Two things emerge from the works of Jung et al. (2002) and Beasley et al. (2021):

1) Due to solar insolation, there have been decadal to centennial-scale changes in the upper oceanic water temperatures (2 to 3 deg.C) during the early Holocene in the Arabian Sea that modulated upwelling and monsoon precipitation (Jung et al., 2002);

2) Such monsoonal precipitation and upwelling changes might have occurred since the Oligocene-Miocene transition when the monsoon system got established (Beasley et al., 2021).

Our earlier work indicated short-term oscillations of phosphorus burial in the continental margins of the Arabian Sea (Phosphorus Deposition in Arabian Sea Sediments through Time - https://www.prl.res.in/~library/planetary_and_geosciences.htm that I interpreted as:

“Contrary to the widely held view that phosphorus could affect primary productivity in the long run, here we show evidence to believe that phosphorus may become a limiting nutrient on centennial to millennial scales, provided that its supply to the water column is restricted during high productivity episodes. Such evidence comes from the spectral analysis of phosphorus data obtained from the analysis of core sediments collected from the continental margin sediments of the eastern Arabian Sea. The results show century to millennial-scale oscillations in the burial flux of phosphorus to the sediments, which can be attributed to ocean circulation changes and intensification of SW monsoonal wind strength, which together modulates upwelling of remobilised nutrients and water column productivity. .........These results suggest that short-term solar oscillations can influence water column primary productivity and thereby phosphorus burial in the continental margin sediments of the Arabian Sea. When the phosphorus burial rate is high and the phosphorus supply to the water column is restricted (low river discharge and reduced upwelling), it may become a limiting nutrient. The century and millennial-scale oscillations in phosphorus burial rate imply that such a possibility can arise in the short term, contrary to the widely held belief that phosphorus limits productivity only on geological time scales.”

Now a few things have become clear. The oscillations in phosphorus burial may also have arisen from centennial-scale solar insolation changes that modulated the strength of the monsoon and the delivery of riverine supply of phosphorus. Moreover, changes in the upwelling may have regulated productivity and the observed phosphorus burial signal.

A further complication to this interpretation arises from a recent study suggesting that adsorption of phosphorus by iron oxides and its release during hypoxic events - the iron-phosphorus feedback - can drive multidecadal oscillations in hypoxia. The authors wrote:

“Our study shows that changes in the distribution of iron oxides between deep and shallow areas of the Baltic Sea led to self-sustaining variability (oscillations) in oxygen stress on decadal timescales during past intervals in the Sea’s 8000-year history. We use a model to demonstrate that under certain conditions of climate and nutrient pressure, such variability may occur naturally........” (Jilbert et al., 2021).

Therefore, more insight is needed to assess the short-term limitation of oceanic productivity by phosphorus in circulation-limited or enclosed oceanic regions.

Further reading:

Beasley, C., Kender, S., Giosan, L., Bolton, C.T., Anand, P., Leng, M.J., Nilsson‐Kerr, K., Ullmann, C.V., Hesselbo, S.P., Littler, K., 2021. Evidence of a South Asian proto‐monsoon during the Oligocene–Miocene transition. Paleoceanogr Paleoclimatol. https://doi.org/10.1029/2021PA004278

Jilbert, T., Gustafsson, B.G., Veldhuijzen, S., Reed, D.C., Helmond, N.A.G.M., Hermans, M., Slomp, C.P., 2021. Iron‐phosphorus feedbacks drive multidecadal oscillations in Baltic Sea hypoxia. Geophys Res Lett. https://doi.org/10.1029/2021GL095908

Jung, S.J.A., Davies, G.R., Ganssen, G., Kroon, D., 2002. Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene. Geochem.-Geophys.-Geosyst. 3, 1–10. https://doi.org/10.1029/2002GC000348