We investigate the effect of a 120 m sea level drop on transport through the Caribbean Sea and the Florida Straits during the Last Glacial Maximum (LGM) relative to the present, using the Regional Ocean Modeling System (ROMS). A geostrophic transport estimate for the Florida Straits suggests the LGM Florida Current was weaker than today by one third assuming that the velocity at the bottom of the channel was as small as it is today. This is consistent with a decrease in the North Atlantic overturning circulation, but there are other possible reasons for a flow decrease. It is possible that a shallower LGM Florida Straits sill depth could cause the diversion of some flow from the Florida Current. Our model results show that the volume transport through the Florida Straits is slightly reduced in a lower sea level model simulation when compared to a control sea level simulation (34.8 ± 2.0 Sv versus 39.8 ± 2.3 Sv). The difference in transport is of the order of 5 Sv, likely representing a maximum limit to the LGM flow reduction due to sea level change. Therefore, the change in sill depth between the LGM and the present is unlikely to have been a cause of the entire observed flow reduction. We also use the model output to demonstrate that transport through the Florida Straits can be accurately calculated from ocean margin density data at the core locations in the work of Lund et al. (2006) and Lynch‐Stieglitz et al. (2009), provided that a sufficiently deep reference level is chosen.

Citation: Kandasamy S and Weis P (2015) Commentary: Biogeochemical analysis of ancient Pacific Cod bone suggests Hg bioaccumulation was linked to Paleo sea level rise and climate change. Over the last 21,000 years, continuous and pulsed sea level rises from its glacial minimum of ∼120 m below the present sea level have affected the continental configuration of Earth's surface and thus land-sea interactions, materials exchanges and related biogeochemical processes. In this article, Murray and co-authors investigated total concentration of mercury (Hg) and stable carbon and nitrogen isotopes (δ 13 C and δ 15 N) in the bone collagen of archeologically recovered Pacific Cod (Gadus macrocephalus) and found high levels of total Hg in bones deposited during the early-mid Holocene interval. The authors suggested that the coastal flooding likely led to increased methylation of Hg in newly submerged terrestrial land and vegetation and thus high total Hg in bones. This study provides a clue that the coastal flooding due to future climate change may have the potential to enhance the amount of Hg significantly in marine food webs in the North Pacific region. Also of interest is the increase in methylmercury in receiving waters immediately following the flooding of previously dried wetlands, as occurred at the end of the last ice age on the continental shelves. It has been well-documented in the literature that flooding of wetlands leads to release of the sequestered methylmercury (and demonstrated experimentally by Porvari and Verta, 1995); the authors have acknowledged that this is the logical explanation to the higher levels they found in the older bones. It is unfortunate, however, that the authors chose muscle tissue to analyze in modern fish for comparison with the fossil bones. Nevertheless, an understanding of historical trends in contamination is always welcome. From stable isotopes point of view, it has been inferred based on increased carbon isotopic ratios since the mid-Holocene that shelf flooding due to sea level rise must have transferred the productivity regime from an oceanic to a shelf system. Furthermore, the authors suggested that the increase in δ 13 C may have resulted to increased phytoplankton growth rates or a change from pelagic to benthic foraging regime. δ 13 C-values in both pelagic and benthic planktons are ranging roughly from −18 to −21‰ and if one includes all suspended particles, surface sediments and ice algae investigated during both summer and winter seasons in north-central Bering Sea, …

in a sea level about 120 metres (394 ft) lower than present. Earth's history of glaciation is a product of the internal variability of Earth's climate The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began around 2.58 million years ago and is ongoing. Although geologists describe this entire period up to the present as an "ice age", in popular culture this term usually refers to the most recent glacial period, or to the Pleistocene To geologists, an ice age is defined by the presence of large amounts of land-based ice. Prior to the Quaternary glaciation, land-based ice formed during at least four earlier geologic periods: the late Paleozoic (360–260 Ma), Andean-Saharan (450–420 Ma), Cryogenian (720–635 Ma) and Huronian (2,400–2,100 Ma). Within the Quaternary ice age, there were also periodic fluctuations of the total volume of land ice, the sea level, and global temperatures. During the colder episodes (referred to as glacial periods or glacials) large ice sheets at least 4 km (2.5 mi) thick at their maximum covered parts of Europe, North America, and Siberia. The shorter warm intervals between glacials, when continental glaciers retreated, are referred to as interglacials. These are evidenced by buried soil profiles, peat beds, and lake and stream deposits separating the unsorted, unstratified deposits of glacial debris. Initially the glacial/interglacial cycle length was about 41,000 years, but following the Mid-Pleistocene Transition about 1 Ma, it slowed to about 100,000 years, as evidenced most clearly by ice cores for the…

Ice age An ice age is a period that for a long time the temperature of Earth's climate is very low. That leads to an expansion of the continental ice sheets, polar ice sheets and mountain glaciers. 'Ice age' is a term used in palaeoclimatology for the period of extensive ice sheets in the recent Pleistocene period. We now know that ice ages have happened a number of times in the past, the greatest and longest of which took place in the Proterozoic era, before multicellular eukaryotes evolved.[1][2] During ice ages, the sea level drops as water is held in the great ice sheets at the poles. How much it drops depends on several factors, such as the length of time that a cold period lasts. Stages Within an ice age, there are stages. The longer cold stages are called glacials or glacial periods. The shorter warm periods are called interglacials. The last glacial ended about 11,000 years ago, when the present interglacial started. The Greenland and Antarctic ice sheets still exist. The last two million years have been the Pleistocene ice age. During glacials, large and thick ice sheets covered much of North America and Eurasia.

Abstract A comprehensive observational database of Holocene relative sea-level (RSL) index points from northwest Europe (Belgium, the Netherlands, northwest Germany, southern North Sea) has been compiled in order to compare and reassess the data collected from the different countries/regions and by different workers on a common time–depth scale. RSL rise varies in magnitude and form between these regions, revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity. It clearly contains a non-linear, glacio- and/or hydro-isostatic subsidence component, which is only small on the Belgian coastal plain but increases significantly to a value of ca 7.5 m relative to Belgium since 8 cal. ka BP along the northwest German coast. The subsidence is at least in part related to the Post-Glacial collapse of the so-called peripheral forebulge which developed around the Fennoscandian centre of ice loading during the Last Glacial Maximum. The RSL data have been compared to geodynamic Earth models in order to infer the radial viscosity structure of the Earth's mantle underneath NW Europe (lithosphere thickness, upper- and lower-mantle viscosity), and conversely to predict RSL in regions where we have only few observational data (e.g. in the southern North Sea). A very broad range of Earth parameters fit the Belgian RSL data, suggesting that glacial isostatic adjustment (GIA) only had a minor effect on Belgian crustal dynamics during and a

<p><span>Glacial isostatic adjustment is dominated by Earth rheology resulting in a variability of relative sea-level (RSL) predictions of more than 100 meters during the last glacial cycle. Seismic tomography models reveal significant lateral variations in seismic wavespeed, most likely corresponding to variations in temperature and hence viscosity. Therefore, the replacement of 1D Earth structures by a 3D Earth structure is an essential part of recent research to reveal the impact of lateral viscosity contrasts and to achieve a more consistent view on solid-Earth dynamics. Here, we apply the VIscoelastic Lithosphere and MAntle model VILMA to predict RSL during the last deglaciation. We create an ensemble of geodynamically constrained 3D Earth structures which is based on seismic tomography models while considering a range of conversion factors to transfer seismic velocity variations into viscosity variations. For a number of globally distributed sites, we discuss the resulting variability in RSL predictions, compare this with regionally optimized 1D Earth structures, and validate the model results with relative sea-level data (sea-level indicators). This study is part of the German Climate Modeling initiative PalMod aiming the modeling of the last glacial cycle under consideration of a coupled Earth system model, i.e. including feedbacks between ice-sheets and the solid Earth.</span></p>