The Atlantic Ocean at the Last Glacial Maximum: 1. Objective Mapping of the GLAMAP Sea-Surface Conditions

Abstract

Recent efforts of the German paleoceanographic community have resulted in a unique data set of reconstructed sea-surface temperature for the Atlantic Ocean during the Last Glacial Maximum, plus estimates for the extents of glacial sea ice. Unlike prior attempts, the contributing research groups based their data on a common definition of the Last Glacial Maximum chronozone and used the same modern reference data for calibrating the different transfer techniques. Furthermore, the number of processed sediment cores was vastly increased. Thus the new data is a significant advance not only with respect to quality, but also to quantity. We integrate these new data and provide monthly data sets of global sea-surface temperature and ice cover, objectively interpolated onto a regular 1°x1° grid, suitable for forcing or validating numerical ocean and atmosphere models. This set is compared to an existing subjective interpolation of the same base data, in part by employing an ocean circulation model. For the latter purpose, we reconstruct sea surface salinity from the new temperature data and the available oxygen isotope measurements.

Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis

“…This has been recognized as an issue for the reconstruction of sea surface temperatures (Schäfer-Neth and Paul 2003) and it is equally an issue for climates over land. There is no strong basis for recommending one global climatology over others, but many analyses have used the CRU climatological data set for 1961-1990 as we have here.…”

Ancient DNA reveals that bowhead whale lineages survived Late Pleistocene climate change and habitat shifts

“…aquamaps.org/download/main.php. Pleistocene environmental conditions reconstructed for the last glacial maximum (B20,000 calendar years before presence) as part of the GLAMAP project 52 were used in the hind-casting scenario. We computed mean annual environmental conditions during the Pleistocene based on the available interpolated winter and summer predictions for sea surface temperature and salinity deduced from sediment core data 52 .…”

“…Pleistocene environmental conditions reconstructed for the last glacial maximum (B20,000 calendar years before presence) as part of the GLAMAP project 52 were used in the hind-casting scenario. We computed mean annual environmental conditions during the Pleistocene based on the available interpolated winter and summer predictions for sea surface temperature and salinity deduced from sediment core data 52 . As an approximation for mean annual sea ice concentration required as input by the AquaMaps model, we used the mean proportion of time a given cell had been defined to be covered by ice in the GLAMAP data set 52 .…”

“…We computed mean annual environmental conditions during the Pleistocene based on the available interpolated winter and summer predictions for sea surface temperature and salinity deduced from sediment core data 52 . As an approximation for mean annual sea ice concentration required as input by the AquaMaps model, we used the mean proportion of time a given cell had been defined to be covered by ice in the GLAMAP data set 52 . Future annual average environmental conditions for the 2091-2100 decade were based on the Special Report on Emissions A2 climate change scenario 53 .…”

Perspectives on mapping the MARGO reconstructions by variogram analysis/kriging and objective analysis

“…For the region of the Agulhas retroflection, the sampling is quite dense, but the original data show high variability on a very small spatial scale that cannot be preserved by the interpolation, which is evident from the undulating pattern in the difference field south of Africa. If this were to be changed, the original data set had to be subdivided further into smaller regions (Scha¨fer-Neth and Paul, 2003) and the VAK be carried out on a smaller scale. In the Arctic Ocean, there are two regions where the kriged field differs considerably from the WOA data set: Along the Siberian coast the gridded SSTs fall well below the freezing point, whereas they are too high in the Barents Sea (Fig.…”