Arribada

• It is a Spanish word meaning “arrival by sea”.
• It refers to the mass nesting behaviour exhibited by Kemp’s Ridley and Olive Ridley sea turtles.
• There are two mass nesting sites for Olive Ridley turtles in Odisha — the Gahirmatha Marine Sanctuary and the Rushikulya coast.
• Olive Ridley turtles are protected under the Wild Life (Protection) Act, 1972, as a Schedule I species and are categorised as Vulnerable as per the IUCN Red List. 

• Hundreds of Danaine butterflies, also known as milkweed butterflies, have been tagged by a group of butterfly enthusiasts in Wayanad to track their migratory movement towards the eastern side of south India from the Western Ghats.
• Butterfly tags are tiny stickers attached to the underside of one of the hind wings.
• Each tag will have a unique code. These codes will help track the origins of the tagged butterflies if they are recaptured.

• Every year, millions of Danaine butterflies undertake the journey in South India.
• Six species of milkweed butterflies have been found in the migratory swarms.
• It is believed that they fly from the Western Ghats to the Eastern Ghats and eastern plains during March and April, before the southwest monsoon.
• The reverse migration happens before the northeast monsoon gains momentum in the Eastern Ghats, from September to November.
• This migration is believed to help the butterflies avoid heavy rains.
• An in-depth study on butterfly migration in the country is yet to be launched to know the secrets of the phenomenon.

• The Arctic winter sea ice hit its maximum extent on February 25 this year.
• This is the tenth-lowest in the satellite record maintained by the United States National Snow and Ice Data Centre (NSIDC), a Distributed Active Archive Centre of NASA.
• The loss of sea ice has primarily been observed in the Sea of Okhotsk and the Barents Sea.
•  The losses, however, have been offset by gains in the Bering Sea, Baffin Bay, and the Labrador Sea, according to NSIDC.
• At the same time, gains in the Antarctic sea ice are not enough to balance the loss in Arctic sea ice.

Sea Ice

• Sea ice is essentially frozen ocean water. All stages of winter sea ice – formation, growth, and melting – occur in the ocean, unlike icebergs, glaciers and ice shelves that originate on land.
• Sea ice in the Arctic usually reaches its peak in March. The minimum extent is usually recorded in September after it melts through the warmer months. The Antarctic sea ice in the south follows the opposite cycle.

Polar Sea Ice

• It is important to maintain global temperatures.
• Sea ice reflects 80% of the sunlight that strikes its surface, thus keeping the polar regions cool.
• Once the ice melts in the summer, the dark surface of the ocean is exposed and it absorbs 90% of the sunlight that falls on it.
• This causes a rise in the temperature of the polar region.
• Small temperature changes at the poles can lead to greater warming over time, making polar regions extremely sensitive to climate change.
•  The loss of sea ice can accelerate global warming.