The word "up-surges" refers to a sudden and rapid increase in something, such as prices or emotions. When looking for antonyms, some suitable words could be "decline", "decrease", "diminish", "reduce", "plunge", or "slump". These words signify a decrease or a drop in the level or intensity of something. For instance, if we talk about the stock market, the antonym of an "up-surge" would be a "decline" or a "slump". Similarly, if we refer to emotions, "reduce" or "diminish" could be an appropriate antonym. Therefore, while "up-surge" represents an upward trend, its antonyms convey a downward trend.