A proxy study is able to show a certain side (1) of scientific "truth". There are caveats with proxy-studies.

Measuring oceanic currents show another side (2) of scientific "truth". There are caveats there too (see below).

Finally, one also could measure an oceanic current for a period of time and combine that data with a proxy study to see if the one study actually makes sense to the other (3). But particularly combining data from different sources has some serious caveats.

However. The question raised above by askod was whether the Labrador current can be measured directly. My answer: It can, but recent studies show one should tread carefully how to do that.

A snapshot study of measuring oceanic currents (that is, run a transect with a boat every x years and take a measurement every y meters) should now be considered a highly unreliable method to say something about the actual truth (whatever that may be). That is the core take-away lesson from the RAPID study and hullabaloo about the MOC shutdown: oceanic currents are fickle and their dynamics are unreliably mapped by a few years of snapshot measurements.

Secondly, no one here, myself included, seems to know at this point if the study actually included oceanic current measurements - snapshot or otherwise - or combined data sets. I will give it a look if it has.

Yet if we know that a certain methodology (snapshot measurements) is insufficient to properly capture a side of scientific truth, coalescing the data would not be of any help to learn us something extra.

None of this invalidates the proxy-data (1) in any way.

Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes (δ¹⁵N) preserved in sediments and other bioarchives. Traditional bulk δ¹⁵N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids (δ¹⁵N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the δ¹⁵N variability of bulk organic matter. Here, we demonstrate the first use of δ¹⁵N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral δ¹⁵N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new δ¹⁵N-AA approach to control for variable trophic processing, we are able to interpret coral bulk δ¹⁵N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of δ¹⁵N-AA for paleoceanographic studies of the marine N cycle.