Hebrew dialects in the Hebrew Bible?

There are traces of different spoken dialects of Biblical Hebrew in Tanakh. The most famous one, indeed, one of the most famous incident pertaining to language in recorded history, is in Judges 12:5-6:

5 And the Gileadites took the fords of the Jordan against the Ephraimites; and it was so, that when any of the fugitives of Ephraim said: 'Let me go over,' the men of Gilead said unto him: 'Art thou an Ephraimite?' If he said: 'Nay'; 6 then said they unto him: 'Say now Shibboleth'; and he said 'Sibboleth'; for he could not frame to pronounce it right; then they laid hold on him, and slew him at the fords of the Jordan; and there fell at that time of Ephraim forty and two thousand.

In fact, this incident gave birth to the English words shibboleth and possibly sibilant (my own suspicion, anyway).

But this isn't all. Other clues about variation in pronunciation and even vocabulary are found in Tanakh.

Here are a couple of nifty examples, which I picked up in an essay by Steven Fassberg called Languages of the Bible.

There might be traces of difference in dialect in the northern kingdom of Yisrael and the southern kingdom of Yehudah. This can be discerned in Bible stories which take place in the north, such a the Elijah and Elisha narrative in Kings.

Example: in northern stories the feminine form of the Hebrew "you" ( 'at, עת) can be found written as 'aty , אתי, as in 2 Kings 4:16:

ויאמר למועד הזה כעת חיה אתי חבקת בן

This, by the way, reflects the ketibh (how it is written), while the keri (how it is read) is the more usual את. Other examples of this useage are 1 Kings 14:2 and 2 Kings 8:1. Is this definitive proof another useage in the north? I'm not sure, but its an echo.

Then there is extra-biblical evidence of a northern dialect found in an ostraca (a piece of pottery with writing on it) from Samaria. In it, "year" is written as sht, שת instead of shanah, שנה and "wine" is spelled yn, ין as opposed to yyn, יין.

Because of this evidence, its been proposed that we can understand a prophecy of Amos in a new light. Amos 8:1-2:

כה הראני אדוני ה' והנה כלוב קיץ

ויאמר מה אתה ראה עמוס ואמר כלוב קיץ

ויאמר יהוה אליי בא הקץ אל עמי ישראל לא אוסיף עוד עבור לו

The bolded words mean "summer," which is pronounced qayitz and "end," which is pronounced qeitz. So if we understand the situation correctly, and in the north ay was contracted to ei, then we may have here a pun. Amos was using words which sounded identical to convey the message:

"Thus the Lord God showed me; and behold a basket of summer fruit. And He said: 'Amos, what seest thou?' And I said: 'A basket of summer fruit.' Then said the Lord unto me: The end is come upon My people Israel; I will not again pardon them any more."

This may have sounded quite nice in northern Biblical Hebrew--that is, if one didn't think about the message!

EDIT:

It has come to my attention that in Samaritan Hebrew the feminine "you" is none other than 'aty , אתי.