Evidence from North Atlantic deep sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene climate. During each of these episodes, cool, ice-bearing waters from north of Iceland were advected as far south as the latitude of Britain. At about the same times, the atmospheric circulation above Greenland changed abruptly. Pacings of the Holocene events and of abrupt climate shifts during the last glaciation are statistically the same; together, they make up a series of climate shifts with a cyclicity close to 1470 ± 500 years. The Holocene events, therefore, appear to be the most recent manifestation of a pervasive millennial-scale climate cycle operating independently of the glacial-interglacial climate state. Amplification of the cycle during the last glaciation may have been linked to the North Atlantic's thermohaline circulation.

http://science.sciencemag.org/content/sci/278/5341/1257.full.pdf

A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

/pdf/high-resolution-record-of-northern-hemisphere-climate-1flrm897o6.pdf

High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

About Dendrimers: Structure, Physical Properties, and Applications

Sea level change during the Quaternary is primarily a consequence of the cyclic growth and decay of ice sheets, resulting in a complex spatial and temporal pattern. Observations of this variability provide constraints on the timing, rates, and magnitudes of the changes in ice mass during a glacial cycle, as well as more limited information on the distribution of ice between the major ice sheets at any time. Observations of glacially induced sea level changes also provide information on the response of the mantle to surface loading on time scales of 10 3 to 10 5 years. Regional analyses indicate that the earth-response function is depth dependent as well as spatially variable. Comprehensive models of sea level change enable the migration of coastlines to be predicted during glacial cycles, including the anthropologically important period from about 60,000 to 20,000 years ago.

https://science.sciencemag.org/content/sci/292/5517/679.full.pdf

Sea Level Change Through the Last Glacial Cycle

Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the volatile tracers and allows three estimations of the transfer velocity for the same time period. The first estimation of the power dependence of gas transfer on molecular diffusivity in the marine environment is reported. This allows the impact of bubbles on estimates of the transfer velocity derived from changes in the helium/sulphur hexafluoride ratio to be assessed. Data from earlier dual tracer experiments are reinterpreted, and findings suggest that results from all dual tracer experiments are mutually consistent. The complete data set is used to test published parameterizations of gas transfer with wind speed. A gas ex- change relationship that shows a dependence on wind speed intermediate between those ofLiss and Merlivat [1986] and Wanninkhof [1992] is found to be optimal. The dual tracer data are shown to be reasonably consistent with global estimates of gas exchange based on the uptake of natural and bomb-derived radiocarbon. The degree of scatter in the data when plotted against wind speed suggests that parameters not scaling with wind speed are also influencing gas exchange rates.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999GB900091

In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers

THE ice cores recovered from central Greenland by the GRIP1,2 and GISP23 projects record 22 interstadial (warm) events during the part of the last glaciation spanning 20–105 kyr before present. The ice core from Vostok, east Antarctica, records nine interstadials during this period4,5. Here we explore links between Greenland and Antarctic climate during the last glaciation using a high-resolution chronology derived by correlating oxygen isotope data for trapped O2 in the GISP2 and Vostok cores. We find that interstadials occurred in east Antarctica whenever those in Greenland lasted longer than 2,000 years. Our results suggest that partial deglaciation and changes in ocean circulation are partly responsible for the climate teleconnection between Greenland and Antarctica. Ice older than 115 kyr in the GISP2 core shows rapid variations in the δ18O of O2 that have no counterpart in the Vostok record. The age–depth relationship, and thus the climate record, in this part of the GISP2, core appears to be significantly disturbed.

Climate correlations between Greenland and Antarctica during the past 100,000 years

A Lagrangian tracer study was performed on the west Florida shelf in April 1996 using deliberately injected trace gases. Although such studies have been performed previously, this work is the first where the deliberate tracers, in conjunction with carbon system parameters, are used to quantify changes in water column carbon inventories due to air-sea exchange and net community metabolism. The horizontal dispersion and the gas transfer velocity were determined over a period of 2 weeks from the change in both the concentrations and the concentration ratio of the two injected trace gases, sulfur hexafluoride (SF6) and helium-3 (³He). The second moment of the patch grew to 1.6 × 10³ km² over a period of 11 days. The gas transfer velocity, normalized to CO2 exchange at 20°C, was 8.4 cm hr−1 at an average wind speed, U10, of 4.4 m s−1 for the duration of the experiment, which is in good agreement with empirical estimates. Remineralization rates exceeded productivity, causing an increase in dissolved inorganic carbon of about 1 µmol kg−1 day−1 in the water column. During this period of senescence, 80% of the increase in inorganic carbon is attributed to community remineralization and 20% due to invasion of atmospheric CO2.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97GL01757

Mary Lynn Dickson

Papers

Climate correlations between Greenland and Antarctica during the past 100,000 years

Gas exchange, dispersion, and biological productivity on the west Florida shelf: Results from a Lagrangian tracer study