Physical Sciences

An artificial pool experiment in Antarctic sea ice: effects of sea ice melting on physical and biogeochemical components of pool water

Daiki Nomura^a1a2 p1 c1, Daisuke Simizu^a3, Suchana Chavanich^a4, Hideo Shinagawa^a5 and Mitsuo Fukuchi^a1

^a1 National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8501, Japan

^a2 Japan Society for the Promotion of Science (JSPS), 6 Ichiban-cho, Chiyoda, Tokyo 102-8471, Japan

^a3 Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-0819, Japan

^a4 Reef Biology Research Group, Department of Marine Science, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok 10330, Thailand

^a5 Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan

Abstract

We performed an artificial pool experiment in the Antarctic multi-year land-fast ice to examine and simulate the effect of sea ice melting on physical and biogeochemical components of the sea ice field. The input of snow and ice meltwater resulted in warmer, low salinity water at the surface of the pool and probably stratification of the less dense water. Current speed measurements also pointed to water stratification within the pool. Rapid phytoplankton growth in the pool resulted in drastic decreases in concentrations of dissolved inorganic carbon and nutrients (NO₃ ^- and Si(OH)₄) in the surface waters of the pool, particularly depleted for NO₃ ^-. There was high correlation between variations of dissolved inorganic carbon and nutrient concentrations, but the apparent uptake ratios of these components deviated from that generally applied to marine phytoplankton. The sequence of changes in the physical and biogeochemical components of the pool water suggests that the onset of rapid phytoplankton growth was closely related to the water stratification, which provided stable conditions for phytoplankton bloom even though the supply of nutrients from under-ice water would have declined.

(Received August 18 2011)

(Accepted February 26 2012)

(Online publication May 16 2012)

Key words

• dissolved inorganic carbon;
• nutrients;
• phytoplankton bloom;
• Southern Ocean;
• water stratification

Correspondence:

^c1 daiki.nomura@npolar.no

^p1 Current address: Norwegian Polar Institute, Fram Centre, NO-9296 Tromsø, Norway