scholarly journals Time and space variability of freshwater content, heat content and seasonal ice melt in the Arctic Ocean from 1991 to 2011

2012 ◽  
Vol 9 (4) ◽  
pp. 2621-2677 ◽  
Author(s):  
M. Korhonen ◽  
B. Rudels ◽  
M. Marnela ◽  
A. Wisotzki ◽  
J. Zhao
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Mixed Layer ◽  
Heat Content ◽  
The Arctic ◽  
Upper Ocean ◽  
Heat Sources ◽  
Time And Space ◽  
Ice Melt ◽  
The Arctic Ocean

Abstract. The Arctic Ocean gains freshwater mainly through river discharge, precipitation and the inflowing low salinity waters from the Pacific Ocean. In addition the recent reduction in sea ice volume is likely to influence the surface salinity and thus contribute to the freshwater content in the upper ocean. The present day freshwater storage in the Arctic Ocean appears to be sufficient to maintain the upper ocean stratification and to protect the sea ice from the deep ocean heat content. The recent freshening has not, despite the established strong stratification, been able to restrain the accelerating ice loss and other possible heat sources besides the Atlantic Water, such as the waters advecting from the Pacific Ocean and the solar insolation warming the Polar Mixed Layer, are investigated. Since the ongoing freshening, oceanic heat sources and the sea ice melt are closely related, this study, based on hydrographic observations, attempts to examine the ongoing variability in time and space in relation to these three properties. The largest time and space variability of freshwater content occurs in the Polar Mixed Layer and the upper halocline. The freshening of the upper ocean during the 2000s is ubiquitous in the Arctic Ocean although the most substantial increase occurs in the Canada Basin where the freshwater is accumulating in the thickening upper halocline. Whereas the salinity of the upper halocline is nearly constant, the freshwater content in the Polar Mixed Layer is increasing due to decreasing salinity. The decrease in salinity is likely to result from the recent changes in ice formation and melting. In contrast, in the Eurasian Basin where the seasonal ice melt has remained rather modest, the freshening of both the Polar Mixed Layer and the upper halocline is mainly of advective origin. While the warming of the Atlantic inflow was widespread in the Arctic Ocean during the 1990s, the warm and saline inflow events in the early 2000s appear to circulate mainly in the Nansen Basin. Nevertheless, even in the Nansen Basin the seasonal ice melt appears independent of the continuously increasing heat content in the Atlantic layer. As no other oceanic heat sources can be identified in the upper layers, it is likely that increased absorption of solar energy has been causing the ice melt prior to the observations.

scholarly journals The Impact of Arctic Winter Infrared Radiation on Early Summer Sea Ice

2015 ◽  
Vol 28 (15) ◽  
pp. 6281-6296 ◽  
Author(s):  
Hyo-Seok Park ◽  
Sukyoung Lee ◽  
Yu Kosaka ◽  
Seok-Woo Son ◽  
Sang-Woo Kim
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Interannual Variability ◽  
Radiative Forcing ◽  
Heat Content ◽  
The Arctic ◽  
Upper Ocean ◽  
Upper Ocean Heat Content ◽  
The Arctic Ocean ◽  
Arctic Summer

Abstract The Arctic summer sea ice area has been rapidly decreasing in recent decades. In addition to this trend, substantial interannual variability is present, as is highlighted by the recovery in sea ice area in 2013 following the record minimum in 2012. This interannual variability of the Arctic summer sea ice area has been attributed to the springtime weather disturbances. Here, by utilizing reanalysis- and satellite-based sea ice data, this study shows that summers with unusually small sea ice area are preceded by winters with anomalously strong downward longwave radiation over the Eurasian sector of the Arctic Ocean. This anomalous wintertime radiative forcing at the surface is up to 10–15 W m−2, which is about twice as strong than that during the spring. During the same winters, the poleward moisture and warm-air intrusions into the Eurasian sector of the Arctic Ocean are anomalously strong and the resulting moisture convergence field closely resembles positive anomalies in column-integrated water vapor and tropospheric temperature. Climate model simulations support the above-mentioned findings and further show that the anomalously strong wintertime radiative forcing can decrease sea ice thickness over wide areas of the Arctic Ocean, especially over the Eurasian sector. During the winters preceding the anomalously small summer sea ice area, the upper ocean of the model is anomalously warm over the Barents Sea, indicating that the upper-ocean heat content contributes to winter sea ice thinning. Finally, mass divergence by ice drift in the preceding winter and spring contributes to the thinning of sea ice over the East Siberian and Chukchi Seas, where radiative forcing and upper-ocean heat content anomalies are relatively weak.

scholarly journals Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer

2011 ◽  
Vol 8 (1) ◽  
pp. 247-289 ◽  
Author(s):  
A. Sirevaag ◽  
S. de la Rosa ◽  
I. Fer ◽  
M. Nicolaus ◽  
M. Tjernström ◽  
...  
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Arctic Ocean ◽  
Mixed Layer ◽  
Heat Content ◽  
The Arctic ◽  
Upper Ocean ◽  
Ocean Mixed Layer ◽  
The Arctic Ocean ◽  
Melting Season

Abstract. A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the Central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance of solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22% of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the pycnocline accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m−2) and heated by solar radiation through the ice (−2.6 W m−2). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59% in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.

scholarly journals Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer

Ocean Science ◽  
2011 ◽  
Vol 7 (3) ◽  
pp. 335-349 ◽  
Author(s):  
A. Sirevaag ◽  
S. de la Rosa ◽  
I. Fer ◽  
M. Nicolaus ◽  
M. Tjernström ◽  
...  
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Arctic Ocean ◽  
Mixed Layer ◽  
Heat Content ◽  
The Arctic ◽  
Upper Ocean ◽  
Ocean Mixed Layer ◽  
The Arctic Ocean ◽  
Melting Season

Abstract. A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22 % of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the base of the mixed layer accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m−2) and heated by solar radiation through the ice (−2.6 W m−2). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59 % in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.

scholarly journals Time and space variability of freshwater content, heat content and seasonal ice melt in the Arctic Ocean from 1991 to 2011

Ocean Science ◽  
2013 ◽  
Vol 9 (6) ◽  
pp. 1015-1055 ◽  
Author(s):  
M. Korhonen ◽  
B. Rudels ◽  
M. Marnela ◽  
A. Wisotzki ◽  
J. Zhao
Keyword(s):  
Arctic Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Atlantic Water ◽  
The Arctic ◽  
Upper Ocean ◽  
Science Center ◽  
Ice Melt ◽  
Space And Time ◽  
The Arctic Ocean

Abstract. Changes in the hydrography of the Arctic Ocean have recently been reported. The upper ocean has been freshening and pulses of warm Atlantic Water have been observed to spread into the Arctic Ocean. Although these changes have been intensively studied, salinity and temperature variations have less frequently been considered together. Here hydrographic observations, obtained by icebreaker expeditions conducted between 1991 and 2011, are analyzed and discussed. Five different water masses in the upper 1000 m of the water column are examined in five sub-basins of the Arctic Ocean. This allows for studying the variations of the distributions of the freshwater and heat contents in the Arctic Ocean not only in time but also laterally and vertically. In addition, the seasonal ice melt contribution is separated from the permanent, winter, freshwater content of the Polar Mixed Layer. Because the positions of the icebreaker stations vary between the years, the icebreaker observations are at each specific point in space and time compared with the Polar Science Center Hydrographic Climatology to separate the effects of space and time variability on the observations. The hydrographic melt water estimate is discussed and compared with the potential ice melt induced by atmospheric heat input estimated from the ERA–Interim and NCEP/NCAR reanalyses. After a period of increased salinity in the upper ocean during the 1990s, both the Polar Mixed Layer and the upper halocline have been freshening. The increase in freshwater content in the Polar Mixed Layer is primarily driven by a decrease in salinity, not by changes in Polar Mixed Layer depth, whereas the freshwater is accumulating in the upper halocline mainly through the increasing thickness of the halocline. This is especially evident in the Northern Canada Basin, where the most substantial freshening is observed. The warming, and to some extent also the increase in salinity, of the Atlantic Water during the early 1990s extended from the Nansen Basin into the Amundsen and Makarov basins, while the warm and saline inflows occurring during the 2000s appear to be confined to the Nansen Basin, suggesting that the warm and saline inflow through Fram Strait largely recirculates in the Nansen Basin.

scholarly journals Chytrid fungi distribution and co-occurrence with diatoms correlate with sea ice melt in the Arctic Ocean

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Estelle S. Kilias ◽  
Leandro Junges ◽  
Luka Šupraha ◽  
Guy Leonard ◽  
Katja Metfies ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
The Arctic ◽  
Ice Melt ◽  
The Arctic Ocean

Brine-Driven Eddies under Sea Ice Leads and Their Impact on the Arctic Ocean Mixed Layer

2008 ◽  
Vol 38 (1) ◽  
pp. 146-163 ◽  
Author(s):  
Yoshimasa Matsumura ◽  
Hiroyasu Hasumi
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Mixed Layer ◽  
General Circulation ◽  
Salt Transport ◽  
Salt Flux ◽  
The Arctic ◽  
Theoretical Argument ◽  
Ocean Mixed Layer ◽  
The Arctic Ocean

Abstract Eddy generation induced by a line-shaped salt flux under a sea ice lead and associated salt transport are investigated using a three-dimensional numerical model. The model is designed to represent a typical condition for the wintertime Arctic Ocean mixed layer, where new ice formation within leads is known to be one of the primary sources of dense water. The result shows that along-lead baroclinic jets generate anticyclonic eddies at the base of the mixed layer, and almost all the lead-originated salt is contained inside these eddies. These eddies survive for over a month after closing of the lead and transport the lead-originated salt laterally. Consequently, the lead-origin salt settles only on the top of the halocline and is not used for increasing salinity of the mixed layer. Sensitivity experiments suggest that the horizontal scale of generated eddies depends only on the surface forcing and is proportional to the cube root of the total amount of salt input. This scaling of eddy size is consistent with a theoretical argument based on a linear instability theory. Parameterizing these processes would improve representation of the Arctic Ocean mixed layer in ocean general circulation models.

scholarly journals Mechanisms influencing seasonal-to-interannual prediction skill of sea ice extent in the Arctic Ocean in MIROC

2017 ◽  
Author(s):  
Jun Ono ◽  
Hiroaki Tatebe ◽  
Yoshiki Komuro ◽  
Masato I. Nodzu ◽  
Masayoshi Ishii
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Barents Sea ◽  
Heat Content ◽  
The Arctic ◽  
Subsurface Water ◽  
Lead Times ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
The Arctic Ocean

Abstract. To assess the skill of predictions of the seasonal-to-interannual detrended sea ice extent in the Arctic Ocean (SIEAO) and to clarify the underlying physical processes, we conducted ensemble hindcasts, started on January 1st, April 1st, July 1st, and October 1st for each year from 1980 to 2011, for lead times of up three years, using the Model for Interdisciplinary Research on Climate (MIROC) version 5 initialized with the observed atmosphere and ocean anomalies and sea ice concentration. Significant skill is found for the winter months: the December SIEAO can be predicted up to 1 year ahead. This skill is attributed to the subsurface ocean heat content originating in the North Atlantic. The subsurface water flows into the Barents Sea from spring to fall and emerges at the surface in winter by vertical mixing, and eventually affects the sea ice variability there. Meanwhile, the September SIEAO predictions are skillful for lead times of up to 3 months, due to the persistence of sea ice in the Beaufort, Chukchi, and East Siberian Seas initialized in July, as suggested by previous studies.

scholarly journals Arctic freshwater fluxes: sources, tracer budgets and inconsistencies

2019 ◽  
Vol 13 (8) ◽  
pp. 2111-2131
Author(s):  
Alexander Forryan ◽  
Sheldon Bacon ◽  
Takamasa Tsubouchi ◽  
Sinhué Torres-Valdés ◽  
Alberto C. Naveira Garabato
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Inorganic Nutrients ◽  
The Arctic ◽  
Freshwater Flux ◽  
Geochemical Tracers ◽  
Ice Melt ◽  
Boundary Velocity ◽  
The Arctic Ocean ◽  
Geochemical Method

Abstract. The net rate of freshwater input to the Arctic Ocean has been calculated in the past by two methods: directly, as the sum of precipitation, evaporation and runoff, an approach hindered by sparsity of measurements, and by the ice and ocean budget method, where the net surface freshwater flux within a defined boundary is calculated from the rate of dilution of salinity, comparing ocean inflows with ice and ocean outflows. Here a third method is introduced, the geochemical method, as a modification of the budget method. A standard approach uses geochemical tracers (salinity, oxygen isotopes, inorganic nutrients) to compute “source fractions” that quantify a water parcel's constituent proportions of seawater, freshwater of meteoric origin, and either sea ice melt or brine (from the freezing-out of sea ice). The geochemical method combines the source fractions with the boundary velocity field of the budget method to quantify the net flux derived from each source. Here it is shown that the geochemical method generates an Arctic Ocean surface freshwater flux, which is also the meteoric source flux, of 200±44 mSv (1 Sv=106 m3 s−1), statistically indistinguishable from the budget method's 187±44 mSv, so that two different approaches to surface freshwater flux calculation are reconciled. The freshwater export rate of sea ice (40±14 mSv) is similar to the brine export flux, due to the “freshwater deficit” left by the freezing-out of sea ice (60±50 mSv). Inorganic nutrients are used to define Atlantic and Pacific seawater categories, and the results show significant non-conservation, whereby Atlantic seawater is effectively “converted” into Pacific seawater. This is hypothesized to be a consequence of denitrification within the Arctic Ocean, a process likely becoming more important with seasonal sea ice retreat. While inorganic nutrients may now be delivering ambiguous results on seawater origins, they may prove useful to quantify the Arctic Ocean's net denitrification rate. End point degeneracy is also discussed: multiple property definitions that lie along the same “mixing line” generate confused results.

scholarly journals Arctic circulation regimes

2015 ◽  
Vol 373 (2052) ◽  
pp. 20140160 ◽  
Author(s):  
Andrey Proshutinsky ◽  
Dmitry Dukhovskoy ◽  
Mary-Louise Timmermans ◽  
Richard Krishfield ◽  
Jonathan L. Bamber
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Decadal Variability ◽  
Environmental Parameters ◽  
The Arctic ◽  
Upper Ocean ◽  
Freshwater Flux ◽  
Freshwater Fluxes ◽  
The Arctic Ocean ◽  
Arctic Atmosphere

Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability.

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