LOS ANGELES  - UK pop singer Adele led the U.S. pop album chart for a second week on Wednesday, days after logging a sixth week at No. 1 in Britain.

With a little more than 520,000 copies sold in two weeks, "21" has swiftly become the year's best-selling album in the United States -- and the only set to shift more than a half-million units thus far.

It started last week at No. 1 with 352,000 -- immediately ranking it as the year's second-biggest seller behind compatriots Mumford & Sons' "Sigh No More." With another 168,000 during the sales week ended March 6, "21" jumped ahead of "Sigh" by 74,000.

Former Floetry member Marsha Ambrosius bowed at No. 2 with her debut solo set, "Late Nights & Early Mornings," which sold 96,000 copies. With her handsome start, she immediately surpassed both the sales peaks and chart highs of either of Floetry's two studio albums. The duo's first, "Floetic," topped out at No. 19 and did 41,000 in its best frame. The follow-up, "Flo'Ology," peaked at No. 7 with 77,000.

Just in time for St. Patrick's Day next Thursday, the Dropkick Murphys secured their first top 10 album -- "Going out of Style" -- entering at No. 6 with a career-high sales week of 43,000. The rollicking Irish-punk band previously charted with seven albums, going as high as No. 20 with its last studio release, "The Meanest of Times," in 2007.

Aaron Lewis, frontman for rock band Staind, also landed in the top 10 with his premiere solo effort, "Town Line." The country album opened at No. 8 with 38,000. The first single, "Country Boy," features George Jones and Charlie Daniels.

The previously mentioned Mumford & Sons' "Sigh No More" held at No. 3 (54,000), Justin Bieber's "Never Say Never: The Remixes" fell two to No. 4 (53,000), and the "Now 37" collection slipped one to No. 5 (44,000).

Bieber's "My World 2.0" fell three to No. 8 (33,000), Bruno Mars' "Doo-Wops & Hooligans" also dropped three to No. 9 (32,000), and Pink's "Greatest Hits . . . So Far!!!" rose two to No. 10 (31,000).

Overall album sales totaled 6.3 million units, down 2% compared with the previous week and up 1% compared with the comparable sales week of 2010. Year-to-date album sales stand at 52.8 million, down 8% compared with the same total at this point last year.