A complete map of the ocean subsurface temperature is essential for monitoring aspects of climate change such as the ocean heat content (OHC) and sea level changes and for understanding the dynamics ...of the ocean/climate variation. However, global observations have not been available in the past, so a mapping strategy is required to fill the data gaps. In this study, an advancedmappingmethod is proposed to reconstruct the historical ocean subsurface (0–700 m) temperature field from 1940 to 2014 by using ensemble optimal interpolation with a dynamic ensemble (EnOI-DE) approach and a multimodel ensemble of phase 5 of the Coupled Model Intercomparison Project (CMIP5) historical and representative concentration pathway 4.5 simulations. The reconstructed field is a combination of two parts: a first guess provided by the ensemble mean of CMIP5 models and an adjustment by minimizing the analysis error with the assistance of error covariance determined by the CMIP5 models. The uncertainty of the field can also be assessed. This new approach was evaluated using a series of tests, including subsample tests by using data from the Argo period, idealized tests by specifying a truth field from the models, and withdrawn-data tests by removing 20% of the observations for validation. In addition, the authors showed that the oceanmean state, long-termtrends, and interannual and decadal variability are all well represented. Furthermore, the most significant benefit of thismethod is to provide an improved estimate of the long-term historical OHC changes since 1940, which have important implications for Earth’s energy budget.
The global ocean observing system (GOOS) is an integrated system comprising various instrumental platforms distributed in different geographical locations and observing different climate regimes; ...this system is fundamental for monitoring ocean warming and climate change. This study investigated the impact of different instrument platforms on global and regional ocean heat content (OHC) estimates from 2005 to 2020 with a series of sensitivity tests, where data from one specific instrument were removed from GOOS in each test. Removing Argo, Conductivity-Temperature-Depth (CTD), eXpendable BathyThermographs (XBT), Autonomous Pinniped data (APB), Mooring and Drifting Buoys (MRB), and Glider (GLD) data led to a global 0- to 2,000-m OHC standard deviation of 18.3, 3.0, 2.8, 2.3, 1.2, and 1.2 ZJ, respectively, compared with the full-data estimate. We quantitatively verified that Argo was a central part of the GOOS since ~2005, although each system contributed substantially to climate monitoring. Argo, CTD, and XBT have near-global impacts, while the impacts of APB, MRB, and GLD are critical in specific regions, highlighting the importance of GOOS integration. The addition of the MRB to the GOOS leads to a marked positive OHC offset in the tropics, and the addition of the CTD to the GOOS leads to a systematically cold OHC offset in the boundary currents and Antarctic Circumpolar Current regions. Additionally, this study suggested the use of a better metric for effective data coverage than for determining the amount of data needed to indicate the capability of GOOS for climate monitoring. The implications for improving the current generation gap-filling method are also discussed, highlighting the importance of dealing with narrow current systems and eddy-rich regions.
How fast are the oceans warming? Cheng, Lijing; Abraham, John; Hausfather, Zeke ...
Science (American Association for the Advancement of Science),
01/2019, Letnik:
363, Številka:
6423
Journal Article
Recenzirano
Observational records of ocean heat content show that ocean warming is accelerating
Climate change from human activities mainly results from the energy imbalance in Earth's climate system caused by ...rising concentrations of heat-trapping gases. About 93% of the energy imbalance accumulates in the ocean as increased ocean heat content (OHC). The ocean record of this imbalance is much less affected by internal variability and is thus better suited for detecting and attributing human influences (
1
) than more commonly used surface temperature records. Recent observation-based estimates show rapid warming of Earth's oceans over the past few decades (see the figure) (
1
,
2
). This warming has contributed to increases in rainfall intensity, rising sea levels, the destruction of coral reefs, declining ocean oxygen levels, and declines in ice sheets; glaciers; and ice caps in the polar regions (
3
,
4
). Recent estimates of observed warming resemble those seen in models, indicating that models reliably project changes in OHC.
Detecting the response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic warming can only be made with fingerprints indirectly because of the lack of sufficiently long direct ...measurements. However, whether the relationship between the AMOC and its fingerprints is stationary is rarely examined. This study uses coupled and ocean‐alone model simulations to investigate the sensitivity of two typical AMOC fingerprints under future anthropogenic warming. We found a lower sensitivity of the North Atlantic warming hole fingerprint in future warming scenarios associated with the differing vulnerability of deep‐water origins to external forcing and climate feedback. In contrast, the remote South Atlantic salinity pile‐up fingerprint is relatively insensitive to variations in AMOC sources, and its sensitivity to the AMOC is slightly enhanced by an intensified hydrological cycle. Our study implies that fingerprints outside the northern deep convection region may become more suitable in representing the response of AMOC to future warming.
Plain Language Summary
The Atlantic meridional overturning circulation (AMOC) is an important component of the Earth's climate system. Due to the lack of sufficiently long direct measurements, the response of the AMOC to global warming has to be inferred from the AMOC fingerprints. Here we show that the sensitivity of AMOC fingerprints can be nonstationary under continuous warming scenario. It raises concerns when reconstructing AMOC change using these fingerprints in the context of climate change. Possible reasons for variations in sensitivity are further investigated. For the subpolar SST fingerprint, its sensitivity to AMOC change will be reduced as a result of differing responses of multiple deep‐water sources to global warming. The fingerprint outside the subpolar North Atlantic is less influenced by the variation in AMOC sources and can more faithfully represent the AMOC change in a warming climate.
Key Points
Relationship between Atlantic meridional overturning circulation (AMOC) fingerprints and AMOC can be nonstationary in a changing climate
Warming hole shows reduced sensitivity to AMOC in a warmer climate while the sensitivity of salinity pile‐up is slightly strengthened
Differing vulnerability of AMOC sources and changed hydrological cycle influence the sensitivity of the two fingerprints, respectively
The causes of sea-level rise since 1900 Frederikse, Thomas; Landerer, Felix; Caron, Lambert ...
Nature (London),
08/2020, Letnik:
584, Številka:
7821
Journal Article
Recenzirano
The rate of global-mean sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood
. Previous assessments found that the summed contributions of ice-mass ...loss, terrestrial water storage and thermal expansion of the ocean could not be reconciled with observed changes in global-mean sea level, implying that changes in sea level or some contributions to those changes were poorly constrained
. Recent improvements to observational data, our understanding of the main contributing processes to sea-level change and methods for estimating the individual contributions, mean another attempt at reconciliation is warranted. Here we present a probabilistic framework to reconstruct sea level since 1900 using independent observations and their inherent uncertainties. The sum of the contributions to sea-level change from thermal expansion of the ocean, ice-mass loss and changes in terrestrial water storage is consistent with the trends and multidecadal variability in observed sea level on both global and basin scales, which we reconstruct from tide-gauge records. Ice-mass loss-predominantly from glaciers-has caused twice as much sea-level rise since 1900 as has thermal expansion. Mass loss from glaciers and the Greenland Ice Sheet explains the high rates of global sea-level rise during the 1940s, while a sharp increase in water impoundment by artificial reservoirs is the main cause of the lower-than-average rates during the 1970s. The acceleration in sea-level rise since the 1970s is caused by the combination of thermal expansion of the ocean and increased ice-mass loss from Greenland. Our results reconcile the magnitude of observed global-mean sea-level rise since 1900 with estimates based on the underlying processes, implying that no additional processes are required to explain the observed changes in sea level since 1900.
Using heat to kill SARS-CoV-2 Abraham, John P; Plourde, Brian D; Cheng, Lijing
Reviews in medical virology,
September 2020, Letnik:
30, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The current coronavirus pandemic has reached global proportions and requires unparalleled collective and individual efforts to slow its spread. One critically important issue is the proper ...sterilization of physical objects that have been contaminated by the virus. Here, we review the currently existing literature on thermal inactivation of coronavirus (SARS-CoV-2) and present preliminary guideless on temperatures and exposure durations required to sterilize. We also compare these temperatures/exposure durations with potential household appliances that may be thought capable of performing sterilization.
The heat content of the upper ocean is a key climate indicator, contributing to a substantial portion of the global sea level rise. Recent ocean heat content (OHC) calculations have shown a dramatic ...shift during the period 2001–2003, which is nearly coincident with a major transition in the ocean observation network from a ship‐based system to Argo floats. Here we demonstrate that the changes in the spatial sampling of the historical observation network introduced an artificial jump during the initiation of the global Argo array (2001–2003). The start of the Argo program is responsible for such a shift. Considering the sampling bias, new methods to assess long‐term trends in the OHC (0–700 m) are proposed that suggest the presence of a continuous upper ocean warming (0.36 ± 0.08 W m−2) since 1966.
Key Points
The transfer of ocean observation system to Argo induces bias in OHC estimationThe horizontal sampling change is responsible for the sampling bias0–700 m upper ocean warming rate is assessed
Earth's energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate ...assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition, OHC changes in six major oceans are reliable on decadal time scales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.
While hurricanes occur naturally, human‐caused climate change is supercharging them and exacerbating the risk of major damage. Here using ocean and atmosphere observations, we demonstrate links ...between increased upper ocean heat content due to global warming with the extreme rainfalls from recent hurricanes. Hurricane Harvey provides an excellent case study as it was isolated in space and time. We show that prior to the beginning of northern summer of 2017, ocean heat content was the highest on record both globally and in the Gulf of Mexico, but the latter sharply decreased with hurricane Harvey via ocean evaporative cooling. The lost ocean heat was realized in the atmosphere as moisture, and then as latent heat in record‐breaking heavy rainfalls. Accordingly, record high ocean heat values not only increased the fuel available to sustain and intensify Harvey but also increased its flooding rains on land. Harvey could not have produced so much rain without human‐induced climate change. Results have implications for the role of hurricanes in climate. Proactive planning for the consequences of human‐caused climate change is not happening in many vulnerable areas, making the disasters much worse.
Plain Language Summary
Human‐induced climate change continues to warm the oceans which provide the memory of past accumulated effects. The resulting environment, including higher ocean heat content and sea surface temperatures, invigorates tropical cyclones to make them more intense, bigger, and longer lasting and greatly increases their flooding rains. The main example here is Hurricane Harvey in August 2017, which can be reasonably isolated in terms of influences on and by the environment. Hurricanes keep tropical oceans cooler as a consequence of their strong winds that increase evaporation. Here we show for the first time that the rainfall likely matches the evaporation and the corresponding ocean heat loss. Planning for such supercharged hurricanes (adaptation) by increasing resilience (e.g., better building codes and flood protection) and preparing for contingencies (such as evacuation routes, power cuts, and so forth) is essential but not adequate in many areas, including Texas, Florida, and Puerto Rico where Harvey, Irma, and Maria took their toll.
Key Points
Ocean heat content was highest on record just before northern summer of 2017, supercharging Atlantic hurricanes Harvey, Irma, and Maria
The Gulf of Mexico ocean heat loss during Harvey matched the latent heat released by Harvey rainfall and thereby fueled the storm
Essential adaptation to the natural hazards and climate change is not happening in many vulnerable areas, with major consequences
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