35 research outputs found
Amundsen Sea Embayment ice-sheet mass-loss predictions to 2050 calibrated using observations of velocity and elevation change
Mass loss from the Amundsen Sea Embayment of the West Antarctic Ice Sheet is a major contributor to global sea-level rise (SLR) and has been increasing over recent decades. Predictions of future SLR are increasingly modelled using ensembles of simulations within which model parameters and external forcings are varied within credible ranges. Accurately reporting the uncertainty associated with these predictions is crucial in enabling effective planning for, and construction of defences against, rising sea levels. Calibrating model simulations against current observations of ice-sheet behaviour enables the uncertainty to be reduced. Here we calibrate an ensemble of BISICLES ice-sheet model simulations of ice loss from the Amundsen Sea Embayment using remotely sensed observations of surface elevation and ice speed. Each calibration type is shown to be capable of reducing the 90% credibility bounds of predicted contributions to SLR by 34 and 43% respectively
Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020
Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0Ā±1.9gā¬ĀÆmm to global mean sea level, with the rate of mass loss rising from 105gā¬ĀÆGtgā¬ĀÆyr-1 between 1992 and 1996 to 372gā¬ĀÆGtgā¬ĀÆyr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169Ā±9gā¬ĀÆGtgā¬ĀÆyr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86gā¬ĀÆGtgā¬ĀÆyr-1 in 2017 to 444gā¬ĀÆGtgā¬ĀÆyr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82Ā±9gā¬ĀÆGtgā¬ĀÆyr-1) and, to a lesser extent, from the Antarctic Peninsula (13Ā±5gā¬ĀÆGtgā¬ĀÆyr-1). East Antarctica remains close to a state of balance, with a small gain of 3Ā±15gā¬ĀÆGtgā¬ĀÆyr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)
Heat stored in the Earth system 1960ā2020: where does the energy go?
The Earth climate system is out of energy balance, and heat has
accumulated continuously over the past decades, warming the ocean, the land,
the cryosphere, and the atmosphere. According to the Sixth Assessment Report
by Working GroupĀ I of the Intergovernmental Panel on Climate Change,
this planetary warming over multiple decades is human-driven and results in
unprecedented and committed changes to the Earth system, with adverse
impacts for ecosystems and human systems. The Earth heat inventory provides
a measure of the Earth energy imbalance (EEI) and allows for quantifying
how much heat has accumulated in the Earth system, as well as where the heat is
stored. Here we show that the Earth system has continued to accumulate
heat, with 381Ā±61āZJ accumulated from 1971 to 2020. This is equivalent to a
heating rate (i.e., the EEI) of 0.48Ā±0.1āWāmā2. The majority,
about 89ā%, of this heat is stored in the ocean, followed by about 6ā%
on land, 1ā% in the atmosphere, and about 4ā% available for melting
the cryosphere. Over the most recent period (2006ā2020), the EEI amounts to
0.76Ā±0.2āWāmā2. The Earth energy imbalance is the most
fundamental global climate indicator that the scientific community and the
public can use as the measure of how well the world is doing in the task of
bringing anthropogenic climate change under control. Moreover, this
indicator is highly complementary to other established ones like global mean
surface temperature as it represents a robust measure of the rate of climate
change and its future commitment. We call for an implementation of the
Earth energy imbalance into the Paris Agreement's Global Stocktake based on
best available science. The Earth heat inventory in this study, updated from
von Schuckmann et al.Ā (2020), is underpinned by worldwide multidisciplinary
collaboration and demonstrates the critical importance of concerted
international efforts for climate change monitoring and community-based
recommendations and we also call for urgently needed actions for enabling
continuity, archiving, rescuing, and calibrating efforts to assure improved
and long-term monitoring capacity of the global climate observing system. The data for the Earth heat inventory are publicly available, and more details are provided in Table 4.</p
Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020
Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0Ā±1.9gā¬ĀÆmm to global mean sea level, with the rate of mass loss rising from 105gā¬ĀÆGtgā¬ĀÆyr-1 between 1992 and 1996 to 372gā¬ĀÆGtgā¬ĀÆyr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169Ā±9gā¬ĀÆGtgā¬ĀÆyr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86gā¬ĀÆGtgā¬ĀÆyr-1 in 2017 to 444gā¬ĀÆGtgā¬ĀÆyr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82Ā±9gā¬ĀÆGtgā¬ĀÆyr-1) and, to a lesser extent, from the Antarctic Peninsula (13Ā±5gā¬ĀÆGtgā¬ĀÆyr-1). East Antarctica remains close to a state of balance, with a small gain of 3Ā±15gā¬ĀÆGtgā¬ĀÆyr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)
Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020
Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0Ā±1.9āmm to global mean sea level, with the rate of mass loss rising from 105āGtāyrā1 between 1992 and 1996 to 372āGtāyrā1 between 2016 and 2020. In Greenland, the rate of mass loss is 169Ā±9āGtāyrā1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86āGtāyrā1 in 2017 to 444āGtāyrā1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82Ā±9āGtāyrā1) and, to a lesser extent, from the Antarctic Peninsula (13Ā±5āGtāyrā1). East Antarctica remains close to a state of balance, with a small gain of 3Ā±15āGtāyrā1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at https://doi.org/10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)
Iodine-129 concentration in seawater near Fukushima before and after the accident at the Fukushima Daiichi Nuclear Power Plant
Anthropogenic radionuclides were released into the environment in large quantities by the Fukushima Daiichi Nuclear Power Plant (1FNPP) accident. To evaluate accident-derived <sup>129</sup>I, the <sup>129</sup>I concentrations in seawater before and after the accident were compared. <br><br> Before the accident (2008ā2009), the <sup>129</sup>I concentrations in the western margin of the North Pacific between 32° N and 44° N showed a latitudinal gradient that was expressed as a linear function of latitude. The highest and average <sup>129</sup>I concentrations after the accident were 73 times and approximately 8 times, respectively, higher than those before the accident in this study area. Considering the distribution of <sup>129</sup>I in surface seawater, the accident-derived <sup>129</sup>I in the southern and northern stations of the 1FNPP was predominantly supplied by seawater advection and atmospheric deposition (including microbial volatilization), respectively. <br><br> As of October 2011, depth profiles of <sup>129</sup>I revealed that <sup>129</sup>I originating from the 1FNPP existed mainly in the upper 100 m depth. From the depth profiles, the cumulative inventories of accident-derived <sup>129</sup>I were estimated to be (1.6ā9.6) Ć 10<sup>12</sup> atoms m<sup>ā2</sup> in this study area. <br><br> On the basis of the <sup>129</sup>I data in the seawater near Fukushima, the effective dose of <sup>129</sup>I from seafood ingestion was much smaller than the annual dose limit
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Circulation in the Northern Japan Sea Studied Chiefly with Radiocarbon
From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.Radiocarbon concentrations in the northernmost region of the Japan Sea were observed during the summer of 2002. The averaged surface delta-14C (above 100 m depth) was 52 8, which is significantly higher compared with the values of the Pacific Ocean and Okhotsk Sea. The 14C in the deep water decreased with density, and the minimum value was 70. By analyzing 14C and other hydrographic data, we found that i) the Tsushima Warm Current Water reaches to the surface layer in the southern Tatarskiy Strait; ii) deep convection did not occur in the northernmost region, at least not after the winter of 2001-2002; and iii) the bottom water that was previously formed in this region may step down southward along the bottom slope and mix with the Japan Sea Bottom Water. Furthermore, a new water mass characterized by high salinity (>34.09 psu) was found in the subsurface layer in the area north of 46 degrees N.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
Functional effects of the hadal sea cucumber Elpidia atakama (Echinodermata: Holothuroidea, Elasipodida) reflect small-scale patterns of resource availability
Holothuroidea represent the dominant benthic megafauna in hadal trenches (similar to 6,000-11,000 m), but little is known about their behaviour and functional role at such depths. Using a time-lapse camera at 8,074 m in the Peru-Chile Trench (SE Pacific Ocean), we provide the first in situ observations of locomotory activity for the elasipodid holothurian Elpidia atakama Belyaev in Shirshov Inst Oceanol 92: 326-367, (1971). Time-lapse sequences reveal 'run and mill' behaviour whereby bouts of feeding activity are interspersed by periods of locomotion. Over the total observation period (20 h 25 min), we observed a mean (+/- SD) locomotion speed of 7.0 +/- 5.7 BL h(-1), but this increased to 10.9 +/- 7.2 BL h(-1) during active relocation and reduced to 4.8 +/- 2.9 BL h(-1) during feeding. These observations show E. atakama translocates and processes sediment at rates comparable to shallower species despite extreme hydrostatic pressure and remoteness from surface-derived food