Baltic Sea

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Secondly, a cold, oxygen-rich inow in intermediate waters was captured in May 2006 in the Stolpe Channel and later in September of the same year in the EGB. Temporal means of the zonal velocity of two ADCPs, deployed between September and December 2006 at the outlet of the Stolpe Channel, reveal a separation of the water column, where the eastward ow at the northern side dominates depths between 65-71 m and depths of 52-71 m at the southern side of the channel. The layer above on the other hand shows a westward ow. The deep, mainly eastward ow exhibits uctuations of about 2-4 days. Hourly and daily volume transports estimated from ADCP measurements for this period agree well with modelled volume transports from the high spatial resolution (1 nautical mile) MOM4 model. All signicant peaks in estimated transports were also captured by modelled volume transports. The mean volume transport through the Stolpe Channel for estimated volumes is 0.75 ± 2.32 km 3 /d and slightly higher for modelled volumes 0.81 ± 3.15 km 3 /d, both are well correlated with R=0.79. In the Stolpe Channel the following mechanisms can be derived from correlations. The sea level is directly steered by the regional wind and surface waters in the same direction as the wind. The deep current is mainly steered by changes in the sea level and is counteracting to the surface ow, i.e. during winds from the west the deep currents travel towards west and during winds from the east currents travel eastwards. Although, in times of weak westerly winds deep eastward currents still prevail, but then originate from a geostrophic ow. Hence, observed pulse-like currents in the Stolpe Channel are partly driven by the regional wind, i.e. up to 50 % and partly driven by sloping density gradients of dense bottom waters and therefore resulting geostrophic currents. Comparisons of the wind's frequency spectrum with the frequency spectra of the along-slope current of the two ADCPs reveal that the 2-4 day long current uctuations originate from changes in the regional wind. Each of these uctuations transports a volume of around 1.78 ± 1.15 km 3 /d eastwards. These 2-4 day long uctuations transport nearly the same volume in a single event as the 3-monthly mean. iii
Contents Abstract Contents List of Figures List of Tables ii iv x xiii 1 Introduction 1 1.1 Investigations of spatiotemporal scales in the <strong>Baltic</strong> Proper . . . . . . . . . . . 1 1.2 Topography of deep <strong>Baltic</strong> basins . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Basic hydrography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 Pulsating inows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.5 Recent inow history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.6 Deep boundary currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.7 Methodical specics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2 Data and Methods 14 2.1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.1.1 MESODYN project 1997/98 . . . . . . . . . . . . . . . . . . . . . . . 14 2.1.2 RAGO project 2006/07 . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Analysis of observational data . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.1 Hydrographical data . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.2 Current records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2.3 Wind measurements and sea level gauges . . . . . . . . . . . . . . . . 19 2.3 Numerical model MOM4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 iv
Page 1 and 2: No 88 2012 Spatiotemporal Scales of
Page 3 and 4: Meereswissenschaftliche Berichte MA
Page 5: Abstract The Baltic Sea is surround
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 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
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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
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needs some explanation, since the l
Page 93 and 94:
and Fig. 4.24 and displayed in Tabl
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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
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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
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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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