scholarly journals Laboratory study of initial sea-ice growth: properties of grease ice and nilas

2012 ◽  
Vol 6 (4) ◽  
pp. 729-741 ◽  
Author(s):  
A. K. Naumann ◽  
D. Notz ◽  
L. Håvik ◽  
A. Sirevaag
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Solid Fraction ◽  
Interstitial Water ◽  
Mass Conservation ◽  
Ice Formation ◽  
Ice Thickness ◽  
Ice Growth ◽  
Bulk Salinity ◽  
A Current

Abstract. We investigate initial sea-ice growth in an ice-tank study by freezing an NaCl solution of about 29 g kg−1 in three different setups: grease ice grew in experiments with waves and in experiments with a current and wind, while nilas formed in a quiescent experimental setup. In this paper we focus on the differences in bulk salinity, solid fraction and thickness between these two ice types. The bulk salinity of the grease-ice layer in our experiments remained almost constant until the ice began to consolidate. In contrast, the initial bulk-salinity evolution of the nilas is well described by a linear decrease of about 2.1 g kg−1 h−1 independent of air temperature. This rapid decrease can be qualitatively understood by considering a Rayleigh number that became maximum while the nilas was still less than 1 cm thick. Comparing three different methods to measure solid fraction in grease ice based on (a) salt conservation, (b) mass conservation and (c) energy conservation, we find that the method based on salt conservation does not give reliable results if the salinity of the interstitial water is approximated as being equal to the salinity of the underlying water. Instead the increase in salinity of the interstitial water during grease-ice formation must be taken into account. In our experiments, the solid fraction of grease ice was relatively constant with values of 0.25, whereas it increased to values as high as 0.50 as soon as the grease ice consolidated at its surface. In contrast, the solid fraction of the nilas increased continuously in the first hours of ice formation and reached an average value of 0.55 after 4.5 h. The spatially averaged ice thickness was twice as large in the first 24 h of ice formation in the setup with a current and wind compared to the other two setups, since the wind kept parts of the water surface ice free and therefore allowed for a higher heat loss from the water. The development of the ice thickness can be reproduced well with simple, one dimensional models that only require air temperature or ice surface temperature as input.

scholarly journals Initial sea-ice growth in open water: properties of grease ice and nilas

2012 ◽  
Vol 6 (1) ◽  
pp. 125-158 ◽  
Author(s):  
A. K. Naumann ◽  
D. Notz ◽  
L. Håvik ◽  
A. Sirevaag
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Solid Fraction ◽  
Interstitial Water ◽  
Open Water ◽  
Ice Formation ◽  
Ice Thickness ◽  
Ice Growth ◽  
Bulk Salinity ◽  
A Current

Abstract. To investigate initial sea-ice growth in open water, we carried out an ice-tank study with three different setups: grease ice grew in experiments with waves and in experiments with a current and wind, while nilas formed in a quiescent experimental setup. In this paper we focus on the differences in bulk salinity, solid fraction and thickness between these two ice types. We find that the bulk salinity of the grease-ice layer remains almost constant until the ice starts to consolidate. In contrast, the bulk salinity of nilas is in the first hours of ice formation well described by a linear decrease of 2.1 g kg−1 h−1 independent of air temperature. Such rapid decrease in bulk salinity can be understood qualitatively in the light of a Rayleigh number, the maximum of which is reached while the nilas is still less than 1 cm thick. Comparing three different methods to measure solid fraction in grease ice based on (a) salt conservation, (b) mass conservation and (c) energy conservation, we find that the method based on salt conservation does not give reliable results if the salinity of the interstitial water is approximated as being equal to the salinity of the upper water layer. Instead the increase in salinity of the interstitial water during grease-ice formation must be taken into account. We find that the solid fraction of grease ice is relatively constant with values of 0.25, whereas it increases to values as high as 0.5 as soon as the grease ice consolidates at its surface. In contrast, the solid fraction of nilas increases continuously in the first hours of ice formation. The ice thickness is found to be twice as large in the first 24 h of ice formation in the setup with a current and wind compared to the other two setups, since the wind keeps parts of the water surface ice free. The development of the ice thickness can be reproduced well with simple, one dimensional models given only the air temperature or the ice surface temperature.

scholarly journals Seasonal changes of sea-ice characteristics off East Antarctica

1994 ◽  
Vol 20 ◽  
pp. 195-201 ◽  
Author(s):  
Ian Allison ◽  
Anthony Worby
Keyword(s):  
Sea Ice ◽  
Ice Cores ◽  
Open Water ◽  
Ice Formation ◽  
Ice Thickness ◽  
Spatial And Temporal Variability ◽  
Growth Season ◽  
Ice Growth ◽  
Antarctic Sea Ice ◽  
Ice Edge

Data on Antarctic sea‐ice characteristics, and their spatial and temporal variability, are presented from cruises between 1986 and 1993 for the region spanning 60°−150° E between October and May. In spring, the sea‐ice zone is a variable mixture of different thicknesses of ice plus open water and in some regions only 30−40% of the area is covered with ice >0.3 m thick. The thin‐ice and open‐water areas are important for air‐sea heat exchange. Crystallographic analyses of ice cores, supported by salinity and stable‐isotope measurements, show that approximately 50% of the ice mass is composed of small frazil crystals. These are formed by rapid ice growth in leads and polynyas and indicate the presence of open water throughout the growth season. The area‐averaged thickness of undeformed ice west of 120° E is typically less than 0.3 m and tends to‐increase with distance south of the ice edge. Ice growth by congelation freezing rarely exceeds 0.4 m, with increases in ice thickness beyond this mostly attributable to rafting and ridging. While most of the total area is thin ice or open water, in the central pack much of the total ice mass is contained in ridges. Taking account of the extent of ridging, the total area‐averaged ice thickness is estimated to be about 1m for the region 60°−90° E and 2 m for the region 120°−150° E. By December, new ice formation has ceased in all areas of the pack and only floes >0.3 m remain. In most regions these melt completely over the summer and the new season's ice formation starts in late February. By March, the thin ice has reached a thickness of 0.15 0.30 m, with nilas formation being an important mechanism for ice growth within the ice edge

scholarly journals Sea-ice growth in Ongul Strait, Antarctica

1993 ◽  
Vol 18 ◽  
pp. 97-101 ◽  
Author(s):  
Toshiyuki Κawamura ◽  
Κay I. Ohshima ◽  
Syuki Ushio ◽  
Takatoshi Takizawa
Keyword(s):  
Growth Rate ◽  
Sea Ice ◽  
Snow Cover ◽  
Snow Depth ◽  
Ice Cores ◽  
Ice Formation ◽  
Ice Thickness ◽  
Growth Processes ◽  
Ice Growth

A two-year study was conducted on the growth processes of sea ice in Ongul Strait, Antarctica. Routine measurements of snow depth and ice thickness were made and sea-ice cores were collected to assess their structure, temperature and salinity. The snow depth varied from 0 to about 1 m. In the winter months, the growth rate is higher in bare-ice regions than in snow-covered regions. However, over the year, the ice thickness itself is lower in the bare-ice regions than in the snow-covered regions. Sea ice in the snow-covered regions increased in thickness in spring rather than in winter, due to the formation of snow-ice and by ice formation related to the melting of snow cover.

scholarly journals Sea-ice growth in Ongul Strait, Antarctica

1993 ◽  
Vol 18 ◽  
pp. 97-101 ◽  
Author(s):  
Toshiyuki Κawamura ◽  
Κay I. Ohshima ◽  
Syuki Ushio ◽  
Takatoshi Takizawa
Keyword(s):  
Growth Rate ◽  
Sea Ice ◽  
Snow Cover ◽  
Snow Depth ◽  
Ice Cores ◽  
Ice Formation ◽  
Ice Thickness ◽  
Growth Processes ◽  
Ice Growth

A two-year study was conducted on the growth processes of sea ice in Ongul Strait, Antarctica. Routine measurements of snow depth and ice thickness were made and sea-ice cores were collected to assess their structure, temperature and salinity. The snow depth varied from 0 to about 1 m. In the winter months, the growth rate is higher in bare-ice regions than in snow-covered regions. However, over the year, the ice thickness itself is lower in the bare-ice regions than in the snow-covered regions. Sea ice in the snow-covered regions increased in thickness in spring rather than in winter, due to the formation of snow-ice and by ice formation related to the melting of snow cover.

scholarly journals Seasonal changes of sea-ice characteristics off East Antarctica

1994 ◽  
Vol 20 ◽  
pp. 195-201 ◽  
Author(s):  
Ian Allison ◽  
Anthony Worby
Keyword(s):  
Sea Ice ◽  
Ice Cores ◽  
Open Water ◽  
Ice Formation ◽  
Ice Thickness ◽  
Spatial And Temporal Variability ◽  
Growth Season ◽  
Ice Growth ◽  
Antarctic Sea Ice ◽  
Ice Edge

Data on Antarctic sea‐ice characteristics, and their spatial and temporal variability, are presented from cruises between 1986 and 1993 for the region spanning 60°−150° E between October and May. In spring, the sea‐ice zone is a variable mixture of different thicknesses of ice plus open water and in some regions only 30−40% of the area is covered with ice >0.3 m thick. The thin‐ice and open‐water areas are important for air‐sea heat exchange. Crystallographic analyses of ice cores, supported by salinity and stable‐isotope measurements, show that approximately 50% of the ice mass is composed of small frazil crystals. These are formed by rapid ice growth in leads and polynyas and indicate the presence of open water throughout the growth season. The area‐averaged thickness of undeformed ice west of 120° E is typically less than 0.3 m and tends to‐increase with distance south of the ice edge. Ice growth by congelation freezing rarely exceeds 0.4 m, with increases in ice thickness beyond this mostly attributable to rafting and ridging. While most of the total area is thin ice or open water, in the central pack much of the total ice mass is contained in ridges. Taking account of the extent of ridging, the total area‐averaged ice thickness is estimated to be about 1m for the region 60°−90° E and 2 m for the region 120°−150° E. By December, new ice formation has ceased in all areas of the pack and only floes >0.3 m remain. In most regions these melt completely over the summer and the new season's ice formation starts in late February. By March, the thin ice has reached a thickness of 0.15 0.30 m, with nilas formation being an important mechanism for ice growth within the ice edge

scholarly journals New insight from CryoSat-2 sea ice thickness for sea ice modelling

2018 ◽  
Author(s):  
David Schröder ◽  
Danny L. Feltham ◽  
Michel Tsamados ◽  
Andy Ridout ◽  
Rachel Tilling
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Arctic Sea Ice ◽  
Ice Thickness ◽  
Atmospheric Conditions ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
Ice Growth ◽  
Melt Pond ◽  
The Impact

Abstract. Estimates of Arctic sea ice thickness are available from the CryoSat-2 (CS2) radar altimetry mission during ice growth seasons since 2010. We derive the sub-grid scale ice thickness distribution (ITD) with respect to 5 ice thickness categories used in a sea ice component (CICE) of climate simulations. This allows us to initialize the ITD in stand-alone simulations with CICE and to verify the simulated cycle of ice thickness. We find that a default CICE simulation strongly underestimates ice thickness, despite reproducing the inter-annual variability of summer sea ice extent. We can identify the underestimation of winter ice growth as being responsible and show that increasing the ice conductive flux for lower temperatures (bubbly brine scheme) and accounting for the loss of drifting snow results in the simulated sea ice growth being more realistic. Sensitivity studies provide insight into the impact of initial and atmospheric conditions and, thus, on the role of positive and negative feedback processes. During summer, atmospheric conditions are responsible for 50 % of September sea ice thickness variability through the positive sea ice and melt pond albedo feedback. However, atmospheric winter conditions have little impact on winter ice growth due to the dominating negative conductive feedback process: the thinner the ice and snow in autumn, the stronger the ice growth in winter. We conclude that the fate of Arctic summer sea ice is largely controlled by atmospheric conditions during the melting season rather than by winter temperature. Our optimal model configuration does not only improve the simulated sea ice thickness, but also summer sea ice concentration, melt pond fraction, and length of the melt season. It is the first time CS2 sea ice thickness data have been applied successfully to improve sea ice model physics.

scholarly journals Compact Polarimetry Response to Modeled Fast Sea Ice Thickness

2020 ◽  
Vol 12 (19) ◽  
pp. 3240
Author(s):  
Mohammed Dabboor ◽  
Mohammed Shokr
Keyword(s):  
Sea Ice ◽  
Degree Of Polarization ◽  
Ice Thickness ◽  
Operational Mode ◽  
Sea Ice Thickness ◽  
Ice Growth ◽  
Bay Area ◽  
Fast Ice ◽  
Preliminary Study ◽  
Sar Imagery

Compact Polarimetric (CP) Synthetic Aperture Radar (SAR) is expected to gain more and more ground for Earth observation applications in the coming years. This comes in light of the recently launched RADARSAT Constellation Mission (RCM), which uniquely provides CP SAR imagery in operational mode. In this study, we present observations about the sensitivity of CP SAR imagery to thickness of thermodynamically-grown fast sea ice during early ice growth (September–December 2017) in the Resolute Bay area, Canadian Central Arctic. Fast ice is most suitable to use for this preliminary study since it exhibits only thermodynamic growth in absence of ice mobility and deformation. Results reveal that ice thickness up to 30 cm can be retrieved using several CP parameters from the tested set. This ice thickness corresponds to the thickness of young ice. We found the surface scattering mechanism to be dominant during the early ice growth, exposing an increasing tendency up to 30 cm thickness with a correlation coefficient with the thickness equal to 0.86. The degree of polarization was found to be the parameter with the highest correlation up to 0.95. While thickness retrieval within the same range is also possible using parameters from Full Polarimetric (FP) SAR parameters as shown in previous studies, the advantage of using CP SAR mode is the much larger swath coverage, which is an operational requirement.

scholarly journals Fate of sea ice in the 'New Arctic': A database of daily Lagrangian Arctic sea ice parcel drift tracks with coincident ice and atmospheric conditions

2021 ◽  
Author(s):  
Sean Horvath ◽  
Linette Boisvert ◽  
Chelsea Parker ◽  
Melinda Webster ◽  
Patrick Taylor ◽  
...  
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Mass Balance ◽  
Air Temperature ◽  
Snow Depth ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
Ice Mass Balance ◽  
Temperature And Pressure

Abstract. Since the early 2000s, sea ice has experienced an increased rate of decline in thickness and extent and transitioned to a seasonal ice cover. This shift to thinner, seasonal ice in the 'New Arctic' is accompanied by a reshuffling of energy flows at the surface. Understanding the magnitude and nature of this reshuffling and the feedbacks therein remains limited. A novel database is presented that combines satellite observations, model output, and reanalysis data with daily sea ice parcel drift tracks produced in a Lagrangian framework. This dataset consists of daily time series of sea ice parcel locations, sea ice and snow conditions, and atmospheric states. Building on previous work, this dataset includes remotely sensed radiative and turbulent fluxes from which the surface energy budget can be calculated. Additionally, flags indicate when sea ice parcels travel within cyclones, recording distance and direction from the cyclone center. The database drift track was evaluated by comparison with sea ice mass balance buoys. Results show ice parcels generally remain within 100km of the corresponding buoy, with a mean distance of 82.6 km and median distance of 54 km. The sea ice mass balance buoys also provide recordings of sea ice thickness, snow depth, and air temperature and pressure which were compared to this database. Ice thickness and snow depth typically are less accurate than air temperature and pressure due to the high spatial variability of the former two quantities when compared to a point measurement. The correlations between the ice parcel and buoy data are high, which highlights the accuracy of this Lagrangian database in capturing the seasonal changes and evolution of sea ice. This database has multiple applications for the scientific community; it can be used to study the processes that influence individual sea ice parcel time series, or to explore generalized summary statistics and trends across the Arctic. Applications such as these may shed light on the atmosphere-snow-sea ice interactions in the changing Arctic environment.

scholarly journals Interannual variability in Transpolar Drift ice thickness and potential impact of Atlantification

2020 ◽  
Author(s):  
H. Jakob Belter ◽  
Thomas Krumpen ◽  
Luisa von Albedyll ◽  
Tatiana A. Alekseeva ◽  
Sergei V. Frolov ◽  
...  
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
Fram Strait ◽  
Ice Growth ◽  
Arctic Sea ◽  
Transpolar Drift ◽  
The Impact

Abstract. Changes in Arctic sea ice thickness are the result of complex interactions of the dynamic and variable ice cover with atmosphere and ocean. Most of the sea ice exits the Arctic Ocean through Fram Strait, which is why long-term measurements of ice thickness at the end of the Transpolar Drift provide insight into the integrated signals of thermodynamic and dynamic influences along the pathways of Arctic sea ice. We present an updated time series of extensive ice thickness surveys carried out at the end of the Transpolar Drift between 2001 and 2020. Overall, we see a more than 20 % thinning of modal ice thickness since 2001. A comparison with first preliminary results from the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) shows that the modal summer thickness of the MOSAiC floe and its wider vicinity are consistent with measurements from previous years. By combining this unique time series with the Lagrangian sea ice tracking tool, ICETrack, and a simple thermodynamic sea ice growth model, we link the observed interannual ice thickness variability north of Fram Strait to increased drift speeds along the Transpolar Drift and the consequential variations in sea ice age and number of freezing degree days. We also show that the increased influence of upward-directed ocean heat flux in the eastern marginal ice zones, termed Atlantification, is not only responsible for sea ice thinning in and around the Laptev Sea, but also that the induced thickness anomalies persist beyond the Russian shelves and are potentially still measurable at the end of the Transpolar Drift after more than a year. With a tendency towards an even faster Transpolar Drift, winter sea ice growth will have less time to compensate the impact of Atlantification on sea ice growth in the eastern marginal ice zone, which will increasingly be felt in other parts of the sea ice covered Arctic.

scholarly journals An inter-comparison of the mass budget of the Arctic sea ice in CMIP6 models

2020 ◽  
Author(s):  
Ann Keen ◽  
Ed Blockley ◽  
David Bailey ◽  
Jens Boldingh Debernard ◽  
Mitchell Bushuk ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Formation ◽  
Mass Budget ◽  
Ice Growth ◽  
Arctic Sea ◽  
Basal Melting

Abstract. We compare the mass budget of the Arctic sea ice for 14 models submitted to the latest Climate Model Inter-comparison Project (CMIP6), using new diagnostics that have not been available for previous model inter-comparisons. Using these diagnostics allows us to look beyond the standard metrics of ice cover and thickness, to compare the processes of sea ice growth and loss in climate models in a more detailed way than has previously been possible. For the 1960–89 multi-model mean, the dominant processes causing annual ice growth are basal growth and frazil ice formation, which both occur during the winter. The main processes by which ice is lost are basal melting, top melting and advection of ice out of the Arctic. The first two processes occur in summer, while the latter process is present all year. The sea-ice budgets for individual models are strikingly similar overall in terms of the major processes causing ice growth and loss, and in terms of the time of year during which each process is important. However, there are also some key differences between the models. The relative amounts of frazil and basal ice formation varies between the models. This is, to some extent at least, attributable to exactly how the frazil growth is formulated within each model. There are also differences in the relative amounts of top and basal melting. As the ice cover and mass decline during the 21st century, we see a shift in the timing of the top and basal melting in the multi-model mean, with more melt occurring earlier in the year, and less melt later in the summer. The amount of basal growth in the autumn reduces, but the amount of basal growth later in the winter increases due to the ice being thinner. Overall, extra ice loss in May–June and reduced ice growth in October-November is partially offset by reduced ice melt in August and increased ice growth in January–February. For the individual models, changes in the budget components vary considerably in terms of magnitude and timing of change. However, when the evolving budget terms are considered as a function of the changing ice state itself, behaviours common to all the models emerge, suggesting that the sea ice components of the models are fundamentally responding in a broadly consistent way to the warming climate. Additional results from a forced ocean-ice model show that although atmospheric forcing is crucial for the sea ice mass budget, the sea ice physics also plays an important role.

Sign in / Sign up

Export Citation Format

Share Document