Climate Influence on Antarctic Sea Ice Formation Recorded through Remote Sensing

Abstract. Sea-ice extent variability, a measure based on satellite-derived sea ice concentration measurements, has traditionally been used as an essential climate variable to evaluate the impact of climate change on polar regions. However, concentration- based measurements of ice variability do not allow to discriminate the relative contributions made by thermodynamic and dynamic processes, prompting the need to use sea-ice drift products and develop alternative methods to quantify changes in sea ice dynamics that would indicate trends in Antarctic ice characteristics. Here, we present a new method to automate the detection of rotational drift features in Antarctic sea ice at daily timescales using currently available remote sensing ice motion products from EUMETSAT OSI SAF. Results show that there is a large discrepancy in the detection of cyclonic drift features between products, both in terms of intensity and year-to-year distributions, thus diminishing the confidence at which ice drift variability can be further analysed. Product comparisons showed that there was good agreement in detecting anticyclonic drift, and cyclonic drift features were measured to be 1.5–2.2 times more intense than anticyclonic features. The most intense features were detected by the merged product, suggesting that the processing chain used for this product could be injecting additional rotational momentum into the resultant drift vectors. We conclude that it is therefore necessary to better understand why the products lack agreement before further trend analysis of these drift features and their climatic significance can be assessed.

Download Full-text

Low Salinity and High-Level UV-B Radiation Reduce Single-Cell Activity in Antarctic Sea Ice Bacteria

Applied and Environmental Microbiology ◽

10.1128/aem.00829-09 ◽

2009 ◽

Vol 75 (23) ◽

pp. 7570-7573 ◽

Cited By ~ 13

Author(s):

Andrew Martin ◽

Julie Hall ◽

Ken Ryan

Keyword(s):

Sea Ice ◽

Metabolic Activity ◽

Cell Activity ◽

Ice Formation ◽

Freeze Thaw ◽

Low Salinity ◽

Antarctic Sea Ice ◽

Single Cell Activity ◽

Fast Ice ◽

High Level

ABSTRACT Experiments simulating the sea ice cycle were conducted by exposing microbes from Antarctic fast ice to saline and irradiance regimens associated with the freeze-thaw process. In contrast to hypersaline conditions (ice formation), the simulated release of bacteria into hyposaline seawater combined with rapid exposure to increased UV-B radiation significantly reduced metabolic activity.

Download Full-text

Antarctic Sea Ice Control on the Depth of North Atlantic Deep Water

Journal of Climate ◽

10.1175/jcli-d-18-0519.1 ◽

2019 ◽

Vol 32 (9) ◽

pp. 2537-2551 ◽

Cited By ~ 6

Author(s):

Louis-Philippe Nadeau ◽

Raffaele Ferrari ◽

Malte F. Jansen

Keyword(s):

Sea Ice ◽

Deep Water ◽

Formation Rate ◽

Deep Ocean ◽

Meridional Overturning Circulation ◽

Ice Formation ◽

Overturning Circulation ◽

Antarctic Sea Ice ◽

Meridional Overturning

Abstract Changes in deep-ocean circulation and stratification have been argued to contribute to climatic shifts between glacial and interglacial climates by affecting the atmospheric carbon dioxide concentrations. It has been recently proposed that such changes are associated with variations in Antarctic sea ice through two possible mechanisms: an increased latitudinal extent of Antarctic sea ice and an increased rate of Antarctic sea ice formation. Both mechanisms lead to an upward shift of the Atlantic meridional overturning circulation (AMOC) above depths where diapycnal mixing is strong (above 2000 m), thus decoupling the AMOC from the abyssal overturning circulation. Here, these two hypotheses are tested using a series of idealized two-basin ocean simulations. To investigate independently the effect of an increased latitudinal ice extent from the effect of an increased ice formation rate, sea ice is parameterized as a latitude strip over which the buoyancy flux is negative. The results suggest that both mechanisms can effectively decouple the two cells of the meridional overturning circulation (MOC), and that their effects are additive. To illustrate the role of Antarctic sea ice in decoupling the AMOC and the abyssal overturning cell, the age of deep-water masses is estimated. An increase in both the sea ice extent and its formation rate yields a dramatic “aging” of deep-water masses if the sea ice is thick and acts as a lid, suppressing air–sea fluxes. The key role of vertical mixing is highlighted by comparing results using different profiles of vertical diffusivity. The implications of an increase in water mass ages for storing carbon in the deep ocean are discussed.

Download Full-text

Seasonal changes of sea-ice characteristics off East Antarctica

Annals of Glaciology ◽

10.1017/s026030550001644x ◽

1994 ◽

Vol 20 ◽

pp. 195-201 ◽

Cited By ~ 2

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

Download Full-text

Remote Sensing of Antarctic Sea Ice with Coordinated Aircraft and Satellite Data Acquisitions

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss.2018.8518550 ◽

2018 ◽

Cited By ~ 3

Author(s):

Son Nghiem ◽

Thomas Busche ◽

Thomas Kraus ◽

Markus Bachmann ◽

Nathan Kurtz ◽

...

Keyword(s):

Remote Sensing ◽

Sea Ice ◽

Satellite Data ◽

Antarctic Sea Ice

Download Full-text

Spatially distributed simulations of the effect of snow on mass balance and flooding of Antarctic sea ice

Journal of Glaciology ◽

10.1017/jog.2021.54 ◽

2021 ◽

pp. 1-19

Author(s):

Nander Wever ◽

Katherine Leonard ◽

Ted Maksym ◽

Seth White ◽

Martin Proksch ◽

...

Keyword(s):

Sea Ice ◽

Mass Balance ◽

Single Point ◽

Weddell Sea ◽

Ice Formation ◽

Ice Thickness ◽

One Dimensional ◽

Antarctic Sea Ice ◽

Distributed Simulations ◽

Snow And Ice

Abstract Southern Ocean sea ice can exhibit widespread flooding and subsequent snow-ice formation, due to relatively thick snow covers compared to the total ice thickness. Considerable subkilometer scale variability in snow and ice thickness causes poorly constrained uncertainties in determining the amount of flooding that occurs. Using datasets of snow depth and ice thickness acquired in the Weddell Sea during austral winter 2013 (AWECS campaign) from three floes, we demonstrate large spatial variability of a factor 10 and 5 for snow and combined snow and ice thickness, respectively. The temporal evolution after the floe visit was recorded by automatic weather station and ice mass balance buoys. Using a physics-based, multi-layer snow/sea ice model in a one-dimensional and distributed mode to simulate the thermodynamic processes, we show that the distributed simulations, modeling flooding across the entire heterogeneous floe, produced vastly different amounts of flooding than one-dimensional single point simulations. Three times the flooding is produced in the one-dimensional simulation for the buoy location than distributed (floe-averaged) simulations. The latter is in close agreement with buoy observations. The results suggest that using point observations or one-dimensional simulations to extrapolate processes on the floe-scale can overestimate the amount of flooding and snow-ice formation.

Download Full-text

High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

Biogeosciences ◽

10.5194/bg-5-865-2008 ◽

2008 ◽

Vol 5 (3) ◽

pp. 865-873 ◽

Cited By ~ 36

Author(s):

K. Junge ◽

B. D. Swanson

Keyword(s):

High Resolution ◽

Sea Ice ◽

Freezing Point ◽

Free Fall ◽

Ice Nucleation ◽

Survival Strategies ◽

Cloud Formation ◽

Ice Formation ◽

Bacterial Cells ◽

Antarctic Sea Ice

Abstract. Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for ice formation in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium – which for artificial seawater was –42.2±0.3°C. Our results suggest that immersion freezing of these marine psychro-active bacteria and viruses would not be important for heterogeneous ice nucleation processes in polar clouds or to the formation of sea ice. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

Download Full-text

Effects of the snow cover on Antarctic sea ice and potential modulation of its response to climate change

Annals of Glaciology ◽

10.3189/s0260305500016086 ◽

1995 ◽

Vol 21 ◽

pp. 369-376 ◽

Cited By ~ 13

Author(s):

Hajo Eicken ◽

Holger Fischer ◽

Peter Lemke

Keyword(s):

Climate Change ◽

Sea Ice ◽

Snow Cover ◽

Field Data ◽

Sea Water ◽

Weddell Sea ◽

Ice Formation ◽

Average Thickness ◽

One Dimensional ◽

Antarctic Sea Ice

Based on presented field data, it is shown that snow contributes roughly 8% to the total mass of ice in the Weddell Sea. Snow depth averages 0.16 m on first-year ice (average thickness 0.75 m) and 0.53 m on second-year ice (average thickness 1.70 m). Due to snow loading, sea ice is depressed below water level and flooded by sea water. As a result of flooding, snow ice forms through congelation of sea water and brine in a matrix of meteoric ice (i.e. snow). Sea-ice growth has been simulated with a one-dimensional model, treating the evolution of salinity, porosity and thermal properties of the ice. Simulations demonstrate that in the presence of a snow cover, ice growth is significantly reduced. Brine volumes increase by a factor of 1.5–2, affecting properties such as ice strength. Snow-ice formation depends on the evolution of freeboard and ice permeability. Effects of accumulation-rate changes have been assessed, for the Weddell Sea with a large-scale sea-ice model accounting for snow-ice formation. Results for different scenarios are presented and compared with field data and one-dimensional simulations. The role of snow in modulating the response of Antarctic sea ice to climate change is discussed.

Download Full-text