A modeling study of upper ocean winter processes in the Labrador Sea

Tang, Choon Yik; Gui, Q.; DeTracey, Brendan

doi:10.1029/1999jc900214

Cited by 12 publications

(6 citation statements)

References 30 publications

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“…In general, low temperature is associated with low salinity but extends further to the south. The spatial pattern of MLD in winter is in general agreement with that reported in the model study of Tang et al (1999) and observations of Lavender et al (2002) in which the maximum MLD is located just off the ice edge around 58°N in March. A significant feature in the important period for chlorophyll growth (March and April) is the large difference in MLD between the northern and central Labrador Sea.…”

Section: Mixed-layer Depth and Stratificationsupporting

confidence: 79%

Regional differences in the timing of the spring bloom in the Labrador Sea

Wu¹,

Platt²,

Tang³

et al. 2008

Mar. Ecol. Prog. Ser.

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The environmental factors that control the timing of the spring bloom in the Labrador Sea were investigated using ocean color data from satellites, historical oceanographic data and a primary production model. From the satellite data, the onset of the spring bloom was found to progress with the season from south to north, with the exception of the northern Labrador Sea. The onset for the northern Labrador Sea occurred at approximately the same time as in the southern Labrador Sea. Two possible factors for the regional differences were examined from the data: irradiance and mixedlayer depth (MLD). The early bloom in the northern Labrador Sea is related to the very shallow mixed layer associated with low-salinity water. The temporal variations of the mean chlorophyll concentration in 4 regions of the Labrador Sea (the Grand Banks, southern, central and northern Labrador Sea) during the growth phase of the spring bloom were modeled using a primary production model with MLD derived from historical temperature-salinity data. The temporal variations, in particular the early bloom in the northern Labrador Sea, were well reproduced by the model. A model sensitivity study showed that the onset of the spring bloom is highly sensitive to MLD. This confirms the finding from the data that MLD is a critical environmental factor for the spring bloom. The availability of the photosynthetically active radiation plays an important role, but is not a determining factor of the early bloom in the northern Labrador Sea. The sensitivity study also showed that pre-bloom oceanographic conditions and attenuation of light in water have a greater effect on the timing in a shallow mixed layer than in a deeper mixed layer. KEY WORDS: Spring bloom · Onset time · Mixed layer depth · Regional difference · Labrador SeaResale or republication not permitted without written consent of the publisher

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Section: Mixed-layer Depth and Stratificationsupporting

confidence: 79%

Regional differences in the timing of the spring bloom in the Labrador Sea

Wu¹,

Platt²,

Tang³

et al. 2008

Mar. Ecol. Prog. Ser.

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“…Figure 2 shows an example of monthly MLD and ILD values obtained using our methodology for the location (45°N, 30°W) in the North Atlantic Ocean. In general, the North Atlantic Ocean is one of the ocean regions where deep mixed layer formation is expected in winter [e.g., Kelly , 1994; Tang et al , 1999]. As expected, the ILD deepens as Δ T increases from 0.1°C to 1.0°C.…”

Section: Mixed Layer Processes and Mld Criterionmentioning

confidence: 76%

Mixed layer depth variability over the global ocean

2003

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[1] The spatial and monthly variability of the climatological mixed layer depth (MLD) for the global ocean is examined using the recently developed Naval Research Laboratory (NRL) Ocean Mixed Layer Depth (NMLD) climatologies. The MLD fields are constructed using the subsurface temperature and salinity data from the World Ocean Atlas 1994 . To minimize the limitations of these global data in the MLD determination, a simple mixing scheme is introduced to form a stable water column. Using these new data sets, global MLD characteristics are produced on the basis of an optimal definition that employs a densitybased criterion having a fixed temperature difference of ÁT = 0.8°C and variable salinity. Strong seasonality of MLD is found in the subtropical Pacific Ocean and at high latitudes, as well as a very deep mixed layer in the North Atlantic Ocean in winter and a very shallow mixed layer in the Antarctic in all months. Using the climatological monthly MLD and isothermal layer depth (ILD) fields from the NMLD climatologies, an annual mean ÁT field is presented, providing criteria for determining an ILD that is approximately equivalent to the optimal MLD. This enables MLD to be determined in cases where salinity data are not available. The validity of the correspondence between ILD and MLD is demonstrated using daily averaged subsurface temperature and salinity from two moorings: a Tropical Atmosphere Ocean array mooring in the western equatorial Pacific warm pool, where salinity stratification is important, and a Woods Hole Oceanographic Institute (WHOI) mooring in the Arabian Sea, where strongly reversing seasonal monsoon winds prevail. In the western equatorial Pacific warm pool the use of ILD criterion with an annual mean ÁT value of 0.3°C yields comparable results with the optimal MLD, while large ÁT values yield an overestimated MLD. An analysis of ILD and MLD in the WHOI mooring show that use of an incorrect ÁT criterion for the ILD may underestimate or overestimate the optimal MLD. Finally, use of the spatial annual mean ÁT values constructed from the NMLD climatologies can be used to estimate the optimal MLD from only subsurface temperature data via an equivalent ILD for any location over the global ocean.INDEX TERMS: 4227 Oceanography: General: Diurnal, seasonal, and annual cycles; 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes; 4572 Oceanography: Physical: Upper ocean processes; 4599 Oceanography: Physical: General or miscellaneous; KEYWORDS: mixed layer, isothermal layer, seasonal cycle, temperature, salinity, verification Citation: Kara, A. B., P. A. Rochford, and H. E. Hurlburt, Mixed layer depth variability over the global ocean,

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“…It originated from Fram Strait, traveled southward in the East Greenland Current, and freshened the central Labrador Sea [Dickson et al, 1988]. Numerical models such as those of Goosse et al [1997], Tang et al [1999], Wadley and Bigg [2002] simulate the connection between changes in freshwater fluxes (for example, caused by the "Great Salinity Anomaly") and convection, but these spatially coarse resolution models do not represent the coastal and rim-current systems in the Greenland and Labrador Seas [Sutherland and Pickart, 2008]. Koenigk et al [2007] use 20th-century and Intergovernmental Panel on Climate Change scenario runs for an investigation of the changing freshwater export out of the Arctic Ocean using a model with grid spacing of about 15 km around Greenland.…”

Section: Introductionmentioning

confidence: 99%

Nares Strait hydrography and salinity field from a 3‐year moored array

Rabe¹,

Münchow²,

Johnson³

et al. 2010

J. Geophys. Res.

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[1] Nares Strait to the west of Greenland facilitates the exchange of heat and freshwater between the Arctic and Atlantic Oceans. This study focuses on salinity, temperature, and density measurements from Nares Strait from a mooring array deployed from 2003 to 2006. Innovative moorings requiring novel analysis methods measured seawater properties near 80.5°N, at spacing sufficient to resolve the internal Rossby deformation radius. The 3-year mean geostrophic velocity has a surface-intensified southward flow of 0.20 m s −1 against the western side of the strait and a secondary core flowing southward at 0.14 m s −1 in the middle of the strait. Data show warm salty water on the Greenland side and cold fresher water on the Ellesmere Island side, especially in the top layers. There was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast. Ice was drifting in late summer, fall, and early winter with a strong surface-intensified geostrophic flow in the middle of the strait. Ice was land fast in late winter, spring, and early summer, when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait. Salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the Arctic Ocean. One particularly strong pulse occurred at the end of July 2005. For several days, steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the Arctic due to strong southward winds.Citation: Rabe, B., A. Münchow, H. L. Johnson, and H. Melling (2010), Nares Strait hydrography and salinity field from a 3-year moored array,

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A modeling study of upper ocean winter processes in the Labrador Sea

Cited by 12 publications

References 30 publications

Regional differences in the timing of the spring bloom in the Labrador Sea

Regional differences in the timing of the spring bloom in the Labrador Sea

Mixed layer depth variability over the global ocean

Nares Strait hydrography and salinity field from a 3‐year moored array

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