In astronomical-geographic terms, a tide signifies the gravitational pull of the moon. Therefore this means that a high tide occurs when the alignment of the moon is closer to the earth and a low tide happens when the moon is positioned farther from the earth. Tides are the daily rise and fall of sea level at any given place. The pull of the Moon’s gravity on Earth is the primary cause of tides and the pull of the Sun’s gravity on Earth is the secondary cause The Moon has a greater effect because, although it is much smaller than the Sun, it is much closer. The Moon’s pull is about twice that of the Sun’s.Sun Every particle on Earth is pulled on by the gravity of the moon. Because liquids move more easily, the pull of gravity is much more noticeable in liquids than in solids.

The moon's pull is strongest on the part of the Earth directly facing the moon. When that part of the Earth happens to include an ocean, the water there bulges toward the moon. At the same time, water on the opposite side of the Earth bulges due to inertia caused by the motion of the Earth and moon around each other Two high tides and two low tides occur each day. The ocean is constantly cycling from high tide to low tide and then back to high tide. There is about 12 hours and 25 minutes between the two high tides.

Spring tide : tides with maximum daily tidal range that occur during the new and full moons and when the sun, Earth, and moon are in alignment with one another These are very strong tides and occur every 14 days. Neap Tides :The sun, Earth, and moon are at right angles during the moon’s two quarter phases. Neap tides which are very weak tides, occur during this time. During this time, the gravitational forces of the moon and sun are perpendicular to each other which cause the pulls to "cancel out" each other. The diagrams below show the two situations in which neap tides occur.Neap tides Neap Spring

CHART DATUM is a very important level, It is sometimes known as LAT (Lowest astronomical tide) lots of other levels are measured from it: - Drying heights (Land which covers and uncovers with the tide) Charted depths or soundings, are measured below Chart Datum. All tidal levels (MHWS, MHWN, MLWS, MLWN and the Height of tide). MHWS. Mean High Water Springs. MHWN. Mean High Water Neaps MLWS. Mean Low Water Springs MLWN. Mean Low Water Neaps Tidal Range is the difference in height between a particular High and low water. MHWS is an important level as all heights on land are measured from it. e.g. the height of a hill or a lighthouse.

when the tide is coming in we call it flooding, and when it’s going out it’s ebbing. Highest astronomical tide (HAT) – The highest tide which can be predicted to occur. Note that meteorological conditions may add extra height to the HAT. Mean high water springs (MHWS) – The average of the two high tides on the days of spring tides. Mean high water neaps (MHWN) – The average of the two high tides on the days of neap tides. Mean sea level (MSL) – This is the average sea level. The MSL is constant for any location over a long period. Mean low water neaps (MLWN) – The average of the two low tides on the days of neap tides. Mean low water springs (MLWS) – The average of the two low tides on the days of spring tide

Tide table standard port Red :Spring Blue : Neap

Climate affecting shipping According to the ap journal, recently, abnormal amounts of icebergs have drifted into north atlantic shipping lanes.

There are two type of Ocean Currents: 1. Surface Currents--Surface Circulation These waters make up about 10% of all the water in the ocean.These waters are the upper 400 meters of the ocean. Deep Water Currents--Thermohaline Circulation These waters make up the other 90% of the ocean These waters move around the ocean basins by density driven forces and gravity. The density difference is a function of different temperatures and salinity These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase. Primary Forces--start the water moving The primary forces are: 1. Solar Heating 2. Winds 3. Gravity 4. Coriolis Solar heating cause water to expand. Near the equator the water is about 8 centimeters high than in middle latitudes. This cause a very slight slope and water wants to flow down the slope. Winds blowing on the surface of the ocean push the water. Friction is the coupling between the wind and the water's surface. A wind blowing for 10 hours across the ocean will cause the surface waters to flow at about 2% of the wind speed.Water will pile up in the direction the wind is blowing.

Gravity will tend to pull the water down the "hill" or pile of water against the pressure gradient. Coriolis Force intervenes and cause the water to move to the right (in the northern hemisphere) around the mound of water. These large mounds of water and the flow around them are called Gyres. The produce large circular currents in all the ocean basins.

If each time zone were one hour apart, each one should theoretically be 15 degrees wide on a map, resulting in a total of 24 worldwide. However, there are also several time zones with offsets that are only 30 and 45-minutes apart, making the total number of time zones much higher30 and 45-minutestotal number of time zones