Tuvalu - Funafuti 2021 Tide Predictions Calendar Climate and Oceans Support Program in the Pacific
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Tuvalu - Funafuti 2021 Tide Predictions Calendar Climate and Oceans Support Program in the Pacific A Pacific Islands Program supported by the Australian Government Tuvalu - Funafuti Paara Fualefeke Mulitefala Te Afualiku Amatuku Tengako Tepuka Tide Gauge Location Fualopa Fualopa Fuafatu Fongafale Te Namo Fatato Vasafua Funamanu Papa Elise Fuagea Fale Fatu Tefala Mateiko Falaolgo Funafala FUNAFUTI Tutanga Tengasu Tefota Teafuafou Telele Awalau Motuloa Motugie Meteorological and seasonal effects 10 highest tides for 2021 10 lowest tides for 2021 Tide predictions are based on the effects Date Time Height (m) Date Time Height (m) of the gravitational forces exerted by the 28-Apr 5:30 3.21 5-Nov 23:22 1.02 moon, the sun, and the rotation of the earth, as well as average seasonal changes. 29-Mar 17:31 3.2 24-Jul 11:24 1.03 The actual tide height will be a combination 27-Apr 4:49 3.19 4-Dec 23:13 1.03 of these effects and the weather conditions 28-May 16:52 3.19 25-Jun 11:33 1.04 at the time. The effects of the weather are not included in tide predictions. 28-Feb 17:53 3.19 27-May 11:39 1.04 30-Mar 5:53 3.18 4-Nov 22:38 1.04 4-Dec 16:46 3.18 26-May 10:50 1.04 5-Nov 17:01 3.17 7-Oct 11:15 1.04 Map courtesy of the Pacific Community. Some rights reserved. 27-Feb 17:15 3.17 27-Apr 11:04 1.05 Front cover photo courtesy of Gary Lee. 5-Dec 17:34 3.15 25-Jul 12:07 1.05 Some rights reserved. Tides and Extreme Tide Events What causes tides? What are king tides? Tides are the daily rise and fall of sea levels, caused The term king tide is commonly used to describe an mainly by the gravitational pull of the moon as it revolves especially high spring tide. King tides occur a few times around the earth. Tides are also affected by the earth’s every year, when the gravitational pull of the sun and rotation and the gravitational pull of the sun. moon upon the earth is strongest. This happens when the moon is closest to the earth in its monthly orbit. When this coincides with a spring tide, it will produce an especially high tide, or king tide. In the Pacific, the highest king tides often occur during the months from November to March, when the earth is also closest to the sun in its annual orbit. What do I need to know about king tides? King tides are a natural part of the tidal cycle and are Figure 1. Low and high tide in Suva, Fiji. Photo: Molly Powers-Tora (201 8). predictable. A king tide can cause coastal flooding, even on a clear, sunny day. What are spring tides and neap tides? When king tides coincide with cyclones, floods or storms, water levels can rise significantly, potentially Spring and neap tides are part of the normal tidal cycle causing damage to property and the coastline. The and occur regularly, usually twice per month. actual height reached by a king tide will depend on the Spring tides are very high tides and very low tides that local weather and ocean conditions on the day. occur during full and new moon phases, when the It is also important to know that king tides have always gravitational forces of the sun and moon combine to occurred and are not a result of sea level rise. exert a stronger pull on the oceans. During the moon’s quarter phases each month, the sun and moon are at right angles, and the gravitational forces cancel each other out, resulting in lower high tides and higher low tides called neap tides. Figure 3. Strong southeasterly winds and currents combine to create higher than normal tides in Levuka, Fiji. Photo: Molly Powers-Tora (2013). Figure 2. Spring and neap tides occur every month and correspond with the phases of the moon. Source: www.moononly.com Climate and Oceans Support program in the Pacific Tides and Extreme Tide Events How are tides predicted? Why are some tides higher or lower The time and approximate heights of tides are very than predicted? predictable. They follow the laws of physics and can be Tide levels can vary from predicted levels for a number of calculated with mathematical formulas. reasons, including: By observing and recording tides at a single location over 1. Geography: The shape of bays and other coastal many years, we can gain a better understanding of tides geography can magnify or otherwise influence water and sea level changes over time. levels. The Pacific Sea Level and Geodetic Monitoring Project 2. Weather: Wind speed and direction, air temperature, has been recording sea level and weather statistics at barometric pressure and other weather conditions can 13 Pacific countries for more than 25 years. greatly affect water levels. These observations tell a story about the sea levels at 3. Waves: Both nearby and faraway events such as these locations, such as: How high was the highest tide storms, landslides and earthquakes can create large in Apia? What effect does El Niño have on sea levels in waves that lead to coastal flooding. Kiribati? All of this information is also used to verify and 4. Climate drivers: El Niño or La Niña conditions in the improve tide predictions. Pacific can raise or lower sea level by as much as 50 cm. 5. Sea-level rise: Through assessing observations and research, the Intergovernmental Panel on Climate Change (IPCC) concluded that global average sea levels have been rising at a rate of about 3 mm per year since 1993. Levels were 225 mm higher in 2012 compared to 1880. Sea-level rise can contribute to higher tides, but the rates are not the same at all locations. Figure 4. Technicians working on the recently-refurbished Cook Figure 5. Predicted vs actual sea level at the Apia tide gauge Islands tide gauge, which has been monitoring sea level and Samoa, 3 May 2018. weather conditions in Rarotonga for over 25 years. Photo: Stamy Criticos (2012). The Pacific Sea Level and Geodetic Monitoring Project provides sea level and meteorological information for 13 countries and tide predictions for 20 locations in the Pacific region. It is an important resource for those involved in disaster mitigation and adaptation planning, coastal development, and the shipping, fishing and tourism industries. To access tide calendars, wave and weather maps, and climate data for your location visit: www.bom.gov.au/pacific/index.shtml For Real-Time Display of tide gauge data, visit: http://www.bom.gov.au/cosppac/rtdd/q1c7o0hj48yu/ © Commonwealth of Australia 2014 0047 1.08 0134 1.08 0220 1.09 6 0635 0.56 7 0724 0.57 8 0815 0.57 9 1248 1.14 1337 1.13 1425 1.12 Tides and Sea Level 1919for 0.50 Coastal2006 0.50 2051 0.51 1.5m Development and1m Safe Navigation 0.5m What is a Tide Datum? 0 6 12 18 0 6 12 18 0 6 12 18 0 A Tide Datum is a fixed level against which sea level 0552 1.23 0020 0.45 0114 0.42 can be measured in a given location. A tide station 13 1212 0.44 14 0642 1.28 15 0733 1.33 16 datum was established when the sea level monitoring 1815 1.19 1304 0.38 1400 0.34 1908 1.21 2003 1.23 station featured in this calendar was first installed. The MSL tide predictions in this calendar are all relative to Tide Prediction Datum. 1.5m NEAP RANGE SPRING RANGE Why do we need a Tide Datum? 1m Tide records must be referenced to a common datum 0.5m to ensure consistency. This is important if the tide CHARTED CD DEPTH gauges are moved or in the event they are damaged or 0 6 12 18 0 6 12 18 0 6 12 18 0 destroyed. In this case, tide readings from replacement gauges can be referenced to the same datum as Figure 1. How0000 does THIS............. 1.24 relate0100 to THIS? 1.24 0158 1.24 before and continue to contribute to our understanding 20 0603 0.40 21 0704 0.41 22 0805 0.42 23 of tides. 1220 1.32 1321 1.29 1423 1.27 1846 0.31 1945 0.33 2043 0.35 What is the relationship between tides 1.5mand sea level? 1mWhen the range of highest and lowest tides are averaged over a long period (usually at least 19 years), we can establish 0.5mMean Sea Level. Mean Sea Level (MSL) is an important reference level, as all heights on land are measured in metres or 0feet above 6 12 mean18 sea level 0 as 6 in Figu12 re 182. 0 6 12 18 0 All sea level monitoring stations are tide gauges, but not all 0007 0.44 0054 0.46 0139 0.47 tide 27gauges 0625can accurately 1.24 28 measu0711re changes 1.24 in 29sea level.0755 1.22 30 The Pacific 1248Sea Level 0.41 and Geodetic1336 Monitoring 0.41 stations1422 0.40 include specialised1857 1.16weather, ocean,1943 and 1.13land monitoring2027 1.11 sensors that have been operating since 1991, allowing us to measure the extent to which sea level is affected by natural 1.5m Figure 2. An elevation sign from Tarawa, Kiribati variability and man-made climate change at those locations. Photo: Wandering Ken, 2011.