Baltic Sea

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advection and mixing schemes, which are continuously improved by contributions of the user group. The MOM code is fully documented in a detailed manual, see Griffies et al. (2004). Examples of MOM based model simulations for the Baltic Sea are summarised in Schmidt et al. (2008). 2.3.1 Model specications The model data utilised for this study rely on a simulation of the Baltic Sea which is based on the code version MOM-4. Essential features of the MOM adaptation for the Baltic Sea at IOW are: • High resolution digital Baltic bathymetry of Seifert et al. (2001), • A tracer conserving treatment of fresh water uxes, see Griffies et al. (2001), • An atmospheric boundary layer module, computing air-sea uxes of heat and momentum from standard weather model data (wind, air pressures, air temperature, humidity and cloudiness), • Coupling of salinity and water temperature at the open boundary in Skagerrak to monthly climatological means derived from Janssen et al. (1999); the sea level is prescribed according to sea level gauge observations at Kungsvik provided by Swedish Meteorological-Hydrological Institute (SMHI, Norrköping), • Average monthly discharge of fresh water by rivers derived from Bergström and Carlsson (1993) and adapted to the total yearly runo which is continuously updated by HELCOM (2009). The model conguration is illustrated in Fig. 2.1. The model comprises the whole Baltic Sea between 9 ◦ 20 ′ − 15 ◦ 20 ′ E and 53 ◦ 50 ′ − 56 ◦ 20 ′ N with a regular grid referring to a spherical earth of 6371 km radius. The horizontal grid spacing of 1 minute with respect to geographical longitude and 2 minutes in longitude corresponds to a horizontal resolution of 1 nautical mile or 2 km, respectively. The horizontal grid is of the so-called B-type, thus grid points of current components (u, v) are half a grid step staggered against the grid points where scalar quantities, like temperature and salinity, are set-up. Vertically, the water body is divided into 77 layers of prescribed thickness (geopotential or z-coordinates). For the upper 27 m, layers 20
have a thickness of only 1.5 m in order to resolve the shallow sills in the southwestern Baltic Sea. Below 27 m, the layer thickness is smoothly stretched to 5 m to a maximum depth of 268 m. At the sea bottom partial grid cells of at least 0.5 m thickness are applied to approximate topographic slopes. The undisturbed surface layer has a thickness of 2.6 m which allows realistic sea level variations of up to approximately ±1.5 m. Such a high vertical and horizontal resolution is needed to resolve the processes relevant in the Baltic Sea, since the long-term thermohaline circulation is dependent on various short-term events like minor and major inows, drifting eddies and coastal jets. The spatial scale of these processes is small in comparison with the horizontal scale of the sub-basins and channels, the baroclinic Rossby radius is in the order of only 1 − 7 km (Fennel et al., 1991), small in comparison with the horizontal scale of the sub-basins and channels. Vertical mixing processes are modelled by the k-prole parameterisation (KPP), a non-local scheme described in detail by Large et al. (1994), whereas horizontal mixing and viscosity are calculated from current shear using a Smagorinski scheme, see Smagorinsky (1963), Smagorinsky (1993) and Griffies and Hallberg (2000). The meteorological forcing of the Baltic Sea MOM4 simulations is provided by the Deutscher Wetterdienst (DWD, German Weather service) running the regional model COSMO-EU 3 (formerly known as DWD/LME) which covers the whole European region with a grid spacing of 7 km. Output from the operational forecasts at 3 − 15 hours is archived twice daily at IOW with a time resolution of 3 hours. Air-sea uxes of mass, momentum and energy are calculated from air pressure, air temperature, dew point temperature, wind, precipitation, cloudiness, and downward short wave and long wave at the sea surface according to standard parameterisations taken from Beljaars (1995). 2.3.2 Model data Because of its high resolution the Baltic model requires high computation and storage capacity. The simulations are carried out on the high-performance parallel computers of Norddeutscher Verbund für Hoch- und Höchstleistungsrechnen (HLRN) at Berlin and Hannover. The model runs (in time slices of 30 days) are nished with storage of a restart snapshot. Full 3D model elds are saved as 5-day averages since every parameter requires 140 MB per time step. 3http://www.cosmo-model.org/content/tasks/operational/dwd/default_eu.htm 21
Page 1 and 2: No 88 2012 Spatiotemporal Scales of
Page 3 and 4: Meereswissenschaftliche Berichte MA
Page 5 and 6: Abstract The Baltic Sea is surround
Page 7 and 8: Contents Abstract Contents List of
Page 9 and 10: Acknowledgement 109 Appendix 111 vi
Page 11 and 12: M-7/M-8 Mesodyn hydrographic snapsh
Page 13 and 14: List of Figures 1.1 Baltic Sea - ba
Page 15 and 16: 4.32 Regression sea level dierence
Page 17 and 18: 1. Introduction 1.1 Investigations
Page 19 and 20: circulation above topographic anks
Page 21 and 22: 58 o N 190 230 210 100 75 100 100 7
Page 23 and 24: y 'new' deep water. For instance, i
Page 25 and 26: events. During and after such event
Page 27 and 28: this inow event was classied as 'mo
Page 29 and 30: Scale (PSS-78), roughly by 0.5%, as
Page 31 and 32: (Acoustic Doppler Current Proler) a
Page 33 and 34: for the southernmost zonal section
Page 35: whereas the length of the NE time s
Page 39 and 40: dependent salt volumes for the deep
Page 41 and 42: 7 6.5 a Temperature ( o C) 6 5.5 5
Page 43 and 44: Potential Temperature ( o C) 8 7 6
Page 45 and 46: inowing waters masses with variable
Page 47 and 48: following these bounds will be used
Page 49 and 50: 60 80 100 −45 −50 −55 Pressur
Page 51 and 52: Monitoring Station BMP271 60 80 100
Page 53 and 54: Date 31.8.1997, 03.11.1997, 03.11.1
Page 55 and 56: 190 a 200 Depth (m) 210 220 230 240
Page 57 and 58: Date (ID) 〈S〉 V (g/kg) 〈θ〉
Page 59 and 60: deviation of the temperature uctuat
Page 61 and 62: 4. The Deep Circulation in the EGB
Page 63 and 64: Depth (m) 50 100 150 200 17 16 4.6
Page 65 and 66: For this reason, the displayed temp
Page 67 and 68: 6.4 6.3 178 m 208 m 223 m Daily Tem
Page 69 and 70: The deep parts of the basin are exp
Page 71 and 72: On the 29 September 2006 between 60
Page 73 and 74: In the geostrophic balance horizont
Page 75 and 76: captured eastward velocities up to
Page 77 and 78: Figure 4.11: Modelled current veloc
Page 79 and 80: SFS and SFN. At the southern ank a
Page 81 and 82: Mean Volume Transports Mean Volume
Page 83 and 84: 160 170 180 Volume of EGB below 170
Page 85 and 86: Basin 55.9 ◦ N. From there the bo
Page 87 and 88:
Volume transports (km 3 /d) 15 10 5
Page 89 and 90:
Gdansk Basin happened a few weeks e
Page 91 and 92:
needs some explanation, since the l
Page 93 and 94:
and Fig. 4.24 and displayed in Tabl
Page 95 and 96:
Salt (t) 8 6 4 2 0 2 4 6 8 x 10 10
Page 97 and 98:
Time Period Stolpe Channel at 17.5
Page 99 and 100:
Modelled volume transport through S
Page 101 and 102:
discovered that most of the varianc
Page 103 and 104:
to the right (perpendicular) to the
Page 105 and 106:
of salty and often well oxygenated
Page 107 and 108:
Depth (m) 40 45 50 55 60 4 3 2 1 0
Page 109 and 110:
a correlation coecient of R=-0.68 a
Page 111 and 112:
5. Discussion and Conclusions 5.1 D
Page 113 and 114:
graphic cross-sections, conducted i
Page 115 and 116:
direction as the wind. The deep lay
Page 117 and 118:
Bibliography Axell, L. B., 1998: On
Page 119 and 120:
Griffies, S. M., R. C. Pacanowski,
Page 121 and 122:
Matthäus, W., 1993: Major inows of
Page 123 and 124:
Rubio, A., D. Gomis, G. Jordà and
Page 125 and 126:
Zhurbas, V., I. Oh and V. Paka, 200
Page 127 and 128:
Appendix Current speed and directio
Page 129 and 130:
Current speed and direction (cm/s)
Page 131 and 132:
2 1.5 1 Cumulative volume through S
Page 133 and 134:
Volume (km 3 ) 2.5 2 1.5 1 0.5 0
Page 135 and 136:
10 3 Regional Wind 7 Power Spectra
Page 137 and 138:
NE along−slope at 178m 10 2 10 1
Page 139 and 140:
Meereswissenschaftliche Berichte MA
Page 141 and 142:
26 (1997) Lakaschus, Sönke: Konzen
Page 143 and 144:
51 (2002) Wasmund, Norbert; Pollehn
Page 145 and 146:
78 (2009) Wasmund, Norbert; Pollehn
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Baltic Sea

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