Marlos Goes

A climate sensitivity estimate using Bayesian fusion of instrumental observations and an Earth System model

[1] Current climate model projections are uncertain. This uncertainty is partly driven by the uncertainty in key model parameters such as climate sensitivity (CS), vertical ocean diffusivity (Kv), and strength of anthropogenic sulfate aerosol forcing. These parameters are commonly estimated using ensembles of model runs constrained by observations. Here we obtain a probability density function (pdf) of these parameters using the University of Victoria Earth System Climate Model (UVic ESCM) - an intermediate complexity model with a dynamic three-dimensional ocean. Specifically, we run an ensemble of UVic ESCM runs varying parameters that affect CS, ocean vertical diffusion, and the effects of anthropogenic sulfate aerosols. We use a statistical emulator that interpolates the UVic ESCM output to parameter settings where the model was not evaluated. We adopt a Bayesian approach to constrain the model output with instrumental surface temperature and ocean heat observations. Our approach accounts for the uncertainties in the properties of model-data residuals. We use a Markov chain Monte Carlo method to obtain a posterior pdf of these parameters. The mode of the climate sensitivity estimate is 2.8°C, with the corresponding 95% credible interval ranging from 1.8 to 4.9°C. These results are generally consistent with previous studies. The CS pdf is sensitive to the assumptions about the priors, to the effects of anthropogenic sulfate aerosols, and to the background vertical ocean diffusivity. Our method can be used with more complex climate models.

Modeled sensitivity of the Northwestern Pacific upper‐ocean response to tropical cyclones in a fully coupled climate model with varying ocean grid resolution

Tropical cyclones (TCs) actively contribute to Earth’s climate, but TC-climate interactions are largely unexplored in fully coupled models. Here we analyze the upper-ocean response to TCs using a highresolution Earth system model, in which a 0.58 atmosphere is coupled to an ocean with two different horizontal resolutions: 18 and 0.18. Both versions of the model produce realistic TC climatologies for the Northwestern Pacific region, as well as the transient surface ocean response. We examined the potential sensitivity of the coupled modeled responses to ocean grid resolution by analyzing TC-induced sea surface cooling, latent heat exchange, and basin-scale ocean heat convergence. We find that sea surface cooling and basin-scale aggregated ocean heat convergence are relatively insensitive to the horizontal ocean grid resolutions considered here, but we find key differences in the poststorm restratification processes related to mesoscale ocean eddies. We estimate the annual basin-scale TC-induced latent heat fluxes are 1.706 0.16 3 10 J and 1.436 0.16 3 10 J for the high-resolution and low-resolution model configurations, respectively, which account for roughly 45% of the total TC-induced ocean heat loss from the upper ocean. Results suggest that coupled modeling approaches capable of capturing ocean-atmosphere feedbacks are important for developing a complete understanding of the relationship between TCs and climate.

Reducing Biases in XBT Measurements by Including Discrete Information from Pressure Switches

AbstractBiases in the depth estimation of expendable bathythermograph (XBT) measurements cause considerable errors in oceanic estimates of climate variables. Efforts are currently underway to improve XBT probes by including pressure switches. Information from these pressure measurements can be used to minimize errors in the XBT depth estimation. This paper presents a simple method to correct the XBT depth biases using a number of discrete pressure measurements. A blend of controlled simulations of XBT measurements and collocated XBT/CTD data is used along with statistical methods to estimate error parameters, and to optimize the use of pressure switches in terms of number of switches, optimal depth detection, and errors in the pressure switch measurements to most efficiently correct XBT profiles. The results show that given the typical XBT depth biases, using just two pressure switches is a reliable strategy for reducing depth errors, as it uses the least number of switches for an improved accuracy and re...

Measuring the Atlantic Meridional Overturning Circulation

The Atlantic meridional overturning circulation (AMOC) plays a crucial role in redistributing heat and salt throughout the global oceans. Achieving a more complete understanding of the behavior of the AMOC system requires a comprehensive observational network that spans the entire Atlantic basin. This article describes several different types of observational systems that are used by scientists of the National Oceanographic and Atmospheric Administration and their partners at other national and international institutions to study the complex nature of the AMOC. The article also highlights several emerging technologies that will aid AMOC studies in the future.