Climatically controlled chemical and biological development in Arctic lakes

We investigated the factors controlling lake evolution in Arctic ecosystems using a multiproxy paleolimnological approach on a small lake on Baffin Island, Arctic Canada. Lakewater pH was inferred from fossil diatom assemblages, whereas primary production was assessed from sediment concentrations of diatom valves and spectrally inferred chlorophyll a . Our reconstructed limnological variables registered synchronous changes and showed a close coupling to Holocene climatic fluctuations, as inferred by numerous independent paleoclimate proxies. Without exception, our highest pH and production values occurred during warm intervals, and vice‐versa. A return towards paleolimnological conditions of the warm early Holocene has occurred since the midtwentieth century, corresponding to climate warming following the Little Ice Age. Maximum recent values of our reconstructed parameters are either directly comparable to, or in some cases exceed, values attained during the Holocene Thermal Maximum, 8000–10,000 years ago. Our data suggest that climate has a first‐order influence on primary production and the regulation of in‐lake DIC dynamics (and hence on lakewater pH) through its modulation of lake ice cover. We conclude that direct forcing by climate is more important than catchment processes in controlling the chemical and biological development of ice‐dominated Arctic lake ecosystems, at the scale of the Holocene.