Highlight articles

Pleistocene glacial history of the New Zealand subantarctic islands

The New Zealand subantarctic islands, in the Pacific sector of the Southern Ocean, provide valuable records of past environmental change. We find that the Auckland Islands hosted a small ice cap around 384 000 years ago, but that there was little glaciation during the Last Glacial Maximum, around 21 000 years ago, in contrast to mainland New Zealand. This shows that the climate here is susceptible to changes in regional factors such as sea-ice expanse and the position of ocean fronts.

Late Miocene–Pliocene climate evolution recorded by the red clay cover on the Xiaoshuizi planation surface, NE Tibetan Plateau

Multiple proxies for the XSZ planation surface reveal that the climate was dry and stable during the late Miocene but became intermittently humid with more seasonality at 4.7–3.9 Ma. Regional climatic differences between the central and western CLP reveal that expansion of the paleo-EASM occurred during the early Pliocene. The warming of the high northern latitudes in response to the closure of the Panama Seaway may have been responsible for the thermodynamical enhancement of the paleo–EASM.

The Open Global Glacier Model (OGGM) v1.1

Mountain glaciers are one of the few remaining subsystems of the global climate system for which no globally applicable community-driven model exists. Here we present the Open Global Glacier Model (OGGM; www.oggm.org), developed to provide a modular and open-source numerical model framework for simulating past and future change of any glacier in the world.

The role of moisture transport for precipitation in the inter-annual and inter-daily fluctuations of the Arctic sea ice extension

Ice melting at the scale of inter-annual fluctuations against the trend is favoured by an increase in moisture transport in summer, autumn, and winter and a decrease in spring. On a daily basis extreme humidity transport increases the formation of ice in winter and decreases it in spring, summer, and autumn; in these three seasons it thus contributes to Arctic sea ice melting. These patterns differ sharply from that linked to decline, especially in summer when the opposite trend applies.

Harmonising plant functional type distributions for evaluating Earth system models

A simple but powerful method for the biomisation of plant functional type distributions is introduced and tested for six different dynamic global vegetation models based on pre-industrial and palaeo-simulations. The method facilitates the direct comparison between vegetation distributions simulated by different Earth system models and between model results and the pollen-based biome reconstructions. It is therefore a powerful tool for the evaluation of Earth system models.

Heinrich events show two-stage climate response in transient glacial simulations

Heinrich events are among the dominant modes of glacial climate variability. They are caused by massive ice discharges from the Laurentide Ice Sheet into the North Atlantic. In previous studies, the climate changes were either seen as resulting from freshwater released from the melt of the discharged icebergs or by ice sheet elevation changes. With a coupled ice sheet–climate model, we show that both effects are relevant with the freshwater effects preceding the ice sheet elevation effects.

Indian winter and summer monsoon strength over the 4.2 ka BP event in foraminifer isotope records from the Indus River delta in the Arabian Sea

A foraminifer oxygen isotope record from the northeastern Arabian Sea was used to reconstruct winter and summer monsoon strength from 5.4 to 3.0 ka. We found a 200-year period of strengthened winter monsoon (4.5–4.3 ka) that coincides with the earliest phase of the Mature Harappan period of the Indus Civilization, followed by weakened winter and summer monsoons by 4.1 ka. Aridity spanning both rainfall seasons at 4.1 ka may help to explain some of the observed archaeological shifts.

The onset of neoglaciation in Iceland and the 4.2 ka event

Compositing climate proxies in sediment from seven Iceland lakes documents abrupt summer cooling between 4.5 and 4.0 ka, statistically indistinguishable from 4.2 ka. Although the decline in summer insolation was an important factor, a combination of superposed changes in ocean circulation and explosive Icelandic volcanism were likely responsible for the abrupt perturbation recorded by our proxies. Lake and catchment proxies recovered to a colder equilibrium state following the perturbation.

ESD Ideas: Photoelectrochemical carbon removal as negative emission technology

Current CO₂ emission rates are incompatible with the 2 °C target for global warming. Negative emission technologies are therefore an important basis for climate policy scenarios. We show that photoelectrochemical CO₂ reduction might be a viable, high-efficiency alternative to biomass-based approaches, which reduce competition for arable land. To develop them, chemical reactions have to be optimized for CO₂ removal, which deviates from energetic efficiency optimization in solar fuel applications.

What climate signal is contained in decadal- to centennial-scale isotope variations from Antarctic ice cores?

Proxy data on climate variations contain noise from many sources and, for reliable estimates, we need to determine those temporal scales at which the climate signal in the proxy record dominates the noise. We developed a method to derive timescale-dependent estimates of temperature proxy signal-to-noise ratios, which we apply and discuss in the context of Antarctic ice-core records but which in general are applicable to a large set of palaeoclimate records.

CL Climate: Past, Present & Future Highlight articles

Highlight articles

Pleistocene glacial history of the New Zealand subantarctic islands

Late Miocene–Pliocene climate evolution recorded by the red clay cover on the Xiaoshuizi planation surface, NE Tibetan Plateau

The Open Global Glacier Model (OGGM) v1.1

The role of moisture transport for precipitation in the inter-annual and inter-daily fluctuations of the Arctic sea ice extension

Harmonising plant functional type distributions for evaluating Earth system models

Heinrich events show two-stage climate response in transient glacial simulations

Indian winter and summer monsoon strength over the 4.2 ka BP event in foraminifer isotope records from the Indus River delta in the Arabian Sea

The onset of neoglaciation in Iceland and the 4.2 ka event

ESD Ideas: Photoelectrochemical carbon removal as negative emission technology

What climate signal is contained in decadal- to centennial-scale isotope variations from Antarctic ice cores?

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