Independent Arctic records of temperature and precipitation from the same proxy archives are rare. Nevertheless, they are important for providing detailed information on long-term climate changes and temperature-precipitation relationships in the context of large-scale atmospheric dynamics. Here, we used chironomid and cladoceran fossil assemblages to reconstruct summer air- temperature and water-level changes, during the past 400 years, in a small lake located in Finnish Lapland. Temperatures remained persistently cold over the Little Ice Age (LIA), but increased in the 20th century. After a cooler phase in the 1970s, the climate rapidly warmed to the record-high temperatures of the most recent decades. The lake-level reconstruction suggested persistently wet conditions for the LIA, followed by a dry period between ~1910 and 1970 CE, when the lake apparently became almost dry. Since the 1980s, the lake level has returned to a similar position as during the LIA. The temperature development was consistent with earlier records, but a significant local feature was found in the lake-level reconstruction – the LIA appears to have been continuously wet, without the generally depicted dry phase during the 18th and 19th centuries. Therefore, the results suggest local precipitation patterns and enforce the concept of spatially divergent LIA conditions.
A sediment core (LS-1) collected from Long Lake in King George Island, South Shetland Islands (West Antarctica) was analyzed for a variety of textural, geochemical, isotopic and paleontological properties together with 14C age dates. These data combined with published records of other studies provide a detailed history of local/regional postglacial paleoproductivity variation with respect to terrestrial paleoclimate change. The lithologic contrast of a lower diamicton and an upper fine-grained sediment demonstrates glacial recession and subsequent lake formation. The upper fine-grained deposit, intercalated by mid-Holocene tephra-fallout followed by a tephra gravity flow, was formed in a lacustrine environment. Low total organic carbon (TOC) and biogenic silica (Sibio) contents with high C/N ratios characterize the diamicton, whereas an increase of TOC and Sibio contents characterize the postglacial lacustrine fine-grained sediments, which are dated at c. 4000 yrBP. More notable are the distinct TOC maxima, which may imply enhanced primary productivity during warm periods. Changes in Sibio content and δ13C values, which support the increasing paleoproductivity, are in sympathy with these organic matter variations. The uniform and low TOC contents that are decoupled by Sibio contents are attributed to the tephra gravity flows during the evolution of the lake rather than a reduced paleoproductivity. A very recent TOC maximum is also characterized by high Sibio content and δ13C values, clearly indicating increased paleoproductivity consequent upon gradual warming across King George Island . Comparable with changes in sediment geochemistry, the occurrence and abundance of several diatom species corroborate the paleoproductivity variations together with the lithologic development. However, the paleoclimatic signature in local terrestrial lake environment during the postglacial period (for example the Long Lake) seems to be less distinct, as compared to the marine environment.