Stephen F. Ackley

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The sea ice does not only determine the ecology of ice biota, but it also influences the pelagic systems under the ice cover and at ice edges. In this paper, new estimates of Arctic and Antarctic production of biogenic carbon are derived, and differences as well as similarities between the two oceans are examined. In ice-covered seas, high algal(More)
An autumn bloom of sea-ice algae was observed from February to June of 1992 within the upper 0.4 meter of multiyear ice in the Western Weddell Sea, Antarctica. The bloom was reliant on the freezing of porous areas within the ice that initiated a vertical exchange of nutrient-depleted brine with nutrient-rich seawater. This replenishment of nutrients to the(More)
Sea-ice conditions were observed using the ASPeCt observation protocol on three cruises in the Ross Sea spanning the Antarctic summer season (APIS, December 1999–February 2000; AnSlope 1, March–April 2003; AnSlope 2, February–April 2004). An additional dataset was analyzed from helicopter video surveys taken during the APIS cruise. The helicopter video was(More)
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[1] An internal ‘‘gap’’ layer of deteriorated sea ice is colocated with a significant microbial biological community in late first year and second year Antarctic sea ice in summer. We modeled gap layer formation using a thermal flux model based on the summer reversal in thermal gradient and the thermal conductivity found in the upper ice column. The(More)
This paper discusses a method for using the reflected signal from a stepped-frequency radar system to obtain the electrical permittivity and conductivity in a thin layer at the flat surface of a (possibly inhomogeneous) body. The method is based on a band-limited version of geometrical optics. # 1999 IMACS/Elsevier Science B.V. All rights reserved.
Cores and brine samples from sea ice of the Weddell Sea were analyzed for nutrients (phosphate, nitrate and silicate), salinity and chlorophyll a during winter. Stratigraphic analyses of the cores were also carried out. Bulk nutrient concentrations in the sea ice fluctuated widely and did not correlate with salinity. Nutrient concentrations in cores were(More)
Antarctic summer sea ice concentration and extent: comparison of ODEN 2006 ship observations, satellite passive microwave and NIC sea ice charts B. Ozsoy-Cicek, H. Xie, S. F. Ackley, and K. Ye Laboratory for Remote Sensing and Geoinformatics, Department of Geological Sciences, University of Texas at San Antonio, Texas 78249, USA Department of Management(More)
Although sea ice extent in the Bellingshausen-Amundsen (BA) seas sector of the Antarctic has shown significant decline over several decades, there is not enough data to draw any conclusion on sea ice thickness and its change for the BA sector, or for the entire Southern Ocean. This paper first presents our results of snow and ice thickness distributions(More)
High-spatial-resolution aerial photographs can provide detailed distribution of sea ice features. However, very few studies have ever considered shadows on the photographs for sea ice detection. In this letter, sea ice shadows, retrieved from 163 selected aerial photographs acquired on July 26, 2010, in a marginal-ice-zone area near Barrow, Alaska,(More)