Stable isotopic composition of Antarctic and Patagonian marine mammals collected before and during industrial-scale whaling: assessing the baseline for long-term changes in the marine ecosystem.

Great Antarctic expeditions, seal hunting and whaling industries left a legacy in natural history collections. To provide the basis for analysing the impact of whaling on marine ecosystem structuring, we conducted bulk isotope analysis from specimens of baleen whales ( and ) and seals ( and ) collected between 1843 and 1951 from the South Atlantic, Patagonian waters, Southern Ocean and Antarctic coastal seas, and preserved in the collection of Natural History Museum, London. Analysis of this material indicates the pre-whaling state of these environments and changes in the trophic position (TP) of whales and seals during the period of extensive human pressure.

Change in iceberg calving behavior preceded North Sea ice shelf disintegration during the last deglaciation.

Understanding how regime shifts in iceberg calving behavior affect ice shelf stability remains a challenge for numerical models. This is an important question as we consider the fate of the ice shelves that currently buttress the Antarctic Ice Sheet and hold back the bulk of its potential upstream sea-level contribution. Using buried landforms, we demonstrate that ice shelves fringed the former British-Irish Ice Sheet (BIIS) and document their disintegration ~18,000 years ago.

Quantifying microplastics concentration of invertebrates from three Antarctic fjords.

Microplastics, small pieces of plastic measuring less than five millimeters, have spread to all ecosystems, even those in the Southern Ocean around Antarctica. In particular, microplastics have been found contaminating water in emerging fjords, or inlets created by deglaciation, along the Antarctic Peninsula. Microplastics contamination puts fjord communities, which are unique and dominated by benthic species, at high risk for microplastic exposure leading to issues with feeding, endocrine disruption, and exposure to adsorbed toxins, all of which lower fecundity and survivability.

Quantifying microplastics in fjords along the Western Antarctic Peninsula.

Microplastics are ubiquitous around the world. Microplastics have been documented around the Southern Ocean, in coastal sediments and in Antarctic marine organisms, however microplastics data for Antarctic waters remain scarce. Microplastics concentrations were characterized from fjord habitats on the Western Antarctic Peninsula where most glaciers are rapidly retreating.

Nonlinear landscape and cultural response to sea-level rise.

Rising sea levels have been associated with human migration and behavioral shifts throughout prehistory, often with an emphasis on landscape submergence and consequent societal collapse. However, the assumption that future sea-level rise will drive similar adaptive responses is overly simplistic. While the change from land to sea represents a dramatic and permanent shift for preexisting human populations, the process of change is driven by a complex set of physical and cultural processes with long transitional phases of landscape and socioeconomic change.

Natural drivers of multidecadal Arctic sea ice variability over the last millennium.

The climate varies due to human activity, natural climate cycles, and natural events external to the climate system. Understanding the different roles played by these drivers of variability is fundamental to predicting near-term climate change and changing extremes, and to attributing observed change to anthropogenic or natural factors. Natural drivers such as large explosive volcanic eruptions or multidecadal cycles in ocean circulation occur infrequently and are therefore poorly represented within the observational record.

8.2 ka event North Sea hydrography determined by bivalve shell stable isotope geochemistry.

The abrupt 8.2 ka cold event has been widely described from Greenland and North Atlantic records. However, its expression in shelf seas is poorly documented, and the temporal resolution of most marine records is inadequate to precisely determine the chronology of major events.

Surface changes in the North Atlantic meridional overturning circulation during the last millennium.

Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate.

Persistent positive North Atlantic oscillation mode dominated the Medieval Climate Anomaly.

The Medieval Climate Anomaly (MCA) was the most recent pre-industrial era warm interval of European climate, yet its driving mechanisms remain uncertain. We present here a 947-year-long multidecadal North Atlantic Oscillation (NAO) reconstruction and find a persistent positive NAO during the MCA. Supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker NAO conditions into the Little Ice Age (LIA).