A first look at skewness in the Labrador sea water masses

McLarty, Jennifer L. (2008) A first look at skewness in the Labrador sea water masses. Masters thesis, Memorial University of Newfoundland.

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Abstract

Hydrographic data from 1938 to 2006 in the Labrador Sea is used to calculate the geographical distribution of standard deviation (δ) and moment coefficient of skewness (γ3) of the salinity (S) anomaly, potential temperature (θ) anomaly, and potential density anomaly (σθ) fields of the six major water masses. After removing the mean monthly signal, the data statistics are calculated in 22 separate regions and respectively defined at the region centres, thereby allowing us to interpolate the data to a 0.5° x 0.5° grid in the Labrador Sea for each water mass. While the δ maps describe the geographical distribution of variability at all scales, we show that the skewness of the low-frequency S and θ fields can be used to distinguish the mesoscale variability; mixing of θ - S characteristics in the classic Labrador Sea processes are prominent in the S and θ skewness maps. Sensitivity of skewness to the long-term variability is tested by calculating the δ and γ₃ maps for four shorter time periods: 1938-1984 and 1985-2006 in which sea-water properties are subject to different long-term variability (compared to 1938-2006), and 1963-1973 and 1989-1999 in which sea-water properties are nearly homogeneous. Although statistically insignificant skew dominates the distributions in 1963-1973 and 1989-1999, the results show remarkable similarity between the five γ₃(S) and γ₃(θ) maps of the surface layer, Irminger Water layer, shallow Labrador Sea Water layer, and to some extent the deep Labrador Sea Water layer. We conclude the geographical distribution of S and θ skewness does distinguish the mesoscale variability in the Labrador Sea and likely does not exhibit interannual variability.

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