Recent changes in the Labrador Sea Water within the Deep Western Boundary Current southeast of Cape Cod
- 標題
- Recent changes in the Labrador Sea Water within the Deep Western Boundary Current southeast of Cape Cod
- 作者
- Deep western boundary current; Labrador sea water; Variability; Transport; Potential vorticity
- 文件屬性
- 國外期刊
- 知識分類
- 基礎研究
- 出版年
- 2011
- 刊名
- Deep Sea Research Part I
- 關鍵字
- Deep western boundary current; Labrador sea water; Variability; Transport; Potential vorticity
- 點閱數
- 2593
摘要
Water properties measured by the central mooring in the Line W mooring array southeast of Cape Cod document a large character shift during the period of November 2001 to April 2008. The observed temperature, salinity and planetary potential vorticity (PPV) anomalies manifest changes in the formation region of the water masses present at Station W, specifically upper Labrador Sea Water (uLSW), deep Labrador Sea Water (dLSW) and Overflow Water (OW). During the observation period, the minimum in the PPV anomaly field relative to the record mean PPV profile migrated from 1500 m, where it was originally found, to 700 m. Temporal changes in the vertical distribution of temperature and salinity were correlated with the PPV changes. This suggests a dLSW-dominated first half of the record versus an uLSW-dominated second half. The structure of these anomalies is consistent with observations within the Labrador Sea, and their transit time to Line W agrees well with tracer-derived times for signals spreading along the western boundary. In that context, the observed water properties at Line W in the early 2000s reflected the intense deep convection in the Labrador Sea in the mid-1990s, with less intense convection subsequently affecting lighter isopycnals. The observed velocity field is dominated by high-frequency (periods of days to months) fluctuations, however, a fraction of the velocity variability is correlated with changes in water mass properties, and indicate a gradual acceleration of the southwestward flow, with a corresponding increase in Deep Western Boundary Current transport.