An analysis of drivers of seawater temperature in Kuwait Bay, Arabian Gulf

Abstract

Kuwait Bay presents a unique ecosystem and a significant nursery ground for many fish and shrimp species. In the last three decades, the bay has been under pressure from urbanization as well as from development from the entire region of the Arabian Gulf. Seawater temperature has an important impact on the marine environment. The aim of this study is to evaluate the drivers of seawater temperature in Kuwait Bay over the last two decades. Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat satellites images were used to describe the spatial and temporal distribution of sea surface temperature (SST) in the Arabian Gulf and Kuwait Bay. Hourly temperature measurements collected during the winter, 2007 and summer, 2008 were used to define the vertical temperature gradient in the water column, sea-bed and the intertidal flats of Kuwait Bay. Advanced Very High Resolution Radiometric (AVHRR) satellite data collected between 1985 and 2007 was also used to study the trends and drivers of increasing SST in Kuwait Bay over the last two decades.

Satellite imaging showed that generally SST of Kuwait Bay is higher in the south than in the north. Highest SST was recorded near local human activities especially close to power and desalination plants due to thermal discharges. The field measurements showed that the water temperature is well-mixed in the bay. Seawater temperature reached 37 ºC in summer and dropped to 15.2 ºC in winter. Measurements beneath the sea-bed and within the intertidal flats showed that the temperature increased with depth in winter and decreased in summer. In winter, the sea-bed and intertidal flats are a source of heat to the water column, during summer the opposite is true. AVHRR data showed that the seawater temperature increased in Kuwait Bay by 0.62 (± 0.01)ºC/decade in the last two decades. This trend is three times greater than the global average. The defined trends were substantiated by routine in situ monthly measurements of SST made by the EPA in the bay, and were also similar in pattern and trend to air temperature recorded at Kuwait airport. Temperature trends have been affected by drivers, conveniently sub-divided into global (which contributes 37% of the change), regional (which contributes 50% of the change) and local (which contributes 13% of the change). SST measurements showed peaks in summer temperature coincident with El Niño events in 1998 and 2003. The measurements also showed a relatively-low summertime peak during 1991 in the aftermath of Iraqi invasion of Kuwait due to atmospheric dimming brought about by dense smoke that persisted in the region for most of that year. The long term trend also showed a drop in temperature after 2004 as a result of increasing dust storm frequency in the region. Air temperature was found to be the most dominant driver of seawater temperature in Kuwait Bay and operates at a regional scale. At the local scale the seawater temperature of Kuwait Bay is influenced by intertidal flat exposure time and the thermal discharge from power and desalination plants.

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