Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation
Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation
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DOI：
10.5194/bg-9-1957-2012
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发表时间：
2012-01-01
期刊：
影响因子：
4.9
通讯作者：
Sogaard, D. H.
中科院分区：
文献类型：
--
作者：
Long, M. H.;Koopmans, D.;Sogaard, D. H.
本研究利用涡动相关技术研究了冰水界面通量。温度涡动相关系统被用来确定冰融化和冻结的速率，和O-2涡动相关系统被用来检查O-2交换率驱动的生物和物理过程。这项研究于2010年3月中旬在格陵兰岛西南部峡湾的0.7米厚的海冰下进行，结果显示冰的融化率很低，最高为0.80毫米日（-1）。与释放的O-2贫融水的O-2通量小于13%的平均每日O-2呼吸速率。冰融化和不充分的垂直湍流混合，由于低流速造成的定期分层立即低于冰。这阻止了通量的确定61%的部署时间。通过检查累积通量的速度、线性和稳定性来确定这些时间间隔。通过垂直速度和O-2光谱及其cospectric的非分层条件的检查显示发达的湍流的特征指纹。从所测得的O-2通量的光合作用/辐照度曲线，建立了最小二乘拟合。这种关系表明净光合作用的光限制开始于4.2 μ mol光子m（-2）s（-1），藻类群落很好地适应了低光条件，因为在早春时期，它们有75%的时间处于光饱和状态。然而，海冰相关的微生物和藻类群落是净异养的，每日总初级生产量为0.69 mmol O-2 m（-2）d（-1），呼吸速率为-2.13 mmol O-2 m（-2）d（-1），导致净生态系统代谢为-1.45 mmol O-2 m（-2）d（-1）。涡动相关技术的这种应用产生了高时间分辨率的O-2通量和冰融化速率，在不干扰现场环境条件的情况下进行测量，同时在大约50米（2）的区域内进行积分，其中包括海冰群落的高度可变活动和空间分布。
This study examined fluxes across the ice-water interface utilizing the eddy correlation technique. Temperature eddy correlation systems were used to determine rates of ice melting and freezing, and O-2 eddy correlation systems were used to examine O-2 exchange rates driven by biological and physical processes. The study was conducted below 0.7m thick sea-ice in mid-March (2)010 in a southwest Greenland fjord and revealed low rates of ice melt at a maximum of 0.80mmd(-1). The O-2 flux associated with release of O-2 depleted melt water was less than 13% of the average daily O-2 respiration rate. Ice melt and insufficient vertical turbulent mixing due to low current velocities caused periodic stratification immediately below the ice. This prevented the determination of fluxes 61% of the deployment time. These time intervals were identified by examining the velocity and the linearity and stability of the cumulative flux. The examination of unstratified conditions through vertical velocity and O-2 spectra and their cospectra revealed characteristic fingerprints of well-developed turbulence. From the measured O-2 fluxes a photosynthesis/ irradiance curve was established by least-squares fitting. This relation showed that light limitation of net photosynthesis began at 4.2 mu mol photons m(-2) s(-1), and that algal communities were well-adapted to low-light conditions as they were light saturated for 75% of the day during this early spring period. However, the sea-ice associated microbial and algal community was net heterotrophic with a daily gross primary production of 0.69 mmol O-2 m(-2) d(-1) and a respiration rate of -2.13 mmol O-2 m(-2) d(-1) leading to a net ecosystem metabolism of -1.45 mmol O-2 m(-2) d(-1). This application of the eddy correlation technique produced high temporal resolution O-2 fluxes and ice melt rates that were measured without disturbing the in situ environmental conditions while integrating over an area of approximately 50m(2) which incorporated the highly variable activity and spatial distributions of sea-ice communities.