关于that of的用法

关于that of的用法
They believe the data support an idea current among marine biologists,that of the "shifting baseline".
这句话的意思是：在这些海生物学家中,他们相信目前的数据支持当前的想法,那就是所谓的“转移基线”．
关于that of在这里的用法,我大体上查了一下
说法一：that of the "shifting baseline不是从句,只是一个补语修饰词
您的说法：that经常和同位语连着用,后面不一定接of,但都是“即”的意思.这里用of完全是因为idea的原因,和that没关系.
看了您的说法之后我还是不明白啊~
一、这里that是什么词性呢?
二、如果that后不一定接of的话,那这种用法为何频频出现呢?而且在句子中又翻译成什么呢?
诸如此类的句子还有很多,我把至今为止的阅读中遇到的和查到的在这里写一下,为您揭示答案提供一个参考——
1.The mummy is that of Shepenmut who was once a singer in the Temple of Thebes.（新概念四,lesson77）
2.Estimates by Moody’s Economy.com,presented in recent Congressional testimony,suggest that of the $12 trillion the government has committed to fight the financial crisis and recession,the final tab to taxpayers will approach $1.2 trillion.
3.In stature he was above the average height; his eyes were gray,his features regular and strong; his carriage that of perfect,robust health influenced by his years of army
raining.《人猿泰山》
4.Man's first occupation was that of hunter,and his first stone weapons were made for hunting.
5.the banker-customers relationship is that of debtor and creditor - who is which depending on whether the customer's account is in credit or is overdrawn.（新概念四
,lesson12）
6.What is odd is that they have perhaps most benefited from ambition—if not always
their own then that of their parents and grandparents.（考研英语2000.TEXT5）
7.In the past decade,the Janpanese divorce rate,while still well below that of the United States,has increased by more than 50 percent,and suicides have increased by naerly one—quarter.（考研英语2000.TEXT4）
我一共25分,都给您了!