Articles | Volume 11, issue 5
https://doi.org/10.5194/os-11-743-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/os-11-743-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Transport of volume, heat, and salt towards the Arctic in the Faroe Current 1993–2013
B. Hansen
CORRESPONDING AUTHOR
Faroe Marine Research Institute, Tórshavn, Faroe Islands
K. M. H. Larsen
Faroe Marine Research Institute, Tórshavn, Faroe Islands
H. Hátún
Faroe Marine Research Institute, Tórshavn, Faroe Islands
R. Kristiansen
Faroe Marine Research Institute, Tórshavn, Faroe Islands
E. Mortensen
Faroe Marine Research Institute, Tórshavn, Faroe Islands
S. Østerhus
Uni Research Climate, Bergen, Norway
Related authors
Bogi Hansen, Karin M. H. Larsen, Hjálmar Hátún, Steffen M. Olsen, Andrea M. U. Gierisch, Svein Østerhus, and Sólveig R. Ólafsdóttir
Ocean Sci., 19, 1225–1252, https://doi.org/10.5194/os-19-1225-2023, https://doi.org/10.5194/os-19-1225-2023, 2023
Short summary
Short summary
Based on in situ observations combined with sea level anomaly (SLA) data from satellite altimetry, volume as well as heat (relative to 0 °C) transport of the Iceland–Faroe warm-water inflow towards the Arctic (IF inflow) increased from 1993 to 2021. The reprocessed SLA data released in December 2021 represent observed variations accurately. The IF inflow crosses the Iceland–Faroe Ridge in two branches, with retroflection in between. The associated coupling to overflow reduces predictability.
Sissal Vágsheyg Erenbjerg, Jon Albretsen, Knud Simonsen, Erna Lava Olsen, Eigil Kaas, and Bogi Hansen
Ocean Sci., 17, 1639–1655, https://doi.org/10.5194/os-17-1639-2021, https://doi.org/10.5194/os-17-1639-2021, 2021
Short summary
Short summary
Here, we describe a strait that has narrow and shallow sills in both ends and is close to an amphidromic region. This generates tidally driven flows into and out of the strait, but with very different exchange rates across the entrances in both ends so that it behaves like a mixture between a strait and a fjord. Using a numerical model, we find a fortnightly signal in the net transport through the strait, generated by long-period tides. Our findings are verified by observations.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, Steingrímur Jónsson, Sólveig Rósa Ólafsdóttir, Andreas Macrander, William Johns, N. Penny Holliday, and Steffen Malskær Olsen
Ocean Sci. Discuss., https://doi.org/10.5194/os-2021-14, https://doi.org/10.5194/os-2021-14, 2021
Preprint withdrawn
Short summary
Short summary
Compared to other freshwater sources, runoff from Iceland is small and usually flows into the Nordic Seas. Under certain wind conditions, it can, however, flow into the Iceland Basin and this occurred after 2014, when this region had already freshened from other causes. This explains why the surface freshening in this area became so extreme. The local and shallow character of this runoff allows it to have a disproportionate effect on vertical mixing, winter convection, and biological production.
Svein Østerhus, Rebecca Woodgate, Héðinn Valdimarsson, Bill Turrell, Laura de Steur, Detlef Quadfasel, Steffen M. Olsen, Martin Moritz, Craig M. Lee, Karin Margretha H. Larsen, Steingrímur Jónsson, Clare Johnson, Kerstin Jochumsen, Bogi Hansen, Beth Curry, Stuart Cunningham, and Barbara Berx
Ocean Sci., 15, 379–399, https://doi.org/10.5194/os-15-379-2019, https://doi.org/10.5194/os-15-379-2019, 2019
Short summary
Short summary
Two decades of observations of the Arctic Mediterranean (AM) exchanges show that the exchanges have been stable in terms of volume transport during a period when many other components of the global climate system have changed. The total AM import is found to be 9.1 Sv and has a seasonal variation in amplitude close to 1 Sv, and maximum import in October. Roughly one-third of the imported water leaves the AM as surface outflow.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Steffen Malskær Olsen, Detlef Quadfasel, Kerstin Jochumsen, and Svein Østerhus
Ocean Sci., 14, 871–885, https://doi.org/10.5194/os-14-871-2018, https://doi.org/10.5194/os-14-871-2018, 2018
Short summary
Short summary
The Western Valley is one of the passages across the Iceland–Scotland Ridge through which a strong overflow of cold, dense water has been thought to feed the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), but its strength has not been known. Based on a field experiment with instruments moored across the valley, we show that this overflow branch is much weaker than previously thought and that this is because it is suppressed by the warm countercurrent in the upper layers.
Bogi Hansen, Turið Poulsen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, Svein Østerhus, Elin Darelius, Barbara Berx, Detlef Quadfasel, and Kerstin Jochumsen
Ocean Sci., 13, 873–888, https://doi.org/10.5194/os-13-873-2017, https://doi.org/10.5194/os-13-873-2017, 2017
Short summary
Short summary
On its way towards the Arctic, an important branch of warm Atlantic water passes through the Faroese Channels, but, in spite of more than a century of investigations, the detailed flow pattern through this channel system has not been resolved. This has strong implications for estimates of oceanic heat transport towards the Arctic. Here, we combine observations from various sources, which together paint a coherent picture of the Atlantic water flow and heat transport through this channel system.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, and Svein Østerhus
Ocean Sci., 12, 1205–1220, https://doi.org/10.5194/os-12-1205-2016, https://doi.org/10.5194/os-12-1205-2016, 2016
Short summary
Short summary
The Faroe Bank Channel is one of the main passages for the flow of cold dense water from the Arctic into the depths of the world ocean where it feeds the deep branch of the AMOC. Based on in situ measurements, we show that the volume transport of this flow has been stable from 1995 to 2015. The water has warmed, but salinity increase has maintained its high density. Thus, this branch of the AMOC did not weaken during the last 2 decades, but increased its heat transport into the deep ocean.
S. M. Olsen, B. Hansen, S. Østerhus, D. Quadfasel, and H. Valdimarsson
Ocean Sci., 12, 545–560, https://doi.org/10.5194/os-12-545-2016, https://doi.org/10.5194/os-12-545-2016, 2016
Short summary
Short summary
About half of the warm Atlantic water that enters the Norwegian Sea flows between Iceland and the Faroes. Here it crosses the Iceland-Faroe Ridge and dynamically interacts with the cold, dense and deep return flow across the ridge. This flow is not resolved in climate models and the lack of interaction prevents realistic heat anomaly propagation towards the Arctic.
B. Berx, B. Hansen, S. Østerhus, K. M. Larsen, T. Sherwin, and K. Jochumsen
Ocean Sci., 9, 639–654, https://doi.org/10.5194/os-9-639-2013, https://doi.org/10.5194/os-9-639-2013, 2013
Michael Mayer, Takamasa Tsubouchi, Susanna Winkelbauer, Karin Margretha H. Larsen, Barbara Berx, Andreas Macrander, Doroteaciro Iovino, Steingrímur Jónsson, and Richard Renshaw
State Planet, 1-osr7, 14, https://doi.org/10.5194/sp-1-osr7-14-2023, https://doi.org/10.5194/sp-1-osr7-14-2023, 2023
Short summary
Short summary
This paper compares oceanic fluxes across the Greenland–Scotland Ridge (GSR) from ocean reanalyses to largely independent observational data. Reanalyses tend to underestimate the inflow of warm waters of subtropical Atlantic origin and hence oceanic heat transport across the GSR. Investigation of a strong negative heat transport anomaly around 2018 highlights the interplay of variability on different timescales and the need for long-term monitoring of the GSR to detect forced climate signals.
Bogi Hansen, Karin M. H. Larsen, Hjálmar Hátún, Steffen M. Olsen, Andrea M. U. Gierisch, Svein Østerhus, and Sólveig R. Ólafsdóttir
Ocean Sci., 19, 1225–1252, https://doi.org/10.5194/os-19-1225-2023, https://doi.org/10.5194/os-19-1225-2023, 2023
Short summary
Short summary
Based on in situ observations combined with sea level anomaly (SLA) data from satellite altimetry, volume as well as heat (relative to 0 °C) transport of the Iceland–Faroe warm-water inflow towards the Arctic (IF inflow) increased from 1993 to 2021. The reprocessed SLA data released in December 2021 represent observed variations accurately. The IF inflow crosses the Iceland–Faroe Ridge in two branches, with retroflection in between. The associated coupling to overflow reduces predictability.
Sissal Vágsheyg Erenbjerg, Jon Albretsen, Knud Simonsen, Erna Lava Olsen, Eigil Kaas, and Bogi Hansen
Ocean Sci., 17, 1639–1655, https://doi.org/10.5194/os-17-1639-2021, https://doi.org/10.5194/os-17-1639-2021, 2021
Short summary
Short summary
Here, we describe a strait that has narrow and shallow sills in both ends and is close to an amphidromic region. This generates tidally driven flows into and out of the strait, but with very different exchange rates across the entrances in both ends so that it behaves like a mixture between a strait and a fjord. Using a numerical model, we find a fortnightly signal in the net transport through the strait, generated by long-period tides. Our findings are verified by observations.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, Steingrímur Jónsson, Sólveig Rósa Ólafsdóttir, Andreas Macrander, William Johns, N. Penny Holliday, and Steffen Malskær Olsen
Ocean Sci. Discuss., https://doi.org/10.5194/os-2021-14, https://doi.org/10.5194/os-2021-14, 2021
Preprint withdrawn
Short summary
Short summary
Compared to other freshwater sources, runoff from Iceland is small and usually flows into the Nordic Seas. Under certain wind conditions, it can, however, flow into the Iceland Basin and this occurred after 2014, when this region had already freshened from other causes. This explains why the surface freshening in this area became so extreme. The local and shallow character of this runoff allows it to have a disproportionate effect on vertical mixing, winter convection, and biological production.
Svein Østerhus, Rebecca Woodgate, Héðinn Valdimarsson, Bill Turrell, Laura de Steur, Detlef Quadfasel, Steffen M. Olsen, Martin Moritz, Craig M. Lee, Karin Margretha H. Larsen, Steingrímur Jónsson, Clare Johnson, Kerstin Jochumsen, Bogi Hansen, Beth Curry, Stuart Cunningham, and Barbara Berx
Ocean Sci., 15, 379–399, https://doi.org/10.5194/os-15-379-2019, https://doi.org/10.5194/os-15-379-2019, 2019
Short summary
Short summary
Two decades of observations of the Arctic Mediterranean (AM) exchanges show that the exchanges have been stable in terms of volume transport during a period when many other components of the global climate system have changed. The total AM import is found to be 9.1 Sv and has a seasonal variation in amplitude close to 1 Sv, and maximum import in October. Roughly one-third of the imported water leaves the AM as surface outflow.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Steffen Malskær Olsen, Detlef Quadfasel, Kerstin Jochumsen, and Svein Østerhus
Ocean Sci., 14, 871–885, https://doi.org/10.5194/os-14-871-2018, https://doi.org/10.5194/os-14-871-2018, 2018
Short summary
Short summary
The Western Valley is one of the passages across the Iceland–Scotland Ridge through which a strong overflow of cold, dense water has been thought to feed the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), but its strength has not been known. Based on a field experiment with instruments moored across the valley, we show that this overflow branch is much weaker than previously thought and that this is because it is suppressed by the warm countercurrent in the upper layers.
Bogi Hansen, Turið Poulsen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, Svein Østerhus, Elin Darelius, Barbara Berx, Detlef Quadfasel, and Kerstin Jochumsen
Ocean Sci., 13, 873–888, https://doi.org/10.5194/os-13-873-2017, https://doi.org/10.5194/os-13-873-2017, 2017
Short summary
Short summary
On its way towards the Arctic, an important branch of warm Atlantic water passes through the Faroese Channels, but, in spite of more than a century of investigations, the detailed flow pattern through this channel system has not been resolved. This has strong implications for estimates of oceanic heat transport towards the Arctic. Here, we combine observations from various sources, which together paint a coherent picture of the Atlantic water flow and heat transport through this channel system.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, and Svein Østerhus
Ocean Sci., 12, 1205–1220, https://doi.org/10.5194/os-12-1205-2016, https://doi.org/10.5194/os-12-1205-2016, 2016
Short summary
Short summary
The Faroe Bank Channel is one of the main passages for the flow of cold dense water from the Arctic into the depths of the world ocean where it feeds the deep branch of the AMOC. Based on in situ measurements, we show that the volume transport of this flow has been stable from 1995 to 2015. The water has warmed, but salinity increase has maintained its high density. Thus, this branch of the AMOC did not weaken during the last 2 decades, but increased its heat transport into the deep ocean.
S. M. Olsen, B. Hansen, S. Østerhus, D. Quadfasel, and H. Valdimarsson
Ocean Sci., 12, 545–560, https://doi.org/10.5194/os-12-545-2016, https://doi.org/10.5194/os-12-545-2016, 2016
Short summary
Short summary
About half of the warm Atlantic water that enters the Norwegian Sea flows between Iceland and the Faroes. Here it crosses the Iceland-Faroe Ridge and dynamically interacts with the cold, dense and deep return flow across the ridge. This flow is not resolved in climate models and the lack of interaction prevents realistic heat anomaly propagation towards the Arctic.
E. Darelius, I. Fer, T. Rasmussen, C. Guo, and K. M. H. Larsen
Ocean Sci., 11, 855–871, https://doi.org/10.5194/os-11-855-2015, https://doi.org/10.5194/os-11-855-2015, 2015
Short summary
Short summary
Quasi-regular eddies are known to be generated in the outflow of dense water through the Faroe Bank Channel. One year long mooring records from the plume region show that (1) the energy associated with the eddies varies by a factor of 10 throughout the year and (2) the frequency of the eddies shifts between 3 and 6 days and is related to the strength of the outflow. Similar variability is shown by a high-resolution regional model and the observations agree with theory on baroclinic instability.
A. S. A. Ferreira, H. Hátún, F. Counillon, M. R. Payne, and A. W. Visser
Biogeosciences, 12, 3641–3653, https://doi.org/10.5194/bg-12-3641-2015, https://doi.org/10.5194/bg-12-3641-2015, 2015
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Our main objective was to assess which bottom-up processes can best predict changes in phytoplankton surface spring blooms in the North Atlantic. We applied new phenology algorithms to satellite-derived data and compared four different metrics based on physical drivers of phytoplankton. We show that there is a dominant physical mechanism - mixed layer shoaling - and that different regions are governed by different physical phenomena.
B. Berx, B. Hansen, S. Østerhus, K. M. Larsen, T. Sherwin, and K. Jochumsen
Ocean Sci., 9, 639–654, https://doi.org/10.5194/os-9-639-2013, https://doi.org/10.5194/os-9-639-2013, 2013
Related subject area
Approach: In situ Observations | Depth range: All Depths | Geographical range: Nordic Seas | Phenomena: Current Field
Norwegian Atlantic Slope Current along the Lofoten Escarpment
Does the East Greenland Current exist in the northern Fram Strait?
Overflow of cold water across the Iceland–Faroe Ridge through the Western Valley
Volume transport and mixing of the Faroe Bank Channel overflow from one year of moored measurements
On the modulation of the periodicity of the Faroe Bank Channel overflow instabilities
Combining in situ measurements and altimetry to estimate volume, heat and salt transport variability through the Faroe–Shetland Channel
A quantitative description of the Norwegian Atlantic Current by combining altimetry and hydrography
Ilker Fer, Anthony Bosse, and Johannes Dugstad
Ocean Sci., 16, 685–701, https://doi.org/10.5194/os-16-685-2020, https://doi.org/10.5194/os-16-685-2020, 2020
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We analyzed 14-month-long observations from moored instruments to describe the average features and the variability of the Norwegian Atlantic Slope Current at the Lofoten Escarpment (13°E, 69°N). The slope current varies strongly with depth and in time. Pulses of strong current occur, lasting for 1 to 2 weeks, and extend as deep as 600 m. The average volume transport is 2 x 106 m3 s-1.
Maren Elisabeth Richter, Wilken-Jon von Appen, and Claudia Wekerle
Ocean Sci., 14, 1147–1165, https://doi.org/10.5194/os-14-1147-2018, https://doi.org/10.5194/os-14-1147-2018, 2018
Short summary
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In the Fram Strait, Arctic Ocean outflow is joined by Atlantic Water (AW) that has not flowed through the Arctic Ocean. The confluence creates a density gradient which steepens and draws closer to the east Greenland shelf break from N to S. This brings the warm AW closer to the shelf break. South of 79° N, AW has reached the shelf break and the East Greenland Current has formed. When AW reaches the Greenland shelf it may propagate through troughs to glacier termini and contribute to glacier melt.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Steffen Malskær Olsen, Detlef Quadfasel, Kerstin Jochumsen, and Svein Østerhus
Ocean Sci., 14, 871–885, https://doi.org/10.5194/os-14-871-2018, https://doi.org/10.5194/os-14-871-2018, 2018
Short summary
Short summary
The Western Valley is one of the passages across the Iceland–Scotland Ridge through which a strong overflow of cold, dense water has been thought to feed the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), but its strength has not been known. Based on a field experiment with instruments moored across the valley, we show that this overflow branch is much weaker than previously thought and that this is because it is suppressed by the warm countercurrent in the upper layers.
Jenny E. Ullgren, Elin Darelius, and Ilker Fer
Ocean Sci., 12, 451–470, https://doi.org/10.5194/os-12-451-2016, https://doi.org/10.5194/os-12-451-2016, 2016
Short summary
Short summary
One-year long moored measurements of currents and hydrographic properties in the overflow region of the Faroe Bank Channel have provided a more accurate observational-based estimate of the volume transport, entrainment, and eddy diffusivities associated with the overflow plume. The data set resolves the temporal variability and covers the entire lateral and vertical extent of the plume.
E. Darelius, I. Fer, T. Rasmussen, C. Guo, and K. M. H. Larsen
Ocean Sci., 11, 855–871, https://doi.org/10.5194/os-11-855-2015, https://doi.org/10.5194/os-11-855-2015, 2015
Short summary
Short summary
Quasi-regular eddies are known to be generated in the outflow of dense water through the Faroe Bank Channel. One year long mooring records from the plume region show that (1) the energy associated with the eddies varies by a factor of 10 throughout the year and (2) the frequency of the eddies shifts between 3 and 6 days and is related to the strength of the outflow. Similar variability is shown by a high-resolution regional model and the observations agree with theory on baroclinic instability.
B. Berx, B. Hansen, S. Østerhus, K. M. Larsen, T. Sherwin, and K. Jochumsen
Ocean Sci., 9, 639–654, https://doi.org/10.5194/os-9-639-2013, https://doi.org/10.5194/os-9-639-2013, 2013
K. A. Mork and Ø. Skagseth
Ocean Sci., 6, 901–911, https://doi.org/10.5194/os-6-901-2010, https://doi.org/10.5194/os-6-901-2010, 2010
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Short summary
The Faroe Current is the main ocean current transporting warm Atlantic water into the Arctic region and an important transporter of heat towards the Arctic. This study documents observed transport variations over two decades, from 1993 to 2013. It shows that the volume transport of Atlantic water in this current increased by 9% over the period, whereas the heat transport increased by 18%. This increase will have contributed to the observed warming and sea ice decline in the Arctic.
The Faroe Current is the main ocean current transporting warm Atlantic water into the Arctic...