The gulf is any of the coastal indentations i.e. any of the deep recess or notch on the edge of a coastline. Regardless of the size, depth, configuration and geologic structure the gulf coastal feature is an inward-pointing feature of the ocean. There is wide variation in the naming of the gulfs. Different names depending on the size of various gulf coastal regions used are bay, bight, firth, sound, and fjord. Many of these pronounced features around the oceanic margins have no name at all. This leads to some of the characteristics of such gulf coastal features also being applied to bays, and other similar geographical features as well.
Topographical Characteristics of Gulf Coastal Regions
Some of the features of a single gulf coastal region are formed along the linear shores of the continents. When there is any irregularity in the shoreline then there are high chances of formation of different small and complex geological features which can lead to the formation of groups of gulfs that may or may not be similar. Most of these features of the shorelines can have inward-facing coastal features which are also known as bays. This also leads to diversity in the topographic features of the Gulf coastal regions.
Along with the shapes, there is also much diversity in the bottom topography of the gulfs. The factors that contribute to the diversity are heavily influenced by the geological structure and development in the given region. Simple shapes and shallow depths are formed from homogenous bedrock of low strengths or resistance. An example of such a case is the Gulf of Riga in the Baltic Sea. At some places, the gulfs are in the form of long narrow arms giving almost parallel shores extending inwards. Such regions occupy the troughs that were created during a period of low sea level. On the other hand, deep angular gulfs are formed along with the features of fractures, faults and rifts having an irregular bottom topography. Some of the gulfs have extremely deep and narrow coastal features with parallel shores. Some of the fjord-gulfs are noted for their very high length-to-width ratios. Regions with non-uniform deformation and uplift form gulfs that are irregularly shaped and complicated having a distinct bottom topography as well.
The gulfs are usually connected to the sea via straits. There are gulfs where there is an archipelago at its mouth and some of the gulfs open into the sea or into other gulfs present on the opposite sides for which examples include the Gulf of Aden and Gulf of Oman.
Factors Affecting the Characteristics of the Gulfs
Gulfs can be different from the nearby ocean or sea, because of the water properties and dynamics, and sedimentation processes. The size and shape of a given gulf along with its depth and bottom topography determines the differences of the gulf with the nearby waterbody. These differences also depend on the degree of isolation of the gulf with the waterbody. The degree of isolation depends on the ratio of the mouth of the gulf to the total surface area of the gulf or the ratio of the cross-sectional area of the mouth to the total volume of the water. In the case of a submarine ridge or rise feature of the sill, the ratio of the depth above the sill to the depth of the gulf is of significance. But there hasn't been any comparisons in-between any such ratios and because of this, the variables that control the ratios are qualitative rather than quantitative.
The water exchange between the ocean and the gulf is hampered by the high sill leading to oxygen deficiency by stagnation like in the fjords of Norway, the Red Sea and the Black Sea. This is because the presence of the sill causes independent circulation of the gulf waters, which are generated by the local winds and the run-off of the rivers. Sills are usually dispensable for the formation of independent circulation. A narrow mouth like in the Gulf of Bothnia will lead to the same result. The water of the gulfs is freshened by the river runoff in humid climates. The salinity is low in the Gulf of the Baltic Sea along with the southern coast of the Kara Sea. The water only becomes fresh in the head especially in the spring when usually the snow begins to thaw. The arid zone of the gulfs suffer from intensive evaporation and some of it is received from the little river runoff. This makes the salinity increase in the climatic regime. In addition to this effect, the runoff delivers the organic matter and the nutrient salts that might determine the specific features of life in the gulfs. The organisms develop in quantities and belong to many different species and a number of genera. Hence, industries focused on shrimp, oyster and other fisheries got concentrated into the gulfs.
The formation of the gulfs and its geologic structure and development history is varied. Depending on the factors discussed above for the formation of the gulf. These factors allow some degree of classification. The following classification is based on some of these
A1: Areas with open concavities of the continental coast
A2: Large gulf areas isolated from the oceans
A3: Ocean gulfs that are isolated from the water bodies but to a lesser extent
B: Gulf features situated on the continental shelf
C1: Intercontinental gulf basins of the sea including the deepwater part
C2: Intercontinental gulfs with both deepwater and shelf gulf parts