Like other major HNLC provinces, the Equatorial Pacific is considered nutrient-limited due to lack of trace metals such as iron. The Equatorial Pacific receives approximately 7-10 times more iron from Equatorial Undercurrent (EUC) upwelling than from inputs due to settling atmospheric dust. Climate reconstructions of glacial periods using sediment proxy records have revealed that the Equatorial Pacific may have been 2.5 times more productive than the modern equatorial ocean. During these glacial periods, the Equatorial Pacific increased its export of marine new production, thus providing a sink of atmospheric carbon dioxide. The science of paleoceanography attempts to understand the interplay of glacial cycles with ocean dynamics. Paleo-oceanographers currently challenge the Aeolian Dust hypothesis which suggests that the atmospheric transport of iron-rich dust off Central and South America controls the intensity of primary production in the Equatorial Pacific. One study suggests that because EUC upwelling provides most of the bioavailable iron to the equatorial surface waters, the only method to reverse HNLC conditions is by enhancing upwelling. In other words, enhanced regional upwelling, rather than iron-rich atmospheric dust deposition, may explain why this region experiences higher primary productivity during glacial periods.