and drives the observed intermittent flow variability. The eddies, which are generated by an along-channel adverse pressure gradient, spin up for some time near the constriction until they develop local low pressures in their centers that are strong enough to modify the background along-channel pressure gradient significantly. When the dipole has propagated some distance away from the constriction, the conditions for flow separation are recovered, and new eddies are formed.
-
-
-
Børve, Eli; Isachsen, Pål Erik & Nøst, Ole Anders
(2021).
Rectified tidal transport in Lofoten–Vesterålen, northern Norway.
Ocean Science.
ISSN 1812-0784.
17(6),
s. 1753–1773.
doi:
10.5194/os-17-1753-2021.
Fulltekst i vitenarkiv
Vis sammendrag
Vestfjorden in northern Norway, a major spawning ground for the northeast Arctic cod, is sheltered from the continental shelf and open ocean by the Lofoten–Vesterålen archipelago. The archipelago, however, is well known for hosting strong and vigorous tidal currents in its many straits, currents that can produce significant time-mean tracer transport from Vestfjorden to the shelf outside. We use a purely tidally driven unstructured-grid ocean model to look into non-linear tidal dynamics and the associated tracer transport through the archipelago. Of particular interest are two processes: tidal pumping through the straits and tidal rectification around islands. The most prominent tracer transport is caused by tidal pumping through the short and strongly non-linear straits Nordlandsflaget and Moskstraumen near the southern tip of the archipelago. Here, tracers from Vestfjorden are transported tens of kilometers westward out on the outer shelf. Further north, weaker yet notable tidal pumping also takes place through the longer straits Nappstraumen and Gimsøystraumen. The other main transport route out of Vestfjorden is south of the island of Røst. Here, the transport is primarily due to tracer advection by rectified anticyclonic currents around the island. There is also an anticyclonic circulation cell around the island group Mosken–Værøy, and both cells have flow speeds up to 0.2 m s−1, magnitudes similar to the observed background currents in the region. These high-resolution simulations thus emphasize the importance of non-linear tidal dynamics for transport of floating particles, like cod eggs and larvae, in the region.
-
Dugstad, Johannes Sandanger; Isachsen, Pål Erik & Fer, Ilker
(2021).
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations.
Ocean Science.
ISSN 1812-0784.
17(3),
s. 651–674.
doi:
10.5194/os-17-651-2021.
Fulltekst i vitenarkiv
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Carrasco, Ana; Semedo, Alvaro; Isachsen, Pål Erik; Christensen, Kai H. & Saetra, Øyvind
(2014).
Global surface wave drift climate from ERA-40: The contributions from wind-sea and swell.
Ocean Dynamics.
ISSN 1616-7341.
64(12),
s. 1815–1829.
doi:
10.1007/s10236-014-0783-9.
-
Wang, Keguang; Debernard, Jens; Sperrevik, Ann Kristin; Isachsen, Pål Erik & Lavergne, Thomas
(2013).
A combined optimal interpolation and nudging scheme to assimilate OSISAF sea-ice concentration into ROMS.
Annals of Glaciology.
ISSN 0260-3055.
54(62),
s. 8–12.
doi:
10.3189/2013AoG62A138.
-
Isachsen, Pål Erik; Drivdal, Magnus; Eastwood, Steinar; Gusdal, Yvonne; Noer, Gunnar & Saetra, Øyvind
(2013).
Observations of the ocean response to cold air outbreaks and polar lows over the Nordic Seas.
Geophysical Research Letters.
ISSN 0094-8276.
40(14),
s. 3667–3671.
doi:
10.1002/grl.50705.
-
-
-
Isachsen, Pål Erik & Nøst, Ole Anders
(2012).
The air-sea transformation and residual overturning circulation within the Nordic Seas.
Journal of Marine Research.
ISSN 0022-2402.
70,
s. 31–68.
doi:
10.1357/002224012800502372.
-
Mauritzen, Cecilie; Hansen, Edmond; Andersson, Maria Helena; Berx, Barbara; Beszczynska-Möller, Agnieszka & Burud, Ingunn
[Vis alle 41 forfattere av denne artikkelen]
(2011).
Closing the loop - Approaches to monitoring the state of the Arctic Mediterranean during the International Polar Year 2007-2008.
Progress in Oceanography.
ISSN 0079-6611.
90(1-4),
s. 62–89.
doi:
10.1016/j.pocean.2011.02.010.
-
Isachsen, Pål Erik
(2011).
Baroclinic instability and eddy tracer transport across sloping bottom topography: How well does a modified Eady model do in primitive equation simulations?
Ocean Modelling.
ISSN 1463-5003.
39,
s. 183–199.
doi:
10.1016/j.ocemod.2010.09.007.
-
Lacasce, Joseph Henry & Isachsen, Pål Erik
(2010).
The linear models of the ACC.
Progress in Oceanography.
ISSN 0079-6611.
84(3-4),
s. 139–157.
doi:
10.1016/j.pocean.2009.11.002.
-
-
Bekkeby, Trine; Nilsson, H. C.; Olsgard, F.; Rygg, B.; Isachsen, Pål Erik & Isæus, Martin
(2008).
Identifying soft sediments at sea using GIS-modelled predictor variables and Sediment Profile Image (SPI)
measured response variables.
Estuarine, Coastal and Shelf Science.
ISSN 0272-7714.
79,
s. 631–636.
-
-
Bekkeby, Trine; Isachsen, Pål Erik; Isæus, Martin & Bakkestuen, Vegar
(2008).
GIS modeling of wave exposure at the seabed: A depth-attenuated wave exposure model.
Marine Geodesy.
ISSN 0149-0419.
31,
s. 117–127.
-
Lacasce, Joseph Henry & Isachsen, Pål Erik
(2007).
On Sverdrup discontinuities and vortices in the Southwest Indian Ocean.
Journal of Physical Oceanography.
ISSN 0022-3670.
37,
s. 2940–2950.
-
-
-
Isachsen, Pål Erik; LaCasce, Joe H; Mauritzen, Cecilie & Hakkinen, Sirpa
(2003).
Wind-driven variability of the large-scale recirculating flow in the Nordic seas and Arctic Ocean.
Journal of Physical Oceanography.
ISSN 0022-3670.
33(12),
s. 2534–2550.
-
Stevens, Craig L.; Hurd, Catriona L. & Isachsen, Pål Erik
(2003).
Modeling Diffusion Boundary-Layers in Subtidal Macroalgal Canopies: The Response to Waves and Currents.
Aquatic Sciences.
ISSN 1015-1621.
65(1),
s. 81–91.
-
Nøst, Ole Anders & Isachsen, Pål Erik
(2003).
The large-scale time-mean ocean circulation in the Nordic Seas
and Arctic Ocean estimated from simplified dynamics.
Journal of Marine Research.
ISSN 0022-2402.
61(2),
s. 175–210.
-
Winther, Jan-Gunnar; Godtliebsen, Fred; Gerland, Sebastian & Isachsen, Pål Erik
(2002).
Surface albedo in Ny-Ålesund, Svalbard: variability and trends during 1981--1997.
Global and Planetary Change.
ISSN 0921-8181.
32,
s. 127–139.
-
Isachsen, Pål Erik & Pond, Stephen
(2000).
The influence of the spring-neap tidal cycle on currents and
density in Burrard Inlet, British Columbia, Canada.
Estuarine, Coastal and Shelf Science.
ISSN 0272-7714.
51,
s. 317–330.
Se alle arbeider i Cristin
-
Nummelin, Aleksi Henrynpoika & Isachsen, Pål Erik
(2023).
Improving simulations of the Arctic Ocean with a topography aware mesoscale eddy parameterization.
-
Dugstad, Johannes Sandanger; Koszalka, I.; Dagestad, Knut-Frode; Fer, Ilker & Isachsen, Pål Erik
(2020).
Mass exchange of Atlantic Water with the Lofoten Basin derived from high-resolution Lagrangian simulations .
-
Simonsen, Magne; Lind, Ole Christian; Sætra, Øyvind; Isachsen, Pål Erik; Teien, Hans-Christian & Albretsen, Jon
[Vis alle 7 forfattere av denne artikkelen]
(2019).
Impact of dynamic speciation in model simulations of river-discharged radionuclides in the marine environment.
-
Stige, Leif Christian; Kløver, Geir Olav; Dupont, Nicolas; Borgå, Katrine; Stenseth, Nils Christian & Isachsen, Pål Erik
[Vis alle 7 forfattere av denne artikkelen]
(2019).
Kunnskap fra isødet.
Vis sammendrag
Åpent arrangement med disse foredragene: "Kunnskapsinnhøsting i Arktis ombord i Fram 1893-1896" (Kløver); "Arven etter Nansen" (Stige); "Hva skjer med økosystemet når sjøisen forsvinner?" (Dupont); "Miljøgifter i Arktis" (Borgå); "Havstrømmene i Arktis – hvorfor er de spesielle?" (Isachsen); "En djerv polarforsker: Hanna Resvoll-Holmsen (1873-1943)" (Sandberg). Ordstyrere: Stige og Stenseth.
-
Dugstad, Johannes Sandang; Koszalka, Inga; Isachsen, Pål Erik; Dagestad, Knut-Frode; Fer, Ilker & Lacasce, Joseph Henry
(2019).
Mass exchange of Atlantic Water with the Lofoten Basin derived from high resolution Lagragian simulations and Eulerian models.
-
Simonsen, Magne; Saetra, Øyvind; Isachsen, Pål Erik; Lind, Ole Christian; Skjerdal, Hilde Kristin & Salbu, Brit
[Vis alle 8 forfattere av denne artikkelen]
(2017).
The impact of tidal and mesoscale eddy advection on the long term dispersion of 99Tc from Sellafield.
-
Simonsen, Magne; Isachsen, Pål Erik; Sætra, Øyvind; Lind, Ole Christian; Salbu, Brit & Skjerdal, Hilde Kristin
(2016).
Long-term dispersion of radioactive 99Tc from Sellafield - the impact of resolution.
-
Simonsen, Magne; Isachsen, Pål Erik; Sætra, Øyvind; Salbu, Brit; Lind, Ole Christian & Bartnicki, Jerzy
[Vis alle 7 forfattere av denne artikkelen]
(2014).
Marine radionuclide transport in the northern North Atlantic estimated with an eddy-permitting ocean model.
-
Røed, Lars Petter; Kristensen, Nils Melsom; Isachsen, Pål Erik & Sætra, Øyvind
(2013).
The triply nested Norwegian numerical ocean weather prediction system: Problems and possible solutions.
-
Røed, Lars Petter; Brostrøm, Gøran; Isachsen, Pål Erik; Kristensen, Nils Melsom & Engedahl, Harald
(2011).
Numerical Ocean Weather Prediction: A quest for computer power and capacity.
META.
ISSN 1890-1956.
s. 28–31.
Vis sammendrag
To predict the drift and spreading of nutrients, algae blooms, oil and contaminants in the ocean, one of the key elements besides wind and waves is accurate predictions of ocean currents, temperature and salinity or “ocean weather”. The same is true regarding drift of floating objects such as ships, small crafts, containers, man overboard, icebergs and sea-ice. In addition such predictions are of crucial importance for the offshore industry, fisheries and for marine operations in general. The prediction of the ocean weather is, however, a continuous quest for more computer power and capacity.
-
Se alle arbeider i Cristin
Publisert
13. jan. 2016 16:12
- Sist endret
14. nov. 2022 15:15