scholarly journals Winter mixed-layer development in the central Irminger Sea : the effect of strong, intermittent wind events

2006 ◽  
Author(s):  
Kjetil Vage
Keyword(s):  
Mixed Layer ◽  
Irminger Sea ◽  
Winter Mixed Layer ◽  
Wind Events ◽  
Layer Development

scholarly journals Winter Mixed Layer Development in the Central Irminger Sea: The Effect of Strong, Intermittent Wind Events

2008 ◽  
Vol 38 (3) ◽  
pp. 541-565 ◽  
Author(s):  
Kjetil Våge ◽  
Robert S. Pickart ◽  
G. W. K. Moore ◽  
Mads Hvid Ribergaard
Keyword(s):  
Mixed Layer ◽  
Deep Convection ◽  
Layer Model ◽  
Pressure System ◽  
Nao Index ◽  
Irminger Sea ◽  
Wind Events ◽  
Upper Level ◽  
The Impact ◽  
Mixed Layer Model

Abstract The impact of the Greenland tip jet on the wintertime mixed layer of the southwest Irminger Sea is investigated using in situ moored profiler data and a variety of atmospheric datasets. The mixed layer was observed to reach 400 m in the spring of 2003 and 300 m in the spring of 2004. Both of these winters were mild and characterized by a low North Atlantic Oscillation (NAO) index. A typical tip jet event is associated with a low pressure system that is advected by upper-level steering currents into the region east of Cape Farewell and interacts with the high topography of southern Greenland. Heat flux time series for the mooring site were constructed that include the enhancing influence of the tip jet events. This was used to force a one-dimensional mixed layer model, which was able to reproduce the observed envelope of mixed layer deepening in both winters. The deeper mixed layer of the first winter was largely due to a higher number of robust tip jet events, which in turn was caused by the steering currents focusing more storms adjacent to southern Greenland. Application of the mixed layer model to the winter of 1994–95, a period characterized by a high-NAO index, resulted in convection exceeding 1700 m. This prediction is consistent with hydrographic data collected in summer 1995, supporting the notion that deep convection can occur in the Irminger Sea during strong winters.

scholarly journals Winter Atmospheric Buoyancy Forcing and Oceanic Response during Strong Wind Events around Southeastern Greenland in the Regional Arctic System Model (RASM) for 1990–2010*

2016 ◽  
Vol 29 (3) ◽  
pp. 975-994 ◽  
Author(s):  
Alice K. DuVivier ◽  
John J. Cassano ◽  
Anthony Craig ◽  
Joseph Hamman ◽  
Wieslaw Maslowski ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Deep Convection ◽  
Heat Fluxes ◽  
System Model ◽  
Strong Wind ◽  
Self Organizing Map ◽  
Ocean Mixed Layer ◽  
Irminger Sea ◽  
Wind Events ◽  
Wind Patterns

Abstract Strong, mesoscale tip jets and barrier winds that occur along the southeastern Greenland coast have the potential to impact deep convection in the Irminger Sea. The self-organizing map (SOM) training algorithm was used to identify 12 wind patterns that represent the range of winter [November–March (NDJFM)] wind regimes identified in the fully coupled Regional Arctic System Model (RASM) during 1990–2010. For all wind patterns, the ocean loses buoyancy, primarily through the turbulent sensible and latent heat fluxes; haline contributions to buoyancy change were found to be insignificant compared to the thermal contributions. Patterns with westerly winds at the Cape Farewell area had the largest buoyancy loss over the Irminger and Labrador Seas due to large turbulent fluxes from strong winds and the advection of anomalously cold, dry air over the warmer ocean. Similar to observations, RASM simulated typical ocean mixed layer depths (MLD) of approximately 400 m throughout the Irminger basin, with individual years experiencing MLDs of 800 m or greater. The ocean mixed layer deepens over most of the Irminger Sea following wind events with northerly flow, and the deepening is greater for patterns of longer duration. Seasonal deepest MLD is strongly and positively correlated to the frequency of westerly tip jets with northerly flow.

Winter mixed layer entrainment of Weddell Deep Water

1984 ◽  
Vol 89 (C1) ◽  
pp. 637 ◽  
Author(s):  
A. L. Gordon ◽  
C. T. A. Chen ◽  
W. G. Metcalf
Keyword(s):  
Mixed Layer ◽  
Deep Water ◽  
Winter Mixed Layer

scholarly journals Diagnosing Natural Variability of North Atlantic Water Masses in HadCM3

2005 ◽  
Vol 18 (12) ◽  
pp. 1925-1941 ◽  
Author(s):  
Keith Haines ◽  
Chris Old
Keyword(s):  
Mixed Layer ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Mode Water ◽  
Surface Heat Fluxes ◽  
Mode Waters ◽  
Winter Mixed Layer

Abstract A study of thermally driven water mass transformations over 100 yr in the ocean component of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is presented. The processes of surface-forced transformations, subduction and mixing, both above and below the winter mixed layer base, are quantified. Subtropical Mode Waters are formed by surface heat fluxes and subducted at more or less the same rate. However, Labrador Seawater and Nordic Seawater classes (the other main subduction classes) are primarily formed by mixing within the mixed layer with very little formation directly from surface heat fluxes. The Subpolar Mode Water classes are dominated by net obduction of water back into the mixed layer from below. Subtropical Mode Water (18°C) variability shows a cycle of formation by surface fluxes, subduction ∼2 yr later, followed by mixing with warmer waters below the winter mixed layer base during the next 3 yr, and finally obduction back into the mixed layer at 21°C, ∼5 yr after the original formation. Surface transformation of Subpolar Mode Waters, ∼12°C, are led by surface transformations of warmer waters by up to 5 yr as water is transferred from the subtropical gyre. They are also led by obduction variability from below the mixed layer, by ∼2 yr. The variability of obduction in Subpolar Mode Waters also appears to be preceded, by 3–5 yr, by variability in subduction of Labrador Sea Waters at ∼6°C. This supports a mechanism in which southward-propagating Labrador seawater anomalies below the subpolar gyre can influence the upper water circulation and obduction into the mixed layer.

Temporal variations of the winter mixed layer south of the Kuroshio Extension

2010 ◽  
Vol 66 (1) ◽  
pp. 147-153 ◽  
Author(s):  
Hikaru Iwamaru ◽  
Fumiaki Kobashi ◽  
Naoto Iwasaka
Keyword(s):  
Mixed Layer ◽  
Kuroshio Extension ◽  
Temporal Variations ◽  
Winter Mixed Layer ◽  
The Kuroshio

scholarly journals Subduction over the Southern Indian Ocean in a High-Resolution Atmosphere–Ocean Coupled Model

2011 ◽  
Vol 24 (15) ◽  
pp. 3830-3849 ◽  
Author(s):  
Mei-Man Lee ◽  
A. J. George Nurser ◽  
I. Stevens ◽  
Jean-Baptiste Sallée
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Current System ◽  
Mixed Layer Depth ◽  
Coupled Model ◽  
Horizontal Resolution ◽  
Layer Depth ◽  
Mode Water ◽  
Coarse Resolution ◽  
Winter Mixed Layer

Abstract This study examines the subduction of the Subantarctic Mode Water in the Indian Ocean in an ocean–atmosphere coupled model in which the ocean component is eddy permitting. The purpose is to assess how sensitive the simulated mode water is to the horizontal resolution in the ocean by comparing with a coarse-resolution ocean coupled model. Subduction of water mass is principally set by the depth of the winter mixed layer. It is found that the path of the Agulhas Current system in the model with an eddy-permitting ocean is different from that with a coarse-resolution ocean. This results in a greater surface heat loss over the Agulhas Return Current and a deeper winter mixed layer downstream in the eddy-permitting ocean coupled model. The winter mixed layer depth in the eddy-permitting ocean compares well to the observations, whereas the winter mixed layer depth in the coarse-resolution ocean coupled model is too shallow and has the wrong spatial structure. To quantify the impacts of different winter mixed depths on the subduction, a way to diagnose local subduction is proposed that includes eddy subduction. It shows that the subduction in the eddy-permitting model is closer to the observations in terms of the magnitudes and the locations. Eddies in the eddy-permitting ocean are found to 1) increase stratification and thus oppose the densification by northward Ekman flow and 2) increase subduction locally. These effects of eddies are not well reproduced by the eddy parameterization in the coarse-resolution ocean coupled model.

scholarly journals The North Pacific Climatology of Winter Mixed Layer and Mode Waters

2004 ◽  
Vol 34 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Toshio Suga ◽  
Kazunori Motoki ◽  
Yoshikazu Aoki ◽  
Alison M. Macdonald
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Mode Waters ◽  
The North ◽  
Winter Mixed Layer ◽  
The North Pacific

Formation and Subduction of Central Mode Water Based on Profiling Float Data, 2003–08

2011 ◽  
Vol 41 (1) ◽  
pp. 113-129 ◽  
Author(s):  
Eitarou Oka ◽  
Shinya Kouketsu ◽  
Katsuya Toyama ◽  
Kazuyuki Uehara ◽  
Taiyo Kobayashi ◽  
...  
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Large Scale ◽  
Kuroshio Extension ◽  
Subtropical Gyre ◽  
Late Winter ◽  
Mode Water ◽  
Central Mode Water ◽  
Winter Mixed Layer ◽  
Central Mode

Abstract Temperature and salinity data from Argo profiling floats in the North Pacific during 2003–08 have been analyzed to study the structure of winter mixed layer north of the Kuroshio Extension and the subsurface potential vorticity distribution in the subtropical gyre in relation to the formation and subduction of the central mode water (CMW). In late winter, two zonally elongated bands of deep mixed layer extend at 33°–39° and 39°–43°N, from the east coast of Japan to 160°W. These correspond to the formation region of the lighter variety of CMW (L-CMW) and that of the denser variety of CMW (D-CMW) and the recently identified transition region mode water (TRMW), respectively. In the western part of the L-CMW and D-CMW–TRMW formation regions west of 170°E, the winter mixed layer becomes deeper and lighter to the east (i.e., to the downstream). As a result, the formed mode water is reentrained into the mixed layer in the farther east in the following winter and modified to the lighter water and is thus unable to be subducted to the permanent pycnocline. In the eastern part of the formation regions between 170°E and 160°W, on the other hand, the winter mixed layer becomes shallower and lighter to the east. From these areas, the L-CMW with potential density of 25.7–26.2 kg m−3 and the D-CMW–TRMW (mostly the former) of 26.1–26.4 kg m−3 are subducted to the permanent pycnocline, and they are then advected anticyclonically in the subtropical gyre. These results imply that during the analysis period large-scale subduction to the permanent pycnocline occurs in the density range up to 26.4 kg m−3 in the open North Pacific, whereas the winter mixed layer density reaches the maximum of 26.6 kg m−3. This is supported by the vertical distribution of apparent oxygen utilization in a hydrographic section in the subtropical gyre.

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