Sea Ice Ecology Research
Geophysical Constraints on Sea-Ice Bacteria: Implications for Life on Ice-Covered Solar Bodies
As sea ice cools, the small-scale (mm to sub-mm size) brine inclusions decrease in size due to brine freezing out of solution. At a liquid volume fraction of around 50 to 70 ppt, brine layers are generally assumed to segregate into isolated pores. This process is believed to be critical for sea-ice permeability, with much lower permeabilities at lower ice temperatures corresponding to isolated pores.
It has been hypothesized that upon warming of the ice the isolated brine pockets do not assume the original planar shape but grow as spherical or slightly oblong inclusions, thereby maintaining a state of separate pores to higher temperatures and brine volume fractions than observed during the original cooling.
Such segregation at the pore scale is extremely important for organisms residing within the ice matrix, as they would be effectively cut off from the supply of nutrients or other dissolved/particulate matter as well as prevented from interacting with each other in the "segregated-pore" regime. The transition between a connected pore system and a segregated, isolated pore system hence represents an important transition. This becomes even more important for would-be habitats such as the briny ice on the Jovian moon Europa, where the issues of temporal and spatial scales in the potential evolution and survival of life are critical.
Physical-biological control of primary production in Beaufort and Chukchi Sea ice: Its contribution to shelf-basin interactions in the Western Arctic
This project is part of the Western Arctic Shelf-Basin Interactions (SBI) program funded by the National Science Foundation (NSF). Linkages between physical, chemical and biological oceanography are being studied in the Chukchi and Beaufort Seas with the intent to quantify sea ice primary production. Field studies, experimental work, remote sensing and modeling efforts are combined to verify how light and nutrient supply control the magnitude of biomass formation within the sea ice.
Changes in the Spring Sea Ice Concentration in the Bering Sea from 1972-2000 in Relation to Spotted Seal (Phoca largha) Reproductive Success
This is the title of Candace Picco's MS thesis. Spotted seals are most dependent on the seasonal sea ice in the Bering Sea during the spring pupping and mating season. Changes in sea ice characteristics, as related to recent documented changes in climate, may have an effect on the population status of ice-associated species, such as the spotted seal. This study investigates the effects of climate change on the spatial and temporal patterns of the spring sea ice concentration in the Bering Sea from 1972-2000 in relation to changes in the reproductive success of the spotted seal (Phoca largha). Multinomial time-series regressions were used to determine the influence of different climatic variables on the sea ice concentration. Generalized Estimating Equations were used to compare the ice conditions of defined regions in the Bering Sea and the reproductive success of the spotted seal for 20 years from 1964-2003. The results showed no definitive patterns relating the monthly climatic variables and sea ice concentration averages; however, noticeable trends in sea ice included evidence of an earlier and more variable spring, an overall decrease in ice concentration since 1986/1987, and a more rapid response of sea ice to “regime shifts”. Seal analysis showed an increase in reproductive success in the 1980’s and 1998, which coincided with a boom in groundfish biomass, and a decrease in reproductive success from 2000 to 2003, which was concurrent with the warmest temperatures on record and a subsequent decrease in sea ice concentration in the Bering Sea. Additionally, seals were found to have a lower reproductive rate during “heavy” ice conditions and in the eastern regions of the Bering Sea. This study showed that seal reproductive success and sea ice concentration varied temporally and spatially, the direct causality of these variations was uncertain.
Can microorganisms, especially Melosira arctica, significantly alter the physical properties of sea ice and to what biological advantage?