If the issue is limited to one single table I'd check it's clustered key choice. Fragmentation is most often the results of page splits which are most often caused by...

As a DBA responsible for a 4TB DWH, WhereScape scares the shit out of me.

Where adding a single column to a table in the Northwind DB during a demo...

you will need to execute a manual checkpoint command in tempdb because tempdb isonly flushed when its tranlog becomes >70% full.

See http://www.sqlskills.com/BLOGS/PAUL/post/What-does-checkpoint-do-for-tempdb.aspx

does this tell you more?

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