Alexander Korablev - Academia.edu (original) (raw)

Papers by Alexander Korablev

This NCEI accession consists of seawater Mg/Ca and Sr/Ca ratios, temperature, salinity, total alk... more This NCEI accession consists of seawater Mg/Ca and Sr/Ca ratios, temperature, salinity, total alkalinity, DIC and DO measured from 79 cruises between 2009 and 2017. The long debate about the conservative behaviour of seawater Mg/Ca and Sr/Ca ratios becomes more complex by studying the ocean as a whole and not only open ocean settings or the deep sea. In this project we measured in 79 cruises around the world seawater Mg/Ca and Sr/Ca ratios to discover that the modern ocean ranges are well beyond the pre-assumed values used by modellers, paleoceanographers and experimentalists as the basis for their work (Mg/Ca = 4.5 to 6.5 mol:mol and Sr/CA = 7 to 9.8 mmol:mol). We find out that modern seawater ranges are similar to the last 20 million years (Neogene) increase in these ratios, challenging the pre-assumed knowledge and a good number of methods used that assume a constant seawater Mg/Ca or Sr/Ca ratio. We agree that open ocean, the deep sea and reconstructions of past seawater based o...

The dynamic height D, defined as the product of the depth difference between two surfaces of cons... more The dynamic height D, defined as the product of the depth difference between two surfaces of constant pressure and gravity, is used for estimation of the ocean circulation at both regional and global scales. The dynamic height can be readily derived from 3-dimensional observations of temperature and salinity (i.e., from hydrography), or from Ocean General Circulation Models (OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's geoid. In this study, which is a part of the OCTAS project supported by the Research Council of Norway, and the GOCINA project supported by the EU, a unique Russian data set with about 127.000 hydrographic observations covering the 20 th century has been used to compute the mean value and the decadal variability of D of the Northeast Atlantic and Nordic Seas (Norwegian Sea, Greenland Sea and Barents Sea). Similar computations are made from an ocean general circulation model (OGCM) driven by daily NCEP atmospheric forcing f...

IOP Conference Series: Earth and Environmental Science, 2010

Geophysical Monograph Series, 2013

Eos, Transactions American Geophysical Union, 2012

Over the past 2 decades, large outlet glaciers in western and southeastern Greenland have acceler... more Over the past 2 decades, large outlet glaciers in western and southeastern Greenland have accelerated, thinned, and retreated [Rignot and Kanagaratnam, 2006; Howat et al., 2007], leading to a doubling of Greenland's contribution to sea level rise. Scientists believe that these changes were driven partly by increased submarine melting at the front of these glaciers in Greenland's deep fjords [Holland et al., 2008; Murray et al., 2010] due to increased inflow of warm subtropical waters from the Atlantic Ocean [Straneo et al., 2010; Motyka et al., 2011]. Improved understanding of the circulation within these fjords is important because their response to regional atmospheric, oceanic, and glacier variability is crucial to understanding the past and forecasting the future behavior of the glaciers. One major obstacle to progress in this area, however, is the lack of bathymetric data for the fjords.

Surveys in Geophysics, 2011

Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming c... more Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming can cause large changes in the outlet glaciers in these fjords. We have observed the Helheim outlet-glacier front in the Sermilik Fjord over the last three decades using satellite images, and the vertical fjord temperature and salinity during three summer expeditions, 2008-2010. We show that the subsurface water below 250 m depth is the warm saline Atlantic Water from the Irminger Sea penetrating into the fjord and exposing the lower part of the Helheim glacier to warm water up to 4°C. Lagged correlation analysis spanning the 30-year time series, using the subsurface Atlantic Water temperature off the coast as a proxy for the variability of the subsurface warm Atlantic Water in the fjord, indicates that 24% of the Helheim ice-front movement can be accounted for by ocean temperature. A strong correlation (-0.75) between the ice-front position and the surface air temperature from a nearby meteorological station suggests that the higher air temperature causes melting and subsequent downward percolation of meltwater through crevasses leading to basal lubrication; the correlation accounts for 56% of the ice-front movement. The precise contribution of air temperature versus ocean temperature however, remains an open question, as more oceanographic and meteorological measurements are needed close to the glacier terminus.

Journal of Geophysical Research, 2007

The variability of steric height in the Nordic Seas is analyzed on seasonal, interannual, and dec... more The variability of steric height in the Nordic Seas is analyzed on seasonal, interannual, and decadal timescales using a comprehensive data set of temperature and salinity observations for the second half of the twentieth century. Results from a regional Ocean General Circulation Model (OGCM) are used to assess the reliability of the averaging and the temporal interpolation of the inhomogeneous distributed observation data. The annual cycle explains only a minor part of the monthly variability for most of the region. The analysis on interannual to decadal timescales confined to the Norwegian Sea displays a clear rising trend starting at the end of the 1960s with particularly strong changes along the Barents Sea opening (6 to 7 cm). Moreover, a general freshening is found for the entire Norwegian Sea. In addition, a north-south dipole of the thermal component of the steric height variability is identified. This dipole elevates the general rising trend along the Barents Sea opening and reduces it in the southern Norwegian Sea. The bulk of the interannual variability in steric height is governed by variations in the local meridional wind stress that determine the relative distribution of Atlantic and Arctic waters in the Norwegian Sea. In addition, reduced heat loss to the atmosphere strongly correlates with the North Atlantic Oscillation winter index. This, in turn, may in particular explain the large steric height increase found at the Barents Sea opening.

Journal of Geophysical Research: Oceans, 2002

In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nord... more In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nordic Seas is investigated. The data include a Russian hydrographical database for the Nordic Seas and daily to weekly observations of salinity at Ocean Weather Station Mike (OWSM) (located at 66°N, 2°E in the Norwegian Sea). In addition, output from a mediumresolution version of the Miami Isopycnic Coordinate Ocean Model (MICOM), forced with daily National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, is used to complement the analysis of the temporal and spatial fields constructed from the observational data sets. The Nordic Seas show a strong seasonal variability in the vertical density stratification and the mixed layer (ML) depth, with a weak stratification and a several hundred meters deep ML during winter and a well-defined shallow ML confined to the upper few tens of meters during summer. The seasonal variability strongly influences the strength of the high-frequency variability and to what extent subsurface anomalies are isolated from the surface. Highfrequency variability has been investigated in terms of standard deviation of daily SSS, calculated for the different months of the year. From observations at OWSM, typical winter values range from 0.03 to 0.04 psu and summer values range from 0.06 to 0.07 psu. Results from the model simulation show that highest variability is found in frontal areas and in areas with strong stratification and lowest variability in the less stratified areas in the central Norwegian Sea and south of Iceland. Investigation of the interannual variability over the last 50 years shows a marked freshening of the Atlantic Water in the Norwegian and Greenland Seas. Moreover, the strength of the southern sector of the Polar front, as defined by the 34.8-35.0 psu isohalines along the western boundary of the inflowing Atlantic Water, undergoes significant interannual variability with gradient stretching reaching up to 300 km. In comparison, the variability in the strength of the eastern front and northern sector of the Polar front, seemingly controlled by the shelf break off Norway and the ridge between the Norwegian and the Greenland Seas, typically undergoes stretching only between 60 and 80 km. The investigation also demonstrates that the low-frequency variability in the upper ocean density field in the Greenland Sea, a key factor for the deep water convection, is governed by the variability in the sea surface field. Since the early 1960s, there has been a negative trend in the salinity, probably contributing to the observed decrease in the deep water production in that period.

Data Science Journal, 2013

We document the geographical and temporal distributions of oceanographic vertical profile observa... more We document the geographical and temporal distributions of oceanographic vertical profile observations made during World War II (1939-1945) that are included in the "World Ocean Database" (WOD). The WOD is a product of the NOAA/National Oceanographic Data Center, USA and its co-located ICSU World Data Center for Oceanography. The WOD is the largest collection of ocean profile data available internationally without restriction. All data shown in this paper are available online without restriction and at no cost. The WOD is built upon the international exchange of oceanographic data with contributions of data received from many countries. Most of the data shown in this paper and the data within the WOD in which these data reside in a uniform format were gathered under the auspices of the International Oceanographic Data and Information Exchange (IODE) committee of the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the ICSU (International Council of Science)

earth.esa.int

The dynamic height D, defined as the product of the depth difference between two surfaces of cons... more The dynamic height D, defined as the product of the depth difference between two surfaces of constant pressure and gravity, is used for estimation of the ocean circulation at both regional and global scales. The dynamic height can be readily derived from 3-dimensional observations of temperature and salinity (i.e., from hydrography), or from Ocean General Circulation Models (OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's geoid. In this study, which is a part of the OCTAS project supported by the Research Council of Norway, and the GOCINA project supported by the EU, a unique Russian data set with about 127.000 hydrographic observations covering the 20 th century has been used to compute the mean value and the decadal variability of D of the Northeast Atlantic and Nordic Seas (Norwegian Sea, Greenland Sea and Barents Sea). Similar computations are made from an ocean general circulation model (OGCM) driven by daily NCEP atmospheric forcing fields from the period 1948 to present. Analyses of the observed and simulated D-fields show fairly good temporal and spatial similarities. It is particularly evident that D varies on decadal time scales. Moreover the degree of variability in the region over the last 50 years is quantified. This quantification is of importance as it provides bounds on the accuracy required by remotely sensed sea surface height and the Earth's geoid fields for reliable estimates of the ocean circulation.

General for Maritime Affairs and Fisheries. *monthly fields were only computed if more than 3 sam... more General for Maritime Affairs and Fisheries. *monthly fields were only computed if more than 3 samples existed at a depth level; **numbers are different because not all years have data; ***number of maps is less than number of fields with data due a specific plotting software problem at deep depth levels when a variable has identical values at all locations; Vvariable (temperature, salinity or density); Ycalendar year; Mcalendar month; Lstandard depth level; Ptime period (anomalous or decadal);

Proceedings of the National Academy of Sciences

Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphe... more Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphere dynamic exchange of elements. The ratios’ dependence on the environment and organisms' biology facilitates their application in marine sciences. Here, we present a measured single-laboratory dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater Mg:Ca and Sr:Ca ratios range from ∼4.40 to 6.40 mmol:mol and ∼6.95 to 9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semiconservative (∼4.90 to 5.30 mol:mol), while Sr:Ca is more variable and nonconservative (∼7.70 to 8.80 mmol:mol); both ratios are nonconservative in coastal seas. Further, the Ca, Mg, and Sr elemental fluxes are connected to large total alkalinity deviations from International Association for th...

The goal of the Atlas is to provide the international scientific community and wider general publ... more The goal of the Atlas is to provide the international scientific community and wider general public with a regional dataset and illustrative material in support of climate change studies in the key regions of high northern latitudes. The dataset is built on an enhanced collection of observations spanning over a period from the end of the 19th century to 2012. It is based on in situ data that had

Journal of Geophysical Research, 2007

This NCEI accession consists of seawater Mg/Ca and Sr/Ca ratios, temperature, salinity, total alk... more This NCEI accession consists of seawater Mg/Ca and Sr/Ca ratios, temperature, salinity, total alkalinity, DIC and DO measured from 79 cruises between 2009 and 2017. The long debate about the conservative behaviour of seawater Mg/Ca and Sr/Ca ratios becomes more complex by studying the ocean as a whole and not only open ocean settings or the deep sea. In this project we measured in 79 cruises around the world seawater Mg/Ca and Sr/Ca ratios to discover that the modern ocean ranges are well beyond the pre-assumed values used by modellers, paleoceanographers and experimentalists as the basis for their work (Mg/Ca = 4.5 to 6.5 mol:mol and Sr/CA = 7 to 9.8 mmol:mol). We find out that modern seawater ranges are similar to the last 20 million years (Neogene) increase in these ratios, challenging the pre-assumed knowledge and a good number of methods used that assume a constant seawater Mg/Ca or Sr/Ca ratio. We agree that open ocean, the deep sea and reconstructions of past seawater based o...

The dynamic height D, defined as the product of the depth difference between two surfaces of cons... more The dynamic height D, defined as the product of the depth difference between two surfaces of constant pressure and gravity, is used for estimation of the ocean circulation at both regional and global scales. The dynamic height can be readily derived from 3-dimensional observations of temperature and salinity (i.e., from hydrography), or from Ocean General Circulation Models (OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's geoid. In this study, which is a part of the OCTAS project supported by the Research Council of Norway, and the GOCINA project supported by the EU, a unique Russian data set with about 127.000 hydrographic observations covering the 20 th century has been used to compute the mean value and the decadal variability of D of the Northeast Atlantic and Nordic Seas (Norwegian Sea, Greenland Sea and Barents Sea). Similar computations are made from an ocean general circulation model (OGCM) driven by daily NCEP atmospheric forcing f...

IOP Conference Series: Earth and Environmental Science, 2010

Geophysical Monograph Series, 2013

Eos, Transactions American Geophysical Union, 2012

Over the past 2 decades, large outlet glaciers in western and southeastern Greenland have acceler... more Over the past 2 decades, large outlet glaciers in western and southeastern Greenland have accelerated, thinned, and retreated [Rignot and Kanagaratnam, 2006; Howat et al., 2007], leading to a doubling of Greenland's contribution to sea level rise. Scientists believe that these changes were driven partly by increased submarine melting at the front of these glaciers in Greenland's deep fjords [Holland et al., 2008; Murray et al., 2010] due to increased inflow of warm subtropical waters from the Atlantic Ocean [Straneo et al., 2010; Motyka et al., 2011]. Improved understanding of the circulation within these fjords is important because their response to regional atmospheric, oceanic, and glacier variability is crucial to understanding the past and forecasting the future behavior of the glaciers. One major obstacle to progress in this area, however, is the lack of bathymetric data for the fjords.

Surveys in Geophysics, 2011

Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming c... more Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming can cause large changes in the outlet glaciers in these fjords. We have observed the Helheim outlet-glacier front in the Sermilik Fjord over the last three decades using satellite images, and the vertical fjord temperature and salinity during three summer expeditions, 2008-2010. We show that the subsurface water below 250 m depth is the warm saline Atlantic Water from the Irminger Sea penetrating into the fjord and exposing the lower part of the Helheim glacier to warm water up to 4°C. Lagged correlation analysis spanning the 30-year time series, using the subsurface Atlantic Water temperature off the coast as a proxy for the variability of the subsurface warm Atlantic Water in the fjord, indicates that 24% of the Helheim ice-front movement can be accounted for by ocean temperature. A strong correlation (-0.75) between the ice-front position and the surface air temperature from a nearby meteorological station suggests that the higher air temperature causes melting and subsequent downward percolation of meltwater through crevasses leading to basal lubrication; the correlation accounts for 56% of the ice-front movement. The precise contribution of air temperature versus ocean temperature however, remains an open question, as more oceanographic and meteorological measurements are needed close to the glacier terminus.

Journal of Geophysical Research, 2007

The variability of steric height in the Nordic Seas is analyzed on seasonal, interannual, and dec... more The variability of steric height in the Nordic Seas is analyzed on seasonal, interannual, and decadal timescales using a comprehensive data set of temperature and salinity observations for the second half of the twentieth century. Results from a regional Ocean General Circulation Model (OGCM) are used to assess the reliability of the averaging and the temporal interpolation of the inhomogeneous distributed observation data. The annual cycle explains only a minor part of the monthly variability for most of the region. The analysis on interannual to decadal timescales confined to the Norwegian Sea displays a clear rising trend starting at the end of the 1960s with particularly strong changes along the Barents Sea opening (6 to 7 cm). Moreover, a general freshening is found for the entire Norwegian Sea. In addition, a north-south dipole of the thermal component of the steric height variability is identified. This dipole elevates the general rising trend along the Barents Sea opening and reduces it in the southern Norwegian Sea. The bulk of the interannual variability in steric height is governed by variations in the local meridional wind stress that determine the relative distribution of Atlantic and Arctic waters in the Norwegian Sea. In addition, reduced heat loss to the atmosphere strongly correlates with the North Atlantic Oscillation winter index. This, in turn, may in particular explain the large steric height increase found at the Barents Sea opening.

Journal of Geophysical Research: Oceans, 2002

In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nord... more In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nordic Seas is investigated. The data include a Russian hydrographical database for the Nordic Seas and daily to weekly observations of salinity at Ocean Weather Station Mike (OWSM) (located at 66°N, 2°E in the Norwegian Sea). In addition, output from a mediumresolution version of the Miami Isopycnic Coordinate Ocean Model (MICOM), forced with daily National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, is used to complement the analysis of the temporal and spatial fields constructed from the observational data sets. The Nordic Seas show a strong seasonal variability in the vertical density stratification and the mixed layer (ML) depth, with a weak stratification and a several hundred meters deep ML during winter and a well-defined shallow ML confined to the upper few tens of meters during summer. The seasonal variability strongly influences the strength of the high-frequency variability and to what extent subsurface anomalies are isolated from the surface. Highfrequency variability has been investigated in terms of standard deviation of daily SSS, calculated for the different months of the year. From observations at OWSM, typical winter values range from 0.03 to 0.04 psu and summer values range from 0.06 to 0.07 psu. Results from the model simulation show that highest variability is found in frontal areas and in areas with strong stratification and lowest variability in the less stratified areas in the central Norwegian Sea and south of Iceland. Investigation of the interannual variability over the last 50 years shows a marked freshening of the Atlantic Water in the Norwegian and Greenland Seas. Moreover, the strength of the southern sector of the Polar front, as defined by the 34.8-35.0 psu isohalines along the western boundary of the inflowing Atlantic Water, undergoes significant interannual variability with gradient stretching reaching up to 300 km. In comparison, the variability in the strength of the eastern front and northern sector of the Polar front, seemingly controlled by the shelf break off Norway and the ridge between the Norwegian and the Greenland Seas, typically undergoes stretching only between 60 and 80 km. The investigation also demonstrates that the low-frequency variability in the upper ocean density field in the Greenland Sea, a key factor for the deep water convection, is governed by the variability in the sea surface field. Since the early 1960s, there has been a negative trend in the salinity, probably contributing to the observed decrease in the deep water production in that period.

Data Science Journal, 2013

We document the geographical and temporal distributions of oceanographic vertical profile observa... more We document the geographical and temporal distributions of oceanographic vertical profile observations made during World War II (1939-1945) that are included in the "World Ocean Database" (WOD). The WOD is a product of the NOAA/National Oceanographic Data Center, USA and its co-located ICSU World Data Center for Oceanography. The WOD is the largest collection of ocean profile data available internationally without restriction. All data shown in this paper are available online without restriction and at no cost. The WOD is built upon the international exchange of oceanographic data with contributions of data received from many countries. Most of the data shown in this paper and the data within the WOD in which these data reside in a uniform format were gathered under the auspices of the International Oceanographic Data and Information Exchange (IODE) committee of the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the ICSU (International Council of Science)

earth.esa.int

The dynamic height D, defined as the product of the depth difference between two surfaces of cons... more The dynamic height D, defined as the product of the depth difference between two surfaces of constant pressure and gravity, is used for estimation of the ocean circulation at both regional and global scales. The dynamic height can be readily derived from 3-dimensional observations of temperature and salinity (i.e., from hydrography), or from Ocean General Circulation Models (OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's geoid. In this study, which is a part of the OCTAS project supported by the Research Council of Norway, and the GOCINA project supported by the EU, a unique Russian data set with about 127.000 hydrographic observations covering the 20 th century has been used to compute the mean value and the decadal variability of D of the Northeast Atlantic and Nordic Seas (Norwegian Sea, Greenland Sea and Barents Sea). Similar computations are made from an ocean general circulation model (OGCM) driven by daily NCEP atmospheric forcing fields from the period 1948 to present. Analyses of the observed and simulated D-fields show fairly good temporal and spatial similarities. It is particularly evident that D varies on decadal time scales. Moreover the degree of variability in the region over the last 50 years is quantified. This quantification is of importance as it provides bounds on the accuracy required by remotely sensed sea surface height and the Earth's geoid fields for reliable estimates of the ocean circulation.

General for Maritime Affairs and Fisheries. *monthly fields were only computed if more than 3 sam... more General for Maritime Affairs and Fisheries. *monthly fields were only computed if more than 3 samples existed at a depth level; **numbers are different because not all years have data; ***number of maps is less than number of fields with data due a specific plotting software problem at deep depth levels when a variable has identical values at all locations; Vvariable (temperature, salinity or density); Ycalendar year; Mcalendar month; Lstandard depth level; Ptime period (anomalous or decadal);

Proceedings of the National Academy of Sciences

Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphe... more Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphere dynamic exchange of elements. The ratios’ dependence on the environment and organisms' biology facilitates their application in marine sciences. Here, we present a measured single-laboratory dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater Mg:Ca and Sr:Ca ratios range from ∼4.40 to 6.40 mmol:mol and ∼6.95 to 9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semiconservative (∼4.90 to 5.30 mol:mol), while Sr:Ca is more variable and nonconservative (∼7.70 to 8.80 mmol:mol); both ratios are nonconservative in coastal seas. Further, the Ca, Mg, and Sr elemental fluxes are connected to large total alkalinity deviations from International Association for th...

The goal of the Atlas is to provide the international scientific community and wider general publ... more The goal of the Atlas is to provide the international scientific community and wider general public with a regional dataset and illustrative material in support of climate change studies in the key regions of high northern latitudes. The dataset is built on an enhanced collection of observations spanning over a period from the end of the 19th century to 2012. It is based on in situ data that had

Journal of Geophysical Research, 2007