Factors Controlling Seasonal Variability of Sea Level in the Western Gulf of Aden

Abstract

Daily means sea level has been computed from hourly observations at Aden and Djibouti for the period of 2011–2014 to study seasonal variability in sea level in the western Gulf of Aden. This variability is investigated against the following controlling factors: sea level pressure, wind, and steric sea level. Variability in sea level at Aden and Djibouti shows strong seasonality with higher sea level in winter and lower sea level in summer with a range up to about 35 cm. The high-frequency variability in sea level agrees with variability in pressure, especially during winter following normal inverse barometric relation. Cross-shore wind affects sea level variability in Djibouti more than that in Aden, while along-shore wind plays a significant role in sea level variability at Aden. Daily steric sea level for both stations play a significant role in seasonal sea level anomaly (SLA) variability. Both stations shows that strong signals are the annual and semiannual, while small frequencies are negligible in comparison. For Aden and Djibouti stations, steric sea level is the dominant factor with a determination coefficient (DC) of 0.73, and 0.71, respectively. Along-shore wind has the second higher contribution for Aden with (DC) of about 0.3. The cross-shore wind component has the second highest contribution on Djibouti SLA with a DC of about 0.3, while for Aden, this factor has no effect on SLA. Sea level pressure (SLP) contribution is clearly seen in short-period variability for both stations.