Navigating Munk's Abyssal Recipes: Reconciling the Paradoxes and Suggesting an Upwelling Mechanism for Bottom Water in a Flat-Bottom Ocean

TL;DR

This paper revisits Munk's abyssal recipes, resolving longstanding paradoxes in deep-ocean upwelling by proposing a new erosion-intrusion model that explains abyssal water movement in flat-bottom oceans.

Contribution

It introduces a novel erosion-intrusion model for abyssal upwelling, addressing paradoxes and expanding understanding beyond traditional theories.

Findings

No need for a globally averaged diapycnal diffusivity of O(1) cm2/s.

Estimated average rising velocity in the North Pacific abyssal waters.

The model complements existing theories, especially in flat-bottom topographies.

Abstract

Walter Munk's classical work, known as the "abyssal recipes", introduced a foundational framework for comprehending the upwelling of abyssal waters. While it has spurred numerous investigations into the complexities of deep-ocean processes from theoretical, laboratory, and field perspectives, it has also faced challenges when compared to direct observations spanning decades. Two particularly intriguing paradoxes emerge: the dichotomy of diffusivities and the conundrum of interior downwelling. This study attempts to resolve these paradoxes by examining the isopycnal displacement velocity within the dynamic framework of Munk's abyssal recipes. A relieving inference is that it seems no longer an imperative to seek a globally averaged diapycnal diffusivity of O(1) cm2/s to close the mass budget associated with the bottom-water formation rate. Through box-model experiments, a novel erosion-intrusion model is proposed to elucidate the mechanism of abyssal upwelling in flat-bottom ocean, drawing an analogy to the growth of "tree rings". Based upon this model, the average rising velocity in the abyssal North Pacific is estimated using observational data of biogeochemical tracers. The proposed model does not seek to disprove existing theories but rather acts as a complement for situations that prevailing theories may not apply, such as cases with flat-bottom topography or non-bottom-intensified diffusivity.