Terje Brinck Løyning | Narvik University College (original) (raw)

Papers by Terje Brinck Løyning

Polar Research, Dec 1, 1991

This study is part of the Soviet-Norwegian Oceanographic Programme (SNOP) on ice and water dynami... more This study is part of the Soviet-Norwegian Oceanographic Programme (SNOP) on ice and water dynamics in the region between Svalbard and Frans Josef Land. The effects of the movements of water and ice on the ice regime are discussed. Due to the scarcity of data, numerical hydrodynamical simulations are used. The tidal ice drift is visualized on satellite images as elliptically shaped traces in the ice fields formed by grounded icebergs. These traces are a result of the joint action of tides. wind and permanent currents.

As described by several authors the last century, the source of heat and salt to the Barents Sea

Totally 36 icebergs were observed during the survey in the area between Hopen and Kong Karls Land... more Totally 36 icebergs were observed during the survey in the area between Hopen and Kong Karls Land. The majority of these icebergs were small and trapped in the landfast ice at Kong Karls Land. 4 Argos buoys were deployed, two on floating icebergs and two on grounded ones . The ice conditions were characterized by thin to medium first year ice. The amount of multi-year ice was negligible

This data collection contains physical oceanographic and hydrochemistry data from 82 cruises in t... more This data collection contains physical oceanographic and hydrochemistry data from 82 cruises in the frame of the project VEINS -Variability of Exchanges in the Northern Seas.

Analysis of CTD observations in the Greenland Sea Gyre (GSG) from various sources for the period ... more Analysis of CTD observations in the Greenland Sea Gyre (GSG) from various sources for the period 1950-2002 reveals new information and confirms old knowledge about the seasonal, inter-annual and decadal variations of the GSG hydrography. Analysis of extreme values confirms that the maximum temperatures can be found in August, and the minimum temperatures can be found in January-February. The temperature signal of maximum temperatures can be found at 50m depth in September, at 100m depth in November, and below 1000m in March-April. Seasonal variability of the salinity has an opposite structure with minimum in August and maximum in January-February. Our investigations, including recent cruises in 2001 and 2002, show that there is a continuous warming of the deep waters from 1990 until today. At 1500m the temperature has increased with 0.3 degree per decade since 1980. The warming is significant in all seasons. Analysis of the interdecadal variability of the geostrophic circulation sho...

Journal of Geophysical Research: Oceans, 2013

ABSTRACT Time series (1990-2011) of sea ice thickness observed by moored sonars in the Transpolar... more ABSTRACT Time series (1990-2011) of sea ice thickness observed by moored sonars in the Transpolar Drift in Fram Strait are examined. Contrasting the post 2007 years against the 1990s, three remarkable changes in the monthly ice thickness distributions are highlighted: 1) The thickness of old level ice (modal thickness) is reduced by 32 percent, 2) the old ice modal peak width is reduced by 25 percent, and 3) the fraction of (ridged) ice thicker than 5 m is reduced by 50 percent. The combined effect on the mean ice thickness is a reduction from an annual average of 3.0 m during the 1990s to 2.2 m during 2008-2011. Most of the thinning took place after 2005-2006. While the old ice modal thickness and peak width show signs of recovery after 2008, the decreasing trend in fraction of ridged ice and mean ice thickness persists until the end of the record in 2011. The ice observed in Fram Strait carries an integrated signal of Arctic change due to the advection of ice from many sites in the Arctic. Based on concurrence in timing, we conclude that much of the thinning quantified here is reflecting recent change in the age composition of the Arctic ice cover towards younger ice. The old level ice remains thin, and as such the ice cover remains preconditioned for new summers of very low sea ice extent.

An analysis of a hundred-year record (1898-1999) of monthly mean sea level atmospheric pressure (... more An analysis of a hundred-year record (1898-1999) of monthly mean sea level atmospheric pressure (SLP) on the northern hemisphere reveals new features of geographical distribution and variability. The results of this analysis show that the extreme low and high values of the monthly mean SLP on the northern hemisphere occurs in three narrow meridional bands, located in the Atlantic, the Pacific and over the Eurasian continent. We also find that the annually averaged extremes of SLP have been relocated in all three regions in the period between 1898-1999. The consequences of these relocations are that the distance between the latitudes of extreme low and extreme high values of SLP have decreased over the period in the Atlantic and Pacific regions, and became zero or close to zero in the 1990s. Over the Eurasian continent the difference was zero around 1920, and has become increasingly larger since then, with the extreme low values of the SLP at the northernmost positions. Based on thes...

Journal of Marine Systems, 2000

Geophysical Research Letters, 2004

The first convective chimney in the Greenland Sea to have its temperature and salinity structure ... more The first convective chimney in the Greenland Sea to have its temperature and salinity structure fully mapped was discovered in March 2001 near 75°N 0°W [Wadhams et al., 2002]. Later cruises have shown that this remarkable feature has survived for a further 26 months, being remapped in summer 2001, winter 2002, summer 2002 and most recently in April–May 2003, making it the longest-lived chimney yet seen in the world ocean. The chimney has an anticyclonically rotating core and experiences an annual cycle in which it is uniform in properties from the surface to 2500 m in winter, but is capped by lower-density water in summer. The latest cruise also discovered a second chimney, 70 km NW of the first, during a thorough survey of 15,000 km2 of the gyre centre which left the existence of further chimneys unlikely. We conclude that the 75°/0° chimney is not unique, but that Greenland Sea chimneys are rare and are probably rarer than in 1997, when several such features were discovered by a float survey. This has implications for deep water renewal and for the role of Greenland Sea convection in the North Atlantic circulation.

Geophysical Research Letters, 2008

Seasonal fast ice thickness at the island of Hopen (Barents Sea) was monitored over 40 years. Sea... more Seasonal fast ice thickness at the island of Hopen (Barents Sea) was monitored over 40 years. Sea ice thickness variability as a climate indicator provides more quantitative information on the state of the ice cover than solely sea ice extent. Usually, starting to form just before December Hopen fast ice reaches maximum thickness in May (on average 0.99 m), before

Tellus A, 2006

A theoretical investigation shows that the pressure dependence of the thermal expansion coefficie... more A theoretical investigation shows that the pressure dependence of the thermal expansion coefficient (the thermobaric effect) acts to destabilize stratified geostrophic flows when both temperature and salinity contribute positively to the vertical stability. For vertical stability where the salinity contributes negatively, the thermobaric effect may act to stabilize the flow. The considered disturbances are small-amplitude two-dimensional rolls with axes aligned along the basic geostrophic current, and the growth mechanism is symmetric baroclinic instability. The boundaries of the marginally stable convection cells are essentially parallel to the slanting isopycnals of the basic state; therefore, the term slantwise convection is used to describe this phenomenon. Furthermore, the thermobaric effect induces a shift of the centres of the convection cells towards the lower part of the fluid layer, as previously demonstrated for buoyancy-driven convection. The width of the marginally stable cells is small and determined by turbulent diffusion processes in the fluid.

Journal of Geophysical Research, 1997

The equations governing buoyancy-driven convection in a rotating horizontal fluid layer, where th... more The equations governing buoyancy-driven convection in a rotating horizontal fluid layer, where the thermal expansion coefficient is a function of pressure (here, depth), have been derived. The results confirm the validity of the Boussinesq approximation. Furthermore, the adiabatic lapse rate for cold seawater is shown to be so small that it can usually be neglected in comparison to the in situ temperature gradient. For purely thermal convection a linear perturbation analysis shows that a weak thermobaric effect acts as a destabilizing influence on the Rayleigh-B•nard problem. This is also the case when Earth's rotation is taken into account. In particular, for marginal stability in the absence of rotation, it is shown that two-dimensional convection cells are asymmetric with respect to the midlayer plane, with stronger circulation in the deeper part of the layer. This effect is also revealed by two-dimensional, nonlinear numerical computations, when the layer is stratified by opposing gradients of heat (acting destabilizing) and salt (acting stabilizing). For thermobaric convection, i.e., in cases where the layer would have been stable in the absence of the thermobaric effect, the computed cell pattern is seen to be displaced toward the deeper part of the layer. Furthermore, the cell width increases with increasing thermobaric strength. It is suggested that thermobaric convection may act in conjunction with haline convection due to freezing in the process of vertical mixing and deep water formation in polar areas. tails. Gill [1973] recognized the dynamic significance of the variation of the thermal expansion coefficient with pressure, or

Geophysical Research Letters, 2002

Ice thickness and drift measurements complemented with modeling results are examined. In the East... more Ice thickness and drift measurements complemented with modeling results are examined. In the East-Greenland ice drift stream (EGIS), the ice is thicker at 79°N than at 75°N in winter but similar in summer due to melting, advection, and seasonal changes of the wind pattern in Fram Strait. Ice fluxes at 79°N and 75°N vary coherently. Summer EGIS melting rates exceed

National Institute Polar Research Memoirs, Jan 6, 2001

Geophysical Research Letters, 2004

The first convective chimney in the Greenland Sea to have its temperature and salinity structure ... more The first convective chimney in the Greenland Sea to have its temperature and salinity structure fully mapped was discovered in March 2001 near 75°N 0°W [Wadhams et al., 2002]. Later cruises have shown that this remarkable feature has survived for a further 26 months, being remapped in summer 2001, winter 2002, summer 2002 and most recently in April–May 2003, making it the longest-lived chimney yet seen in the world ocean. The chimney has an anticyclonically rotating core and experiences an annual cycle in which it is uniform in properties from the surface to 2500 m in winter, but is capped by lower-density water in summer. The latest cruise also discovered a second chimney, 70 km NW of the first, during a thorough survey of 15,000 km2 of the gyre centre which left the existence of further chimneys unlikely. We conclude that the 75°/0° chimney is not unique, but that Greenland Sea chimneys are rare and are probably rarer than in 1997, when several such features were discovered by a float survey. This has implications for deep water renewal and for the role of Greenland Sea convection in the North Atlantic circulation.

Polar Research, Dec 1, 1991

This study is part of the Soviet-Norwegian Oceanographic Programme (SNOP) on ice and water dynami... more This study is part of the Soviet-Norwegian Oceanographic Programme (SNOP) on ice and water dynamics in the region between Svalbard and Frans Josef Land. The effects of the movements of water and ice on the ice regime are discussed. Due to the scarcity of data, numerical hydrodynamical simulations are used. The tidal ice drift is visualized on satellite images as elliptically shaped traces in the ice fields formed by grounded icebergs. These traces are a result of the joint action of tides. wind and permanent currents.

As described by several authors the last century, the source of heat and salt to the Barents Sea

Totally 36 icebergs were observed during the survey in the area between Hopen and Kong Karls Land... more Totally 36 icebergs were observed during the survey in the area between Hopen and Kong Karls Land. The majority of these icebergs were small and trapped in the landfast ice at Kong Karls Land. 4 Argos buoys were deployed, two on floating icebergs and two on grounded ones . The ice conditions were characterized by thin to medium first year ice. The amount of multi-year ice was negligible

This data collection contains physical oceanographic and hydrochemistry data from 82 cruises in t... more This data collection contains physical oceanographic and hydrochemistry data from 82 cruises in the frame of the project VEINS -Variability of Exchanges in the Northern Seas.

Analysis of CTD observations in the Greenland Sea Gyre (GSG) from various sources for the period ... more Analysis of CTD observations in the Greenland Sea Gyre (GSG) from various sources for the period 1950-2002 reveals new information and confirms old knowledge about the seasonal, inter-annual and decadal variations of the GSG hydrography. Analysis of extreme values confirms that the maximum temperatures can be found in August, and the minimum temperatures can be found in January-February. The temperature signal of maximum temperatures can be found at 50m depth in September, at 100m depth in November, and below 1000m in March-April. Seasonal variability of the salinity has an opposite structure with minimum in August and maximum in January-February. Our investigations, including recent cruises in 2001 and 2002, show that there is a continuous warming of the deep waters from 1990 until today. At 1500m the temperature has increased with 0.3 degree per decade since 1980. The warming is significant in all seasons. Analysis of the interdecadal variability of the geostrophic circulation sho...

Journal of Geophysical Research: Oceans, 2013

ABSTRACT Time series (1990-2011) of sea ice thickness observed by moored sonars in the Transpolar... more ABSTRACT Time series (1990-2011) of sea ice thickness observed by moored sonars in the Transpolar Drift in Fram Strait are examined. Contrasting the post 2007 years against the 1990s, three remarkable changes in the monthly ice thickness distributions are highlighted: 1) The thickness of old level ice (modal thickness) is reduced by 32 percent, 2) the old ice modal peak width is reduced by 25 percent, and 3) the fraction of (ridged) ice thicker than 5 m is reduced by 50 percent. The combined effect on the mean ice thickness is a reduction from an annual average of 3.0 m during the 1990s to 2.2 m during 2008-2011. Most of the thinning took place after 2005-2006. While the old ice modal thickness and peak width show signs of recovery after 2008, the decreasing trend in fraction of ridged ice and mean ice thickness persists until the end of the record in 2011. The ice observed in Fram Strait carries an integrated signal of Arctic change due to the advection of ice from many sites in the Arctic. Based on concurrence in timing, we conclude that much of the thinning quantified here is reflecting recent change in the age composition of the Arctic ice cover towards younger ice. The old level ice remains thin, and as such the ice cover remains preconditioned for new summers of very low sea ice extent.

An analysis of a hundred-year record (1898-1999) of monthly mean sea level atmospheric pressure (... more An analysis of a hundred-year record (1898-1999) of monthly mean sea level atmospheric pressure (SLP) on the northern hemisphere reveals new features of geographical distribution and variability. The results of this analysis show that the extreme low and high values of the monthly mean SLP on the northern hemisphere occurs in three narrow meridional bands, located in the Atlantic, the Pacific and over the Eurasian continent. We also find that the annually averaged extremes of SLP have been relocated in all three regions in the period between 1898-1999. The consequences of these relocations are that the distance between the latitudes of extreme low and extreme high values of SLP have decreased over the period in the Atlantic and Pacific regions, and became zero or close to zero in the 1990s. Over the Eurasian continent the difference was zero around 1920, and has become increasingly larger since then, with the extreme low values of the SLP at the northernmost positions. Based on thes...

Journal of Marine Systems, 2000

Geophysical Research Letters, 2004

The first convective chimney in the Greenland Sea to have its temperature and salinity structure ... more The first convective chimney in the Greenland Sea to have its temperature and salinity structure fully mapped was discovered in March 2001 near 75°N 0°W [Wadhams et al., 2002]. Later cruises have shown that this remarkable feature has survived for a further 26 months, being remapped in summer 2001, winter 2002, summer 2002 and most recently in April–May 2003, making it the longest-lived chimney yet seen in the world ocean. The chimney has an anticyclonically rotating core and experiences an annual cycle in which it is uniform in properties from the surface to 2500 m in winter, but is capped by lower-density water in summer. The latest cruise also discovered a second chimney, 70 km NW of the first, during a thorough survey of 15,000 km2 of the gyre centre which left the existence of further chimneys unlikely. We conclude that the 75°/0° chimney is not unique, but that Greenland Sea chimneys are rare and are probably rarer than in 1997, when several such features were discovered by a float survey. This has implications for deep water renewal and for the role of Greenland Sea convection in the North Atlantic circulation.

Geophysical Research Letters, 2008

Seasonal fast ice thickness at the island of Hopen (Barents Sea) was monitored over 40 years. Sea... more Seasonal fast ice thickness at the island of Hopen (Barents Sea) was monitored over 40 years. Sea ice thickness variability as a climate indicator provides more quantitative information on the state of the ice cover than solely sea ice extent. Usually, starting to form just before December Hopen fast ice reaches maximum thickness in May (on average 0.99 m), before

Tellus A, 2006

A theoretical investigation shows that the pressure dependence of the thermal expansion coefficie... more A theoretical investigation shows that the pressure dependence of the thermal expansion coefficient (the thermobaric effect) acts to destabilize stratified geostrophic flows when both temperature and salinity contribute positively to the vertical stability. For vertical stability where the salinity contributes negatively, the thermobaric effect may act to stabilize the flow. The considered disturbances are small-amplitude two-dimensional rolls with axes aligned along the basic geostrophic current, and the growth mechanism is symmetric baroclinic instability. The boundaries of the marginally stable convection cells are essentially parallel to the slanting isopycnals of the basic state; therefore, the term slantwise convection is used to describe this phenomenon. Furthermore, the thermobaric effect induces a shift of the centres of the convection cells towards the lower part of the fluid layer, as previously demonstrated for buoyancy-driven convection. The width of the marginally stable cells is small and determined by turbulent diffusion processes in the fluid.

Journal of Geophysical Research, 1997

The equations governing buoyancy-driven convection in a rotating horizontal fluid layer, where th... more The equations governing buoyancy-driven convection in a rotating horizontal fluid layer, where the thermal expansion coefficient is a function of pressure (here, depth), have been derived. The results confirm the validity of the Boussinesq approximation. Furthermore, the adiabatic lapse rate for cold seawater is shown to be so small that it can usually be neglected in comparison to the in situ temperature gradient. For purely thermal convection a linear perturbation analysis shows that a weak thermobaric effect acts as a destabilizing influence on the Rayleigh-B•nard problem. This is also the case when Earth's rotation is taken into account. In particular, for marginal stability in the absence of rotation, it is shown that two-dimensional convection cells are asymmetric with respect to the midlayer plane, with stronger circulation in the deeper part of the layer. This effect is also revealed by two-dimensional, nonlinear numerical computations, when the layer is stratified by opposing gradients of heat (acting destabilizing) and salt (acting stabilizing). For thermobaric convection, i.e., in cases where the layer would have been stable in the absence of the thermobaric effect, the computed cell pattern is seen to be displaced toward the deeper part of the layer. Furthermore, the cell width increases with increasing thermobaric strength. It is suggested that thermobaric convection may act in conjunction with haline convection due to freezing in the process of vertical mixing and deep water formation in polar areas. tails. Gill [1973] recognized the dynamic significance of the variation of the thermal expansion coefficient with pressure, or

Geophysical Research Letters, 2002

Ice thickness and drift measurements complemented with modeling results are examined. In the East... more Ice thickness and drift measurements complemented with modeling results are examined. In the East-Greenland ice drift stream (EGIS), the ice is thicker at 79°N than at 75°N in winter but similar in summer due to melting, advection, and seasonal changes of the wind pattern in Fram Strait. Ice fluxes at 79°N and 75°N vary coherently. Summer EGIS melting rates exceed

National Institute Polar Research Memoirs, Jan 6, 2001

Geophysical Research Letters, 2004

The first convective chimney in the Greenland Sea to have its temperature and salinity structure ... more The first convective chimney in the Greenland Sea to have its temperature and salinity structure fully mapped was discovered in March 2001 near 75°N 0°W [Wadhams et al., 2002]. Later cruises have shown that this remarkable feature has survived for a further 26 months, being remapped in summer 2001, winter 2002, summer 2002 and most recently in April–May 2003, making it the longest-lived chimney yet seen in the world ocean. The chimney has an anticyclonically rotating core and experiences an annual cycle in which it is uniform in properties from the surface to 2500 m in winter, but is capped by lower-density water in summer. The latest cruise also discovered a second chimney, 70 km NW of the first, during a thorough survey of 15,000 km2 of the gyre centre which left the existence of further chimneys unlikely. We conclude that the 75°/0° chimney is not unique, but that Greenland Sea chimneys are rare and are probably rarer than in 1997, when several such features were discovered by a float survey. This has implications for deep water renewal and for the role of Greenland Sea convection in the North Atlantic circulation.