The subpolar North Atlantic experienced an extreme surface freshening event during 2012–2016, which has been shown to penetrate into the upper-deep ocean and subsequently reduce both the salinity and transport of the Deep Western Boundary Current (DWBC) around Greenland. However, the evolution of this freshening signal during its transit through the Labrador Sea, i.e., prior to its southward export via the lower limb of the Atlantic Meridional Overturning Circulation, remains unclear. Using moored observations and hydrographic data, we investigate hydrographic and transport anomalies of the DWBC in the western subpolar basin, focusing on its two principal components, the Denmark Strait Overflow Water (DSOW) and the Northeast Atlantic Deep Water (NEADW). We find that a pronounced cold and fresh anomaly emerged after 2018 in both DSOW and NEADW within the East Greenland Current and can be tracked downstream into the West Greenland Current. By the time the anomaly reaches the Labrador Current, its hydrographic signature is substantially weakened, indicating significant attenuation during downstream propagation. The anomaly is more coherent in the DSOW layer, whereas property anomaly in the NEADW layer appears to be more strongly modified along the path, possibly by mixing with adjacent waters. Transport changes also differ between the two components: DSOW transport declines since 2017 consistently in the East Greenland, West Greenland, and Labrador currents, while NEADW transport decreases in the East and West Greenland currents but shows no clear decreasing trend in the Labrador Current. Collectively, these results indicate that although the recent subpolar freshening does influence the downstream DWBC, the resulting hydrographic and transport signatures are layer-dependent and undergo significant modulation prior to reaching the Labrador Sea exit.

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