scholarly journals Internal Variability Role on Estimating Sea Level Acceleration in Fremantle Tide Gauge Station

2021 ◽  
Vol 9 ◽  
Author(s):  
Armin Agha Karimi
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Low Frequency ◽  
Internal Variability ◽  
Climate Indices ◽  
Level Variation ◽  
Sea Level Variation ◽  
Gauge Station ◽  
Trajectory Models

Low frequency internal signals bring challenges to signify the role of anthropogenic factors in sea level rise and to attain a certain accuracy in trend and acceleration estimations. Due to both spatially and temporally poor coverage of the relevant data sets, identification of internal variability patterns is not straightforward. In this study, the identification and the role of low frequency internal variability (decadal and multidecadal) in sea level change of Fremantle tide gauge station is analyzed using two climate indices, Pacific Decadal Oscillation (PDO) and Tripole Interdecadal Pacific Oscillation (TPI). It is shown that the multidecadal sea level variability is anticorrelated with corresponding components of climate indices in the Pacific Ocean, with correlation coefficients of −0.9 and −0.76 for TPI and PDO, respectively. The correlations are comparatively low on decadal time scale, −0.5 for both indices. This shows that internal variability on decadal and multidecadal scales affects the sea level variation in Fremantle unequally and thus, separate terms are required in trajectory models. To estimate trend and acceleration in Fremantle, three trajectory models are tested. The first model is a simple second-degree polynomial comprising trend and acceleration terms. Low passed PDO, representing decadal and interdecadal variabilities in Pacific Ocean, added to the first model to form the second model. For the third model, decomposed signals of decadal and multidecadal variability of TPI are added to the first model. In overall, TPI represents the low frequency internal variability slightly better than PDO for sea level variation in Fremantle. Although the estimated trends do not change significantly, the estimated accelerations varies for the three models. The accelerations estimated from the first and second models are statistically insignificant, 0.006 ± 0.012 mm yr−2 and 0.01 ± 0.01 mm yr−2, respectively, while this figure for the third model is 0.018 ± 0.011 mm yr−2. The outcome exemplifies the importance of modelling low frequency internal variability in acceleration estimations for sea level rise in regional scale.

Multidecadal internal variability role in estimating sea level acceleration: Fremantle case study

2021 ◽  
Author(s):  
Armin Agha Karimi
Keyword(s):  
Pacific Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
Low Frequency ◽  
Internal Variability ◽  
Anthropogenic Factors ◽  
Climate Indices ◽  
The Third ◽  
Trajectory Models

<p>Low frequency internal signals bring challenges to signify the role of anthropogenic factors in sea level rise and to attain a certain accuracy in trend and acceleration estimations; thus, modelling these signals is crucial. Due to both spatially and temporally poor coverage of the relevant data sets, identification of internal variability patterns is not straightforward. In this study, the identification and role of low frequency internal variability (decadal and multidecadal) in sea level change of Fremantle tide gauge station is analysed using two climate indices, Pacific Decadal Oscillation (PDO) and Tripole Interdecadal Pacific Oscillation (TPO). The wavelet transform is applied on the sea level and climate indices time series for this purpose. It is shown that the multidecadal sea level variability is anticorrelated with corresponding components of climate indices in the Pacific Ocean, with correlation coefficients of -0.9 and -0.76 for TPO and PDO, respectively. The correlations are comparatively low in decadal time scale, by correlation coefficient of approximately -0.5 for both indices. To estimate trend and acceleration in Fremantle, three trajectory models are tested. The first model is a simple second-degree polynomial comprising trend and acceleration terms. Low passed PDO, representing decadal and interdecadal variabilities in Pacific Ocean, is added to the first model to form the second model. For the third model, decomposed signals of decadal and multidecadal variability of TPO are added to the first model. For all trajectory models, different noise models are tried and according to Akaike and Bayesian information criteria, the best noise model is AR(5). In overall, TPO explains the low frequency internal variability better than PDO for sea level variation in Fremantle. Although the estimated trends does not change significantly for the three models, the estimated acceleration is substantially different. The accelerations estimated from the first and second models are statistically insignificant, 0.006 ± 0.012 mm.yr<sup>-2</sup> and 0.01 ± 0.01 mm.yr<sup>-2</sup> respectively, while this figure for the third model is 0.018 ± 0.01 mm.yr<sup>-2</sup>. The outcome exemplifies the importance of modelling low frequency internal variability in acceleration estimations for sea level rise in regional scale.</p>

Sea Level Variation around Australia and Its Relation to Climate Indices

2019 ◽  
Vol 42 (5) ◽  
pp. 469-489 ◽  
Author(s):  
Armin Agha Karimi ◽  
Xiaoli Deng ◽  
Ole Baltazar Andersen
Keyword(s):  
Sea Level ◽  
Climate Indices ◽  
Level Variation ◽  
Sea Level Variation

scholarly journals SEA LEVEL VARIATION AND GEOSTROPHIC CURRENT OF THE SUNDA STRAIT BASED ON TIDAL AND WIND DATA IN YEAR 2008

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Resni Oktavia ◽  
John Iskandar Pariwono ◽  
Parluhutan Manurung
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Tide Gauge ◽  
High Tide ◽  
Level Variation ◽  
Tidal Forces ◽  
Sea Level Variation ◽  
The Indian Ocean ◽  
Java Sea ◽  
Current Flows

<p>Sea level variation from four tide-gauge data in the Sunda Strait, Indonesia, in the year 2008 has been studied by using Wavelet 1 D Daubechius 1 level 5 type and Fast Fourier Transform methods. The hourly sea level variation in April and November (representing transitional seasonal conditions) is approximately +0.49 m; whereas in January (representing Northwest Monsoon condition) and July (representing Southeast Monsoon condition) can reach up to -0.48 m. In 2008, sea level variation in the Sunda Strait is mainly influenced by the monsoon. Results from this study show that there are at least three phenomena of sea level variations in the Sunda Strait, namely (1) seasonal variation (periodicity between 4-6 months) where it is believed influenced by the Java Sea; (2) intra-seasonal (periodicity between 1-3 months), which is more influenced by the Indian Ocean; and (3) tidal forcing (periodicity between 14-17 days, suggesting fortnightly tidal forces) which propagates from the Indian Ocean into the Sunda Strait. Result from surface geostrophic approximation calculation suggests that during Southeast Monsoon (June-August), monthly mean current flows southwestwardly towards the Indian Ocean with a velocity of 0.14-0.16 m/s. Whereas during Northwest monsoon (December-February), current flows northeastwardly towards the Java Sea with a velocity of 0.14-0.17 m/s. Furthermore, on the daily time scale, tidal current in the Sunda Strait flows into the Java Sea (Indian Ocean) during high tide (low tide) with a velocity ranging from 0.51 to 0.72 m/s (0.48 to 0.51 m/s).</p><p>Keywords: sea level variation, geostrophic approximation, tides, monsoon, Sunda Strait</p>

scholarly journals Low-frequency sea level variation and its correlation with climate events in the Pacific

2012 ◽  
Vol 57 (27) ◽  
pp. 3623-3630 ◽  
Author(s):  
TaoYong Jin ◽  
JianCheng Li ◽  
WeiPing Jiang ◽  
YongHai Chu
Keyword(s):  
Sea Level ◽  
Low Frequency ◽  
Level Variation ◽  
Sea Level Variation ◽  
The Pacific ◽  
Climate Events

scholarly journals THE IMPACT OF SEA LEVEL RISE ON GEODETIC VERTICAL DATUM OF PENINSULAR MALAYSIA

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 237-245 ◽  
Author(s):  
A. H. M. Din ◽  
I. C. Abazu ◽  
M. F. Pa’suya ◽  
K. M. Omar ◽  
A. I. A. Hamid
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Peninsular Malaysia ◽  
Level Variation ◽  
Sea Level Variation ◽  
Vertical Datum ◽  
Tidal Data ◽  
The Government ◽  
The Impact

Sea level rise is rapidly turning into major issues among our community and all levels of the government are working to develop responses to ensure these matters are given the uttermost attention in all facets of planning. It is more interesting to understand and investigate the present day sea level variation due its potential impact, particularly on our national geodetic vertical datum. To determine present day sea level variation, it is vital to consider both in-situ tide gauge and remote sensing measurements. This study presents an effort to quantify the sea level rise rate and magnitude over Peninsular Malaysia using tide gauge and multi-mission satellite altimeter. The time periods taken for both techniques are 32 years (from 1984 to 2015) for tidal data and 23 years (from 1993 to 2015) for altimetry data. Subsequently, the impact of sea level rise on Peninsular Malaysia Geodetic Vertical Datum (PMGVD) is evaluated in this study. the difference between MSL computed from 10 years (1984 – 1993) and 32 years (1984 – 2015) tidal data at Port Kelang showed that the increment of sea level is about 27mm. The computed magnitude showed an estimate of the long-term effect a change in MSL has on the geodetic vertical datum of Port Kelang tide gauge station. This will help give a new insight on the establishment of national geodetic vertical datum based on mean sea level data. Besides, this information can be used for a wide variety of climatic applications to study environmental issues related to flood and global warming in Malaysia.

SEA LEVEL VARIATION AND GEOSTROPHIC CURRENT OF THE SUNDA STRAIT BASED ON TIDAL AND WIND DATA IN YEAR 2008

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Resni Oktavia ◽  
John Iskandar Pariwono ◽  
Parluhutan Manurung
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Tide Gauge ◽  
High Tide ◽  
Level Variation ◽  
Tidal Forces ◽  
Sea Level Variation ◽  
The Indian Ocean ◽  
Java Sea ◽  
Current Flows

Sea level variation from four tide-gauge data in the Sunda Strait, Indonesia, in the year 2008 has been studied by using Wavelet 1 D Daubechius 1 level 5 type and Fast Fourier Transform methods. The hourly sea level variation in April and November (representing transitional seasonal conditions) is approximately +0.49 m; whereas in January (representing Northwest Monsoon condition) and July (representing Southeast Monsoon condition) can reach up to -0.48 m. In 2008, sea level variation in the Sunda Strait is mainly influenced by the monsoon. Results from this study show that there are at least three phenomena of sea level variations in the Sunda Strait, namely (1) seasonal variation (periodicity between 4-6 months) where it is believed influenced by the Java Sea; (2) intra-seasonal (periodicity between 1-3 months), which is more influenced by the Indian Ocean; and (3) tidal forcing (periodicity between 14-17 days, suggesting fortnightly tidal forces) which propagates from the Indian Ocean into the Sunda Strait. Result from surface geostrophic approximation calculation suggests that during Southeast Monsoon (June-August), monthly mean current flows southwestwardly towards the Indian Ocean with a velocity of 0.14-0.16 m/s. Whereas during Northwest monsoon (December-February), current flows northeastwardly towards the Java Sea with a velocity of 0.14-0.17 m/s. Furthermore, on the daily time scale, tidal current in the Sunda Strait flows into the Java Sea (Indian Ocean) during high tide (low tide) with a velocity ranging from 0.51 to 0.72 m/s (0.48 to 0.51 m/s).Keywords: sea level variation, geostrophic approximation, tides, monsoon, Sunda Strait

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