Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea

The Arabian Sea has undergone significant warming since the mid-20th century, highlighting the importance of assessing how decadal climate patterns influence chlorophyll-a (Chl-a) and broader marine ecosystem dynamics. This study investigates the variability of Chl-a, sea surface temperature (SST),...

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Main Authors: Muhsan Ali Kalhoro, Veeranjaneyulu Chinta, Muhammad Tahir, Chunli Liu, Lixin Zhu, Zhenlin Liang, Aidah Baloch, Jun Song
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Journal of Marine Science and Engineering
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Online Access:https://www.mdpi.com/2077-1312/13/6/1170
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author Muhsan Ali Kalhoro
Veeranjaneyulu Chinta
Muhammad Tahir
Chunli Liu
Lixin Zhu
Zhenlin Liang
Aidah Baloch
Jun Song
author_facet Muhsan Ali Kalhoro
Veeranjaneyulu Chinta
Muhammad Tahir
Chunli Liu
Lixin Zhu
Zhenlin Liang
Aidah Baloch
Jun Song
author_sort Muhsan Ali Kalhoro
collection DOAJ
description The Arabian Sea has undergone significant warming since the mid-20th century, highlighting the importance of assessing how decadal climate patterns influence chlorophyll-a (Chl-a) and broader marine ecosystem dynamics. This study investigates the variability of Chl-a, sea surface temperature (SST), and sea level anomaly (SLA) over the past three decades, and their relationships with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). The mean Chl-a concentration was 1.10 mg/m<sup>3</sup>, with peak levels exceeding 2 mg/m<sup>3</sup> between 2009 and 2013, and the lowest value (0.6 mg/m<sup>3</sup>) was recorded in 2014. Elevated Chl-a levels were consistently observed in February and March across both coastal and offshore regions. Empirical orthogonal function (EOF) analysis revealed distinct spatial patterns in Chl-a and SST, indicating dynamic regional variability. The SST increased by 0.709 °C over the past four decades, accompanied by a steady rise in the SLA of approximately 1 cm. The monthly mean Chl-a exhibited a strong inverse relationship with both the SST and SLA and a positive correlation with SST gradients (R<sup>2</sup> > 0.5). A positive correlation (R<sup>2</sup> > 0.5) was found between the PDO and Chl-a, whereas the PDO was negatively correlated with the SST and SLA. In contrast, the AMO was negatively correlated with Chl-a but positively associated with warming and SLA rise. These findings underline the contrasting roles of the PDO and AMO in modulating productivity and ocean dynamics in the Arabian Sea. This study emphasizes the need for continued monitoring to improve predictions of ecosystem responses under future climate change scenarios.
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institution Kabale University
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publishDate 2025-06-01
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spelling doaj-art-3a41a4aeaa7b4a2cbb3d0693de80fb922025-08-20T03:27:29ZengMDPI AGJournal of Marine Science and Engineering2077-13122025-06-01136117010.3390/jmse13061170Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian SeaMuhsan Ali Kalhoro0Veeranjaneyulu Chinta1Muhammad Tahir2Chunli Liu3Lixin Zhu4Zhenlin Liang5Aidah Baloch6Jun Song7Marine College, Shandong University, Weihai 264209, ChinaNingbo Institute of Digital Twin, Eastern Institute of Technology, Ningbo 315201, ChinaSchool of Space Science and Technology, Shandong University, Weihai 264209, ChinaMarine College, Shandong University, Weihai 264209, ChinaMarine College, Shandong University, Weihai 264209, ChinaMarine College, Shandong University, Weihai 264209, ChinaFaculty of Marine Sciences, Lasbela University of Agriculture, Water and Marine Sciences, Uthal 90150, PakistanOperational Oceanography Institution (OOI), Dalian Ocean University, Dalian 116023, ChinaThe Arabian Sea has undergone significant warming since the mid-20th century, highlighting the importance of assessing how decadal climate patterns influence chlorophyll-a (Chl-a) and broader marine ecosystem dynamics. This study investigates the variability of Chl-a, sea surface temperature (SST), and sea level anomaly (SLA) over the past three decades, and their relationships with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). The mean Chl-a concentration was 1.10 mg/m<sup>3</sup>, with peak levels exceeding 2 mg/m<sup>3</sup> between 2009 and 2013, and the lowest value (0.6 mg/m<sup>3</sup>) was recorded in 2014. Elevated Chl-a levels were consistently observed in February and March across both coastal and offshore regions. Empirical orthogonal function (EOF) analysis revealed distinct spatial patterns in Chl-a and SST, indicating dynamic regional variability. The SST increased by 0.709 °C over the past four decades, accompanied by a steady rise in the SLA of approximately 1 cm. The monthly mean Chl-a exhibited a strong inverse relationship with both the SST and SLA and a positive correlation with SST gradients (R<sup>2</sup> > 0.5). A positive correlation (R<sup>2</sup> > 0.5) was found between the PDO and Chl-a, whereas the PDO was negatively correlated with the SST and SLA. In contrast, the AMO was negatively correlated with Chl-a but positively associated with warming and SLA rise. These findings underline the contrasting roles of the PDO and AMO in modulating productivity and ocean dynamics in the Arabian Sea. This study emphasizes the need for continued monitoring to improve predictions of ecosystem responses under future climate change scenarios.https://www.mdpi.com/2077-1312/13/6/1170chlorophyll-adynamic factorsPacific Decadal OscillationAtlantic multidecadal oscillationthe Arabian Sea
spellingShingle Muhsan Ali Kalhoro
Veeranjaneyulu Chinta
Muhammad Tahir
Chunli Liu
Lixin Zhu
Zhenlin Liang
Aidah Baloch
Jun Song
Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
Journal of Marine Science and Engineering
chlorophyll-a
dynamic factors
Pacific Decadal Oscillation
Atlantic multidecadal oscillation
the Arabian Sea
title Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
title_full Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
title_fullStr Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
title_full_unstemmed Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
title_short Assessing Chlorophyll-a Variability and Its Relationship with Decadal Climate Patterns in the Arabian Sea
title_sort assessing chlorophyll a variability and its relationship with decadal climate patterns in the arabian sea
topic chlorophyll-a
dynamic factors
Pacific Decadal Oscillation
Atlantic multidecadal oscillation
the Arabian Sea
url https://www.mdpi.com/2077-1312/13/6/1170
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AT muhammadtahir assessingchlorophyllavariabilityanditsrelationshipwithdecadalclimatepatternsinthearabiansea
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