The world’s largest iceberg, known as A23a, is rapidly breaking up and getting rid of very large chunks, according to scientists from the British Antarctic Survey (BAS). Originally, the iceberg covered an area of about 3,672 square kilometers and weighed nearly one trillion metric tons. It first broke away from Antarctica’s Filchner-Ronne ice shelf in 1986 and has been constantly monitored since then. 

For more than thirty years, A23a remained grounded on the Antarctic’s Weddell Sea floor, probably until it shrank just enough to loosen its grip on the seafloor. In 2020, ocean currents started pushing it away. Later, the iceberg got trapped by an underwater mountain, creating a spinning water vortex (涡旋) called a Taylor column. It broke free again last December, ran aground in March, and started drifting once more in May.

Scientists say the iceberg is now following a strong current known as the Southern Antarctic Circumpolar Current Front, moving slowly around South Georgia in a circular path. This current is expected to carry the iceberg toward the northeast into “iceberg alley”, a common route for large icebergs. Andrew Meijers, an oceanographer at BAS, mentioned that A23a is following a path similar to earlier large icebergs like A68 and A76, which also broke up near South Georgia.

Although A23a was once the largest iceberg in the world, it has now shrunk to about 1,700 square kilometers. It currently holds the title of the second-largest iceberg, but it is expected to break into smaller pieces in the coming weeks. As the southern spring begins and water temperatures rise, the iceberg will likely continue to break.

Iceberg breaking is a natural process, and it is still unclear whether climate change is causing such events to happen more often. However, it is known that warming oceans and changing currents have led to trillions of tons of ice loss from Antarctic ice shelves in recent decades. Researchers from BAS recently collected samples from seawater around A23a to study its environmental impact. They hope to understand how such giant icebergs may affect marine life and whether they will become more common in the future.

1.1.Why did A23a start moving around in 2020 after being stuck for decades?

A It became smaller.

B A ship pulled it.

C The seafloor shook.

D The weather changed.

解析：选A。A 细节理解题。第二段提到，A23a在搁浅三十多年后开始移动，很可能是因为它缩小到刚好足以减少与海底的吸附力（probably until it shrank just enough to loosen its grip on the seafloor）。故选A。

2.2.What can be inferred from Andrew Meijers’ comment about A23a’s path?

A Its route is unique.

B Its destination is predictable.

C Its behavior is unexpected.

D Its speed is increasing.

解析：选B。B 推理判断题。海洋学家Meijers提到A23a正遵循与先前冰山（A68, A76）相似的路径，并且洋流很可能将其带向东北方向的“冰山巷”，由此可推断其最终去向是可预测的，并非独特或意外。故选B。

3.3.What is causing A23a to keep breaking apart?

A Warmer water.

B Stronger winds.

C Heavy rainfall.

D Human activities.

解析：选A。A 推理判断题。第四段末尾说明，随着南半球春季开始和水温上升，冰山很可能继续破碎（As the southern spring begins and water temperatures rise, the iceberg will likely continue to break），由此推断变暖的海水是导致其持续破碎的主要原因。故选A。

4.4.What is the main purpose of the BAS researchers collecting seawater samples near A23a?

A To study ecological effects.

B To measure current speed.

C To prevent A23a from melting.

D To check water salinity.

解析：选A。A 推理判断题。最后一段表明，研究人员采集样本是为了研究冰山对环境的影响，特别是对海洋生物的影响，以及未来此类冰山是否会更常见（to study its environmental impact... how such giant icebergs may affect marine life）。故选A。