Explanation:

Thermohaline circulation, also known as the "Great Ocean Conveyor Belt," is a key factor in maintaining the layered structure of the Arctic Ocean. It involves the movement of ocean water based on differences in temperature (thermo) and salinity (haline). In the Arctic Ocean, cold and dense water sinks beneath warmer and less dense water, creating a layered structure that helps in retaining the various water layers in place.

• The icy waters of the Arctic Ocean have become increasingly more influenced by the comparatively balmy Atlantic waters through a process called “atlantification.” It's one of the many ways in which the fragile Arctic is being disrupted by increasing global temperatures

• The Arctic Ocean is formed of numerous water layers that remain in place thanks to the differences in salt concentration, which affect the buoyancy of the water.

• The top layer is freshwater with a low salinity, held at near freezing point, which comes from the melting of sea ice and from Arctic rivers that release into the ocean. Beneath this top slice comes a layer of saltier and warmer water from the Atlantic. In between these two layers, you can find an intermediate layer known as the Arctic halocline where the warm, salty water mixes with the cold, fresh surface layer above. Once you get beyond the warm and salty Atlantic layer, there is another water mass of cold and slightly saltier water, known as Arctic deep water.

Hence option 1st is correct.