Baltic Sea

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advective and diusive uxes at the sediment-water interface. Dening the volume-averaged salinity, 〈S〉 V = 1 V ∫ V S dV , (3.4) the salinity budget, (3.3), can be re-written without further assumptions as an expression for the area-averaged turbulent salt ux across A t , ¯F S = V A t ( ¯SI − ¯S O T R − d〈S〉 V dt ) , (3.5) where T R = V/Q denotes the formal residence time determined by the overall ux, Q, of water entering the control volume through A t with upward velocities w < 0. ¯SI and ¯S O , respectively, denote the transport-weighted average salinities of inowing (I) and outgoing (O) waters. Hence, the turbulent salt ux can be estimated from the evolution of the average salinity inside the control volume, and the properties of incoming and outgoing advective uxes. Equation (3.5) can be also developed for potential temperature, as well as for any other scalar quantity with negligible sediment uxes and internal sources. On the other hand, it becomes clear that any advective uxes aecting (3.5) will, in general, not be known. Nevertheless this equation is still useful to obtain minimum values for the vertical uxes and diusivities under certain conditions. One of them is given by the fact that below the enclosing isobath of 170 m the deep water renewal is driven by dense saline gravity currents. Associated saline intrusions enter the control volume as a volume ux, Q, across the level surface, A t , with high salinity, ¯SI , causing upwelling of an equal ux, Q, of low-salinity water at other locations due to continuity. This scenario implies that the rst term on the right-hand side of (3.5) will be positive. In situations where the rate term on the right-hand side of (3.5) is negative, i.e. where deep water renewal by advection is weak but not necessarily negligible compared to vertical mixing, expression (3.5) yields ∂S ¯F S = −¯κ S ∂z ≥ − V d〈S〉 V A t dt , (3.6) corresponding to lower bounds for the averaged ux, ¯FS , and the average vertical diusivity, ¯κ S , at z = z t . Note that ¯κ S is only implicitly dened by the rst equality in (3.6), and by the way the averaged vertical gradient, ∂S/∂z, is computed.Interestingly, for so-called warm inow events, as observed here, incoming waters are characterised by high salinities and high temperatures, such that identical arguments lead to lower bounds, analogous to (3.6), for the potential temperature ux, ¯Fθ , and diusivity, ¯κ θ . 38
190 a 200 Depth (m) 210 220 230 240 6.5 6.6 6.7 6.8 6.9 7 7.1 7.2 7.3 pot. Temperature ( o C) 17.02.98 18:07 17.02.98 20:49 190 200 18.02.98 7:09 17.2.98 mean prof. 27.03.98 1:20 21.4.98 14:57 b Depth (m) 210 220 230 240 12.25 12.3 12.35 12.4 12.45 12.5 12.55 12.6 12.65 12.7 Salinity (g/kg) Figure 3.10: (a) Potential Temperature vs. depth, (b) salinity vs. depth of BMP271 on 17-18 February 1998, 17 February 1998 (mean prole), 27 March 1998 and 21 April 1998. Sampling time given as dd.mm.yy HH:MM UTC. Diamonds represent the corresponding potential temperature and salinity averages of the basin's volume between 225-235 m. The rate term appearing in (3.6) was estimated from nite dierencing the volume average, 〈S〉 V , at three dierent dates starting on 17 February 1998 (see Table 3.3). CTD-proles taken near the centre of the basin (Fig. 3.7) illustrate that after a strong increase of bottom temperatures during the warm inow event, all near-bottom temperatures and salinities (compare Fig. 3.10 b) following 17 February 1998 continuously decreased. This indicates that by this date bottom-water renewal by advection is no longer the dominating process such that the necessary conditions for the applicability of (3.6) are satised. Using the regression in equation 4.10 suggested by Hagen and Feistel (2001), the volume-averaged salinities at the dates shown in Table 3.3 were estimated from salinity proles taken at the central monitoring station 39
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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 and 36: whereas the length of the NE time s
Page 37 and 38: have a thickness of only 1.5 m in o
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: Date 31.8.1997, 03.11.1997, 03.11.1
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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