[sentence A]。その上、[sentence B]。
[sentence A]。その上 + [sentence B]。
Note: Used as a conjunction connecting two sentences. Sentence B reinforces or adds to the same direction (positive + positive, or negative + negative) as Sentence A.
その上 (そのうえ) is a conjunction meaning "besides," "in addition," "furthermore," or "moreover." It is used to add information that reinforces or builds upon what was already stated in the previous clause or sentence. The added information typically goes in the same direction as what came before – either stacking positive points on positive, or negative on negative.
When the first statement is positive, その上 introduces an additional positive point.
When the first statement is negative, その上 piles on further negative information.
It is similar in meaning to さらに (furthermore) and しかも (moreover), but その上 tends to feel slightly more formal and deliberate in connecting the two points.
Unlike それに, which is more conversational, その上 is commonly found in both spoken and written Japanese, especially in compositions and formal speech.
Be careful not to use その上 to connect contrasting ideas – for that, use そのかわり代わりor しかし instead.