 |
| Titel |
The Importance of Synchronized Observations in Coastal Seas with Large Intra-Tidal Temperature Variation and Intermittent Thermocline |
| VerfasserIn |
G. L. Liu, Z. Liu, H. W. Gao |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058543
|
|
|
|
|
|
| Zusammenfassung |
| In coastal seas, the combination of influences from multiple forcing (e.g. tide, wind and
river), the presence of complex topography and coastline, the coupling of multiple process
coupling (e.g. stratification, air-sea heat exchange), and other factors often leads to strong
variability of sea state. To demonstrate the importance of synchronized observations for
synoptic description of sea state, a 21-vessel synchronized biogeochemical observation was
carried out from Aug 17th to 20th 2009 in Jiaozhou Bay (JZB) of China with a surface area
of about 400km2. The observation provides high spatial and temporal resolution
synchronized thermohaline data. The stations are positioned approximately 20 km2 apart with
at least 0.5m in depth. Continuous sampling was carried out in the shallow northern region
with depth under 10m. The interval of profiles was one hour in regions deeper than 10m. We
preliminarily analyzed the intra-tidal variation of seawater temperature structure and the first
observed intermittent thermocline in JZB in summer. The maximum intra-tidal variation of
seawater temperature can reach as high as 2.0Ë C in JZB. Empirical Orthogonal
Function (EOF) analysis shows that tide plays a key role in the intra-tidal variation; the
seawater temperature shows obvious semidiurnal period and is out of phase with the
elevation. The warm seawater temperature in the northern shallow region is about 2.0Ë
C higher than that in the southern deep region. In addition, the topography and
coastline significantly affect the seawater movement and consequently shape the
horizontal distribution of temperature, which is characterized by a varying range of
cold water near the bay mouth. The stratification is weak in the northern shallow
region and near the bay mouth due to the strong mixing of tide and wind. However,
in the freshwater influenced southern deep region (>8m), thermocline can form
(usually lasts for 2 to 3 hours) when tidal currents are small. Thermocline may
occur under the combined effect of stratification as a result of lighter warm water
transported over the heavier cold water by the vertical gradient of tidal current and weak
tidal stirring. The results demonstrate that in coastal regions with large intra-tidal
variation of sea temperature and intermittent thermocline such as the tide-dominated
Jiaozhou Bay, it is necessary to carry out synchronized observations in order to
depict and forecast the synoptic conditions of sea state and its short term change. |
|
|
|
|
|
|