By Categories: Editorials

*This post is technical in nature, hence better suited if you have geography as optional.

Stable oxygen isotopic composition (δ18O) of foraminifera from the sediments of the Northern Indian Ocean has been used to decipher past changes in the intensity of the South Asian Monsoon. The interpretation of planktonic foraminifera δ18O is mostly based on a combination of sea surface temperature, monsoon runoff and the global ice-volume effect.

During summer, the eastward flowing summer monsoon current carries the high salinity water from the Arabian Sea to the Bay of Bengal, whereas the Bay of Bengal receives fresh water both from direct rains and runoff from the Ganga-Brahmaputra rivers.

This low salinity water is transported from the Bay of Bengal to the southeastern Arabian Sea during winter by the winter monsoon current (WMC) driven by the dry northeasterly winds.

The West India Coastal Currents (WICC) carries this low saline water from southeastern Arabian Sea to the northern Arabian Sea (Fig. 1b).

During the winter monsoon, high precipitation occurs over southeastern India (the southern states of Tamil Nadu and southeast coastal Andhra Pradesh), while rainfall at this time is quite low over Kerala compared to the summer monsoon.

Duplessy (1982), analyzing several sediment cores from the Bay of Bengal, showed that the summer monsoon rain was significantly reduced during the Last Glacial Maximum (LGM).

Oxygen isotopes of LGM planktonic foraminifera were relatively higher, resulting from reduced freshwater discharge from the major monsoon fed Indian rivers.

Likewise, Sarkar et. al. (1990) showed that the winter monsoon rains intensified during LGM by analyzing four different species of planktonic foraminifera from a sediment core from the Eastern Arabian Sea. Kudrass et. al. (2001) showed that the runoff into the Bay of Bengal had steadily increased from 21 ka (LGM) to ~4ka.

Seawater sampling locations in the Eastern Arabian Sea (Deshpande et al., 2013), sub-divided into four regions: I 6oN-12oN, II 12oN-18oN, III 18oN-22oN and IV 4oN-10oN/79oE- 60oE. b Locations of sediment cores. Region IV marked here is smaller because high resolution analyses of sediment cores have not been reported west of this box.

Seawater sampling locations in the Eastern Arabian Sea (Deshpande et al., 2013), sub-divided into four regions: I 6oN-12oN, II 12oN-18oN, III 18oN-22oN and IV 4oN-10oN/79oE- 60oE. b Locations of sediment cores. Region IV marked here is smaller because high resolution analyses of sediment cores have not been reported west of this box.

Using a fresh data set (Deshpande et. al., 2013) of seawater δ18O and salinity from the Eastern Arabian Sea (Fig. 1a), it was investigated that the seasonal variation in the salinity-δ18O relation in the Eastern Arabian Sea, dividing the latter into four major regions (Fig. 1a), three of which fall under the influence of the WICC, and one under the influence of the WMC.

The seasonal variation in the salinity-δ18O relation for all four regions shows (except for region II that receives copious summer monsoon runoff from the Western Ghats), the summer monsoon runoff from the subcontinent to the Bay of Bengal, propelled by winter monsoon winds towards the Arabian Sea, appears to be the dominant control on the modern salinity-δ18O relation in the surface regions of the eastern Arabian Sea.


Share is Caring, Choose Your Platform!

Recent Posts

  • Darknet

    Definition:

    Darknet, also known as dark web or darknet market, refers to the part of the internet that is not indexed or accessible through traditional search engines. It is a network of private and encrypted websites that cannot be accessed through regular web browsers and requires special software and configuration to access.

    The darknet is often associated with illegal activities such as drug trafficking, weapon sales, and hacking services, although not all sites on the darknet are illegal.

    Examples:

    Examples of darknet markets include Silk Road, AlphaBay, and Dream Market, which were all shut down by law enforcement agencies in recent years.

    These marketplaces operate similarly to e-commerce websites, with vendors selling various illegal goods and services, such as drugs, counterfeit documents, and hacking tools, and buyers paying with cryptocurrency for their purchases.

    Pros :

    • Anonymity: Darknet allows users to communicate and transact with each other anonymously. Users can maintain their privacy and avoid being tracked by law enforcement agencies or other entities.
    • Access to Information: The darknet provides access to information and resources that may be otherwise unavailable or censored on the regular internet. This can include political or sensitive information that is not allowed to be disseminated through other channels.
    • Freedom of Speech: The darknet can be a platform for free speech, as users are able to express their opinions and ideas without fear of censorship or retribution.
    • Secure Communication: Darknet sites are encrypted, which means that communication between users is secure and cannot be intercepted by third parties.
    •  

    Cons:

    • Illegal Activities: Many darknet sites are associated with illegal activities, such as drug trafficking, weapon sales, and hacking services. Such activities can attract criminals and expose users to serious legal risks.
    • Scams: The darknet is a hotbed for scams, with many fake vendors and websites that aim to steal users’ personal information and cryptocurrency. The lack of regulation and oversight on the darknet means that users must be cautious when conducting transactions.
    • Security Risks: The use of the darknet can expose users to malware and other security risks, as many sites are not properly secured or monitored. Users may also be vulnerable to hacking or phishing attacks.
    • Stigma: The association of the darknet with illegal activities has created a stigma that may deter some users from using it for legitimate purposes.
     
     

    Artificial Intelligence

    Definition:

    AI, or artificial intelligence, refers to the development of computer systems that can perform tasks that would normally require human intelligence, such as recognizing speech, making decisions, and understanding natural language.

    Examples:

    • Virtual assistants: Siri, Alexa, and Google Assistant are examples of virtual assistants that use natural language processing to understand and respond to users’ queries.
    • Recommendation systems: Companies like Netflix and Amazon use AI to recommend movies and products to their users based on their browsing and purchase history.

    Pros :

    • Efficiency: AI systems can work continuously without getting tired or making errors, which can save time and resources.
    • Personalization: AI can help provide personalized recommendations and experiences for users.
    • Automation: AI can automate repetitive and tedious tasks, freeing up time for humans to focus on more complex tasks.

    Cons:

    • Job loss: AI has the potential to automate jobs previously performed by humans, leading to job loss and economic disruption.
    • Bias: AI systems can be biased due to the data they are trained on, leading to unfair or discriminatory outcomes.
    • Safety and privacy concerns: AI systems can pose safety risks if they malfunction or are used maliciously, and can also raise privacy concerns if they collect and use personal data without consent.